NV_vertex_program2

GL_NV_vertex_program2

Pat Brown, NVIDIA Corporation (pbrown 'at' nvidia.com)

Mark Kilgard, NVIDIA Corporation (mjk 'at' nvidia.com)

Copyright NVIDIA Corporation, 2000-2002.

NVIDIA Proprietary.

Implemented in CineFX (NV30) Emulation driver, August 2002.

Shipping in Release 40 NVIDIA driver for CineFX hardware, January 2003.

Last Modified Date: 05/16/2004

NVIDIA Revision: 32

287

Written based on the wording of the OpenGL 1.3 Specification and requires

OpenGL 1.3.

Written based on the wording of the NV_vertex_program extension

specification, version 1.0.

NV_vertex_program is required.

This extension further enhances the concept of vertex programmability

introduced by the NV_vertex_program extension, and extended by

NV_vertex_program1_1. These extensions create a separate vertex program

mode where the configurable vertex transformation operations in unextended

OpenGL are replaced by a user-defined program.

This extension introduces the VP2 execution environment, which extends the

VP1 execution environment introduced in NV_vertex_program. The VP2

environment provides several language features not present in previous

vertex programming execution environments:

* Branch instructions allow a program to jump to another instruction

specified in the program.

* Branching support allows for up to four levels of subroutine

calls/returns.

* A four-component condition code register allows an application to

compute a component-wise write mask at run time and apply that mask to

register writes.

* Conditional branches are supported, where the condition code register

is used to determine if a branch should be taken.

* Programmable user clipping is supported support (via the CLP0-CLP5

clip distance registers). Primitives are clipped to the area where

the interpolated clip distances are greater than or equal to zero.

* Instructions can perform a component-wise absolute value operation on

any operand load.

The VP2 execution environment provides a number of new instructions, and

extends the semantics of several instructions already defined in

NV_vertex_program.

* ARR: Operates like ARL, except that float-to-int conversion is done

by rounding. Equivalent results could be achieved (less efficiently)

in NV_vertex program using an ADD/ARL sequence and a program parameter

holding the value 0.5.

* BRA, CAL, RET: Branch, subroutine call, and subroutine return

instructions.

* COS, SIN: Adds support for high-precision sine and cosine

computations.

* FLR, FRC: Adds support for computing the floor and fractional portion

of floating-point vector components. Equivalent results could be

achieved (less efficiently) in NV_vertex_program using the EXP

instruction to compute the fractional portion of one component at a

time.

* EX2, LG2: Adds support for high-precision exponentiation and

logarithm computations.

* ARA: Adds pairs of components of an address register; useful for

looping and other operations.

* SEQ, SFL, SGT, SLE, SNE, STR: Add six new "set on" instructions,

similar to the SLT and SGE instructions defined in NV_vertex_program.

Equivalent results could be achieved (less efficiently) in

NV_vertex_program with multiple SLT, SGE, and arithmetic instructions.

* SSG: Adds a new "set sign" operation, which produces a vector holding

negative one for negative components, zero for components with a value

of zero, and positive one for positive components. Equivalent results

could be achieved (less efficiently) in NV_vertex_program with

multiple SLT, SGE, and arithmetic instructions.

* The ARL instruction is extended to operate on four components instead

of a single component.

* All instructions that produce integer or floating-point result vectors

have variants that update the condition code register based on the

result vector.

This extension also raises some of the resource limitations in the

NV_vertex_program extension.

* 256 program parameter registers (versus 96 in NV_vertex_program).

* 16 temporary registers (versus 12 in NV_vertex_program).

* Two four-component integer address registers (versus one

single-component register in NV_vertex_program).

* 256 total vertex program instructions (versus 128 in

NV_vertex_program).

* Including loops, programs can execute up to 64K instructions.

This extension builds upon the NV_vertex_program extension. Should this

specification contain selected edits to the NV_vertex_program

specification or should the specs be unified?

RESOLVED: Since NV_vertex_program and NV_vertex_program2 programs share

many features, the main section of this specification is unified and

describes both types of programs. Other sections containing

NV_vertex_program features that are unchanged by this extension will not

be edited.

How can a program use condition codes to avoid extra computations?

Consider the example of evaluating the OpenGL lighting model for a

given light. If the diffuse dot product is negative (roughly 1/2 the

time for random geometry), the only contribution to the light is

ambient. In this case, condition codes and branching can skip over a

number of unneeded instructions.

# R0 holds accumulated light color

# R2 holds normal

# R3 holds computed light vector

# R4 holds computed half vector

# c[0] holds ambient light/material product

# c[1] holds diffuse light/material product

# c[2].xyz holds specular light/material product

# c[2].w holds specular exponent

DP3C R1.x, R2, R3; # diffuse dot product

ADD R0, R0, c[0]; # accumulate ambient

BRA pointsAway (LT.x) # skip rest if diffuse dot < 0

MOV R1.w, c[2].w;

DP3 R1.y, R2, R4; # specular dot product

LIT R1, R1; # compute expontiated specular

MAD R4, c[1], R0.y; # accumulate diffuse

MAD R4, c[2], R0.z; # accumulate specular

pointsAway:

... # continue execution

How can a program use subroutines?

With subroutines, a program can encapsulate a small piece of

functionality into a subroutine and call it multiple times, as in CPU

code. Applications will need to identify the registers used to pass

data to and from the subroutine.

Subroutines could be used for applications like evaluating lighting

equations for a single light. With conditional branching and

subroutines, a variable number of lights (which could even vary

per-vertex) can be easily supported.

accumulate:

# R0 holds the accumulated result

# R1 holds the value to add

ADD R0, R1;

RET;

# Compute floor(A)*B by repeated addition using a subroutine. Yes,

# this is a stupid example.

#

# c[0] holds (A,B,0,1).

# R0 holds the accumulated result

# R1 holds B, the value to accumulate.

# R2 holds the number of iterations remaining.

MOV R0, c[0].z; # start with zero

MOV R1, c[0].y;

FLRC R2.x, c[0].x;

BRA done (LE.x);

top:

CAL accumulate;

ADDC R2.x, R2.x, -c[0].w; # decrement count

BRA top (GT.x);

done:

...

How can conventional OpenGL clip planes be supported in vertex programs?

The clip distance in the OpenGL specification can be evaluated with a

simple DP4 instruction that writes to one of the six clip distance

registers. Primitives will automatically be clipped to the half-space

where o[CLPx] >= 0, which matches the definition in the spec.

# R0 holds eye coordinates

# c[0] holds eye-space clip plane coefficients

DP4 o[CLP0].x, R0, c[0];

Note that the clip plane or clip distance volume corresponding to the

o[CLPn] register used must be enabled, or no clipping will be performed.

The clip distance registers allow for clip distance volumes to be

computed more-or-less arbitrarily. To approximate clipping to a sphere

of radius <n>, the following code can be used.

# R0 holds eye coordinates

# c[0].xyz holds sphere center

# c[0].w holds the square of the sphere radius

SUB R1.xyz, R0, c[0]; # distance vector

DP3 R1.w, R1, R1; # compute distance squared

SUB o[CLP0].x, c[0].w, R1.w; # compute r^2 - d^2

Since the clip distance is interpolated linearly over a primitive, the

clip distance evaluated at a point will represent a piecewise-linear

approximation of the true distance. The approximation will become

increasingly more accurate as the primitive is tesselated more finely.

How can looping be achieved in vertex programs?

Simple loops can be achieved using a general purpose floating-point

register component as a counter. The following code calls a function

named "function" <n> times, where <n> is specified in a program

parameter register component.

# c[0].x holds the number of iterations to execute.

# c[1].x holds the constant 1.0.

MOVC R15.x, c[0].x;

startLoop:

CAL function (GT.x); # if (counter > 0) function();

SUBC R15.x, R15.x, c[1].x; # counter = counter - 1;

BRA startLoop (GT.x); # if (counter > 0) goto start;

endLoop:

...

More complex loops (where a separate index may be needed for indexed

addressing into the program parameter array) can be achieved using the

ARA instruction, which will add the x/z and y/w components of an address

register.

# c[0].x holds the number of iterations to execute

# c[0].y holds the initial index value

# c[0].z holds the constant -1.0 (used for the iteration count)

# c[0].w holds the index step value

ARLC A1, c[0];

startLoop:

CAL function (GT.x); # if (counter > 0) function();

# Note: A1.y can be used for

# indexing in function().

ARAC A1.xy, A1; # counter = counter - 1;

# index += loopStep;

BRA startLoop (GT.x); # if (counter > 0) goto start;

endLoop:

...

Should this specification add support for vertex state programs beyond the

VP1 execution environment?

No. Vertex state programs are a little-used feature of

NV_vertex_program and don't perform particularly well. They are still

supported for compatibility with the original NV_vertex_program spec,

but they will not be extended to support new features.

How are NaN's be handled in the "set on" instructions (SEQ, SGE, SGT, SLE,

SLT, SNE)? What about MIN, MAX? SSG? When doing condition code tests?

Any of these instructions involving a NaN operand will produce a NaN

result. This behavior differs from the NV_fragment_program extension.

There, SEQ, SGE, SGT, SLE, and SLT will produce 0.0 if either operand is

a NaN, and SNE will produce 1.0 if either operand is a NaN.

For condition code updates, NaN values will result in "UN" condition

codes. All conditionals using a "UN" condition code, except "TR" and

"NE" will evaluate to false. This behavior is identical to the

functionality in NV_fragment_program.

How can the various features of this extension be used to provide skinning

functionality similar to that in ARB_vertex_blend and ARB_matrix_palette?

And how can that functionality be extended?

Assume an implementation that allows application of up to 8 matrices at

once. Further assume that v[12].xyzw and v[13].xyzw hold the set of 8

weights, and v[14].xyzw and v[15].xyzw hold the set of 8 matrix indices.

Furthermore, assume that the palette of matrices are stored/tracked at

c[0], c[4], c[8], and so on. As an additional optimization, an

application can specify that fewer than 8 matrices should be applied by

storing a negative palette index immediately after the last index is

applied.

Skinning support in this example can be provided by the following code:

ARLC A0, v[14]; # load 4 palette indices at once

DP4 R1.x, c[A0.x+0], v[0]; # 1st matrix transform

DP4 R1.y, c[A0.x+1], v[0];

DP4 R1.z, c[A0.x+2], v[0];

DP4 R1.w, c[A0.x+3], v[0];

MUL R0, R1, v[12].x; # accumulate weighted sum in R0

BRA end (LT.y); # stop on a negative matrix index

DP4 R1.x, c[A0.y+0], v[0]; # 2nd matrix transform

DP4 R1.y, c[A0.y+1], v[0];

DP4 R1.z, c[A0.y+2], v[0];

DP4 R1.w, c[A0.y+3], v[0];

MAD R0, R1, v[12].y, R0; # accumulate weighted sum in R0

BRA end (LT.z); # stop on a negative matrix index

... # 3rd and 4th matrix transform

ARLC A0, v[15]; # load next four palette indices

BRA end (LT.x);

DP4 R1.x, c[A0.x+0], v[0]; # 5th matrix transform

DP4 R1.y, c[A0.x+1], v[0];

DP4 R1.z, c[A0.x+2], v[0];

DP4 R1.w, c[A0.x+3], v[0];

MAD R0, R1, v[13].x, R0; # accumulate weighted sum in R0

BRA end (LT.y); # stop on a negative matrix index

... # 6th, 7th, and 8th matrix transform

end:

... # any additional instructions

The amount of code used by this example could further be reduced using a

subroutine performing four transformations at a time:

ARLC A0, v[14]; # load first four indices

CAL skin4; # do first four transformations

BRA end (LT); # end if any of the first 4 indices was < 0

ARLC A0, v[15]; # load second four indices

CAL skin4; # do second four transformations

end:

... # any additional instructions

Why does the RCC instruction exist?

RESOLVED: To perform numeric operations that will avoid overflow and

underflow issues.

Should the specification provide more examples?

RESOLVED: It would be nice.

None.

None.

Modify Section 2.11, Clipping (p. 39)

(modify last paragraph, p. 39) When the GL is not in vertex program mode

(section 2.14), this view volume may be further restricted by as many as n

client-defined clip planes to generate the clip volume. ...

(add before next-to-last paragraph, p. 40) When the GL is in vertex

program mode, the view volume may be restricted to the individual clip

distance volumes derived from the per-vertex clip distances (o[CLP0] -

o[CLP5]). Clip distance volumes are applied if and only if per-vertex

clip distances are not supported in the vertex program execution

environment. A point P belonging to the primitive under consideration is

in the clip distance volume numbered n if and only if

c_n(P) >= 0,

where c_n(P) is the interpolated value of the clip distance CLPn at the

point P. For point primitives, c_n(P) is simply the clip distance for the

vertex in question. For line and triangle primitives, per-vertex clip

distances are interpolated using a weighted mean, with weights derived

according to the algorithms described in sections 3.4 and 3.5.

(modify next-to-last paragraph, p.40) Client-defined clip planes or clip

distance volumes are enabled with the generic Enable command and disabled

with the Disable command. The value of the argument to either command is

CLIP PLANEi where i is an integer between 0 and n; specifying a value of i

enables or disables the plane equation with index i. The constants obey

CLIP PLANEi = CLIP PLANE0 + i.

Add Section 2.14, Vertex Programs (p. 57). This section supersedes the

similar section added in the NV_vertex_program extension and extended in

the NV_vertex_program1_1 extension.

The conventional GL vertex transformation model described in sections 2.10

through 2.13 is a configurable, but essentially hard-wired, sequence of

per-vertex computations based on a canonical set of per-vertex parameters

and vertex transformation related state such as transformation matrices,

lighting parameters, and texture coordinate generation parameters.

The general success and utility of the conventional GL vertex

transformation model reflects its basic correspondence to the typical

vertex transformation requirements of 3D applications.

However when the conventional GL vertex transformation model is not

sufficient, the vertex program mode provides a substantially more flexible

model for vertex transformation. The vertex program mode permits

applications to define their own vertex programs.

Section 2.14.1, Vertex Program Execution Environment

The vertex program execution environment is an operational model that

defines how a program is executed. The execution environment includes a

set of instructions, a set of registers, and semantic rules defining how

operations are performed. There are three vertex program execution

environments, VP1, VP1.1, and VP2. The environment names are taken from

the mandatory program prefix strings found at the beginning of all vertex

programs. The VP1.1 execution environment is a minor addition to the VP1

execution environment, so references to the VP1 execution environment

below apply to both VP1 and VP1.1 execution environments except where

otherwise noted.

The vertex program instruction set consists primarily of floating-point

4-component vector operations operating on per-vertex attributes and

program parameters. Vertex programs execute on a per-vertex basis and

operate on each vertex completely independently from the processing of

other vertices. Vertex programs execute without data hazards so results

computed in one operation can be used immediately afterwards. Vertex

programs produce a set of vertex result vectors that becomes the set of

transformed vertex parameters used by primitive assembly.

In the VP1 environment, vertex programs execute a finite fixed sequence of

instructions with no branching or looping. In the VP2 environment, vertex

programs support conditional and unconditional branches and four levels of

subroutine calls.

The vertex program register set consists of six types of registers

described in the following sections.

Section 2.14.1.1, Vertex Attribute Registers

The Vertex Attribute Registers are sixteen 4-component vector

floating-point registers containing the current vertex's per-vertex

attributes. These registers are numbered 0 through 15. These registers

are private to each vertex program invocation and are initialized at each

vertex program invocation by the current vertex attribute state specified

with VertexAttribNV commands. These registers are read-only during vertex

program execution. The VertexAttribNV commands used to update the vertex

attribute registers can be issued both outside and inside of Begin/End

pairs. Vertex program execution is provoked by updating vertex attribute

zero. Updating vertex attribute zero outside of a Begin/End pair is

ignored without generating any error (identical to the Vertex command

operation).

The commands

void VertexAttrib{1234}{sfd}NV(uint index, T coords);

void VertexAttrib{1234}{sfd}vNV(uint index, T coords);

void VertexAttrib4ubNV(uint index, T coords);

void VertexAttrib4ubvNV(uint index, T coords);

specify the particular current vertex attribute indicated by index.

The coordinates for each vertex attribute are named x, y, z, and w.

The VertexAttrib1NV family of commands sets the x coordinate to the

provided single argument while setting y and z to 0 and w to 1.

Similarly, VertexAttrib2NV sets x and y to the specified values,

z to 0 and w to 1; VertexAttrib3NV sets x, y, and z, with w set

to 1, and VertexAttrib4NV sets all four coordinates. The error

INVALID_VALUE is generated if index is greater than 15.

No conversions are applied to the vertex attributes specified as

type short, float, or double. However, vertex attributes specified

as type ubyte are converted as described by Table 2.6.

The commands

void VertexAttribs{1234}{sfd}vNV(uint index, sizei n, T coords[]);

void VertexAttribs4ubvNV(uint index, sizei n, GLubyte coords[]);

specify a contiguous set of n vertex attributes. The effect of

VertexAttribs{1234}{sfd}vNV(index, n, coords)

is the same (assuming no errors) as the command sequence

#define NUM k /* where k is 1, 2, 3, or 4 components */

int i;

for (i=n-1; i>=0; i--) {

VertexAttrib{NUM}{sfd}vNV(i+index, &coords[i*NUM]);

}

VertexAttribs4ubvNV behaves similarly.

The VertexAttribNV calls equivalent to VertexAttribsNV are issued in

reverse order so that vertex program execution is provoked when index

is zero only after all the other vertex attributes have first been

specified.

The set and operation of vertex attribute registers are identical for both

VP1 and VP2 execution environment.

Section 2.14.1.2, Program Parameter Registers

The Program Parameter Registers are a set of 4-component floating-point

vector registers containing the vertex program parameters. In the VP1

execution environment, there are 96 registers, numbered 0 through 95. In

the VP2 execution environment, there are 256 registers, numbered 0 through

255. This relatively large set of registers is intended to hold

parameters such as matrices, lighting parameters, and constants required

by vertex programs. Vertex program parameter registers can be updated in

one of two ways: by the ProgramParameterNV commands outside of a

Begin/End pair or by a vertex state program executed outside of a

Begin/End pair (vertex state programs are discussed in section 2.14.3).

The commands

void ProgramParameter4fNV(enum target, uint index,

float x, float y, float z, float w)

void ProgramParameter4dNV(enum target, uint index,

double x, double y, double z, double w)

specify the particular program parameter indicated by index.

The coordinates values x, y, z, and w are assigned to the respective

components of the particular program parameter. target must be

VERTEX_PROGRAM_NV.

The commands

void ProgramParameter4dvNV(enum target, uint index, double *params);

void ProgramParameter4fvNV(enum target, uint index, float *params);

operate identically to ProgramParameter4fNV and ProgramParameter4dNV

respectively except that the program parameters are passed as an

array of four components.

The error INVALID_VALUE is generated if the specified index is greater

than or equal to the number of program parameters in the execution

environment (96 for VP1, 256 for VP2).

The commands

void ProgramParameters4dvNV(enum target, uint index,

uint num, double *params);

void ProgramParameters4fvNV(enum target, uint index,

uint num, float *params);

specify a contiguous set of num program parameters. The effect is

the same (assuming no errors) as

for (i=index; i<index+num; i++) {

ProgramParameter4{fd}vNV(target, i, ¶ms[i*4]);

}

The error INVALID_VALUE is generated if sum of <index> and <num> is

greater than the number of program parameters in the execution environment

(96 for VP1, 256 for VP2).

The program parameter registers are shared to all vertex program

invocations within a rendering context. ProgramParameterNV command

updates and vertex state program executions are serialized with respect to

vertex program invocations and other vertex state program executions.

Writes to the program parameter registers during vertex state program

execution can be maskable on a per-component basis.

The initial value of all 96 (VP1) or 256 (VP2) program parameter registers

is (0,0,0,0).

Section 2.14.1.3, Address Registers

The Address Registers are 4-component vector registers with signed 10-bit

integer components. In the VP1 execution environment, there is only a

single address register (A0) and only the x component of the register is

accessible. In the VP2 execution environment, there are two address

registers (A0 and A1), of which all four components are accessible. The

address registers are private to each vertex program invocation and are

initialized to (0,0,0,0) at every vertex program invocation. These

registers can be written during vertex program execution (but not read)

and their values can be used for as a relative offset for reading vertex

program parameter registers. Only the vertex program parameter registers

can be read using relative addressing (writes using relative addressing

are not supported).

See the discussion of relative addressing of program parameters in section

2.14.2.1 and the discussion of the ARL instruction in section 2.14.3.4.

Section 2.14.1.4, Temporary Registers

The Temporary Registers are 4-component floating-point vector registers

used to hold temporary results during vertex program execution. In the

VP1 execution environment, there are 12 temporary registers, numbered 0

through 11. In the VP2 execution environment, there are 16 temporary

registers, numbered 0 through 15. These registers are private to each

vertex program invocation and initialized to (0,0,0,0) at every vertex

program invocation. These registers can be read and written during vertex

program execution. Writes to these registers can be maskable on a

per-component basis.

In the VP2 execution environment, there is one additional temporary

pseudo-register, "CC". CC is treated as unnumbered, write-only temporary

register, whose sole purpose is to allow instructions to modify the

condition code register (section 2.14.1.6) without overwriting the

contents of any temporary register.

Section 2.14.1.5, Vertex Result Registers

The Vertex Result Registers are 4-component floating-point vector

registers used to write the results of a vertex program. There are 15

result registers in the VP1 execution environment, and 21 in the VP2

execution environment. Each register value is initialized to (0,0,0,1) at

the invocation of each vertex program. Writes to the vertex result

registers can be maskable on a per-component basis. These registers are

named in Table X.1 and further discussed below.

Vertex Result Component

Register Name Description Interpretation

-------------- --------------------------------- --------------

HPOS Homogeneous clip space position (x,y,z,w)

COL0 Primary color (front-facing) (r,g,b,a)

COL1 Secondary color (front-facing) (r,g,b,a)

BFC0 Back-facing primary color (r,g,b,a)

BFC1 Back-facing secondary color (r,g,b,a)

FOGC Fog coordinate (f,*,*,*)

PSIZ Point size (p,*,*,*)

TEX0 Texture coordinate set 0 (s,t,r,q)

TEX1 Texture coordinate set 1 (s,t,r,q)

TEX2 Texture coordinate set 2 (s,t,r,q)

TEX3 Texture coordinate set 3 (s,t,r,q)

TEX4 Texture coordinate set 4 (s,t,r,q)

TEX5 Texture coordinate set 5 (s,t,r,q)

TEX6 Texture coordinate set 6 (s,t,r,q)

TEX7 Texture coordinate set 7 (s,t,r,q)

CLP0(*) Clip distance 0 (d,*,*,*)

CLP1(*) Clip distance 1 (d,*,*,*)

CLP2(*) Clip distance 2 (d,*,*,*)

CLP3(*) Clip distance 3 (d,*,*,*)

CLP4(*) Clip distance 4 (d,*,*,*)

CLP5(*) Clip distance 5 (d,*,*,*)

Table X.1: Vertex Result Registers. (*) Registers CLP0 through CLP5, are

available only in the VP2 execution environment.

HPOS is the transformed vertex's homogeneous clip space position. The

vertex's homogeneous clip space position is converted to normalized device

coordinates and transformed to window coordinates as described at the end

of section 2.10 and in section 2.11. Further processing (subsequent to

vertex program termination) is responsible for clipping primitives

assembled from vertex program-generated vertices as described in section

2.10 but all client-defined clip planes are treated as if they are

disabled when vertex program mode is enabled.

Four distinct color results can be generated for each vertex. COL0 is the

transformed vertex's front-facing primary color. COL1 is the transformed

vertex's front-facing secondary color. BFC0 is the transformed vertex's

back-facing primary color. BFC1 is the transformed vertex's back-facing

secondary color.

Primitive coloring may operate in two-sided color mode. This behavior is

enabled and disabled by calling Enable or Disable with the symbolic value

VERTEX_PROGRAM_TWO_SIDE_NV. The selection between the back-facing colors

and the front-facing colors depends on the primitive of which the vertex

is a part. If the primitive is a point or a line segment, the

front-facing colors are always selected. If the primitive is a polygon

and two-sided color mode is disabled, the front-facing colors are

selected. If it is a polygon and two-sided color mode is enabled, then

the selection is based on the sign of the (clipped or unclipped) polygon's

signed area computed in window coordinates. This facingness determination

is identical to the two-sided lighting facingness determination described

in section 2.13.1.

The selected primary and secondary colors for each primitive are clamped

to the range [0,1] and then interpolated across the assembled primitive

during rasterization with at least 8-bit accuracy for each color

component.

FOGC is the transformed vertex's fog coordinate. The register's first

floating-point component is interpolated across the assembled primitive

during rasterization and used as the fog distance to compute per-fragment

the fog factor when fog is enabled. However, if both fog and vertex

program mode are enabled, but the FOGC vertex result register is not

written, the fog factor is overridden to 1.0. The register's other three

components are ignored.

Point size determination may operate in program-specified point size mode.

This behavior is enabled and disabled by calling Enable or Disable with

the symbolic value VERTEX_PROGRAM_POINT_SIZE_NV. If the vertex is for a

point primitive and the mode is enabled and the PSIZ vertex result is

written, the point primitive's size is determined by the clamped x

component of the PSIZ register. Otherwise (because vertex program mode is

disabled, program-specified point size mode is disabled, or because the

vertex program did not write PSIZ), the point primitive's size is

determined by the point size state (the state specified using the

PointSize command).

The PSIZ register's x component is clamped to the range zero through

either the hi value of ALIASED_POINT_SIZE_RANGE if point smoothing is

disabled or the hi value of the SMOOTH_POINT_SIZE_RANGE if point smoothing

is enabled. The register's other three components are ignored.

If the vertex is not for a point primitive, the value of the PSIZ vertex

result register is ignored.

TEX0 through TEX7 are the transformed vertex's texture coordinate sets for

texture units 0 through 7. These floating-point coordinates are

interpolated across the assembled primitive during rasterization and used

for accessing textures. If the number of texture units supported is less

than eight, the values of vertex result registers that do not correspond

to existent texture units are ignored.

CLP0 through CLP5, available only in the VP2 execution environment, are

the transformed vertex's clip distances. These floating-point coordinates

are used by post-vertex program clipping process (see section 2.11).

Section 2.14.1.6, The Condition Code Register

The VP2 execution environment provides a single four-component vector

called the condition code register. Each component of this register is

one of four enumerated values: GT (greater than), EQ (equal), LT (less

than), or UN (unordered). The condition code register can be used to mask

writes to registers and to evaluate conditional branches.

Most vertex program instructions can optionally update the condition code

register. When a vertex program instruction updates the condition code

register, a condition code component is set to LT if the corresponding

component of the result is less than zero, EQ if it is equal to zero, GT

if it is greater than zero, and UN if it is NaN (not a number).

The condition code register is initialized to a vector of EQ values each

time a vertex program executes.

There is no condition code register available in the VP1 execution

environment.

Section 2.14.1.7, Semantic Meaning for Vertex Attributes and Program

Parameters

One important distinction between the conventional GL vertex

transformation mode and the vertex program mode is that per-vertex

parameters and other state parameters in vertex program mode do not have

dedicated semantic interpretations the way that they do with the

conventional GL vertex transformation mode.

For example, in the conventional GL vertex transformation mode, the Normal

command specifies a per-vertex normal. The semantic that the Normal

command supplies a normal for lighting is established because that is how

the per-vertex attribute supplied by the Normal command is used by the

conventional GL vertex transformation mode. Similarly, other state

parameters such as a light source position have semantic interpretations

based on how the conventional GL vertex transformation model uses each

particular parameter.

In contrast, vertex attributes and program parameters for vertex programs

have no pre-defined semantic meanings. The meaning of a vertex attribute

or program parameter in vertex program mode is defined by how the vertex

attribute or program parameter is used by the current vertex program to

compute and write values to the Vertex Result Registers. This is the

reason that per-vertex attributes and program parameters for vertex

programs are numbered instead of named.

For convenience however, the existing per-vertex parameters for the

conventional GL vertex transformation mode (vertices, normals,

colors, fog coordinates, vertex weights, and texture coordinates) are

aliased to numbered vertex attributes. This aliasing is specified in

Table X.2. The table includes how the various conventional components

map to the 4-component vertex attribute components.

Vertex

Attribute Conventional Conventional

Register Per-vertex Conventional Component

Number Parameter Per-vertex Parameter Command Mapping

--------- --------------- ----------------------------------- ------------

0 vertex position Vertex x,y,z,w

1 vertex weights VertexWeightEXT w,0,0,1

2 normal Normal x,y,z,1

3 primary color Color r,g,b,a

4 secondary color SecondaryColorEXT r,g,b,1

5 fog coordinate FogCoordEXT fc,0,0,1

6 - - -

7 - - -

8 texture coord 0 MultiTexCoord(GL_TEXTURE0_ARB, ...) s,t,r,q

9 texture coord 1 MultiTexCoord(GL_TEXTURE1_ARB, ...) s,t,r,q

10 texture coord 2 MultiTexCoord(GL_TEXTURE2_ARB, ...) s,t,r,q

11 texture coord 3 MultiTexCoord(GL_TEXTURE3_ARB, ...) s,t,r,q

12 texture coord 4 MultiTexCoord(GL_TEXTURE4_ARB, ...) s,t,r,q

13 texture coord 5 MultiTexCoord(GL_TEXTURE5_ARB, ...) s,t,r,q

14 texture coord 6 MultiTexCoord(GL_TEXTURE6_ARB, ...) s,t,r,q

15 texture coord 7 MultiTexCoord(GL_TEXTURE7_ARB, ...) s,t,r,q

Table X.2: Aliasing of vertex attributes with conventional per-vertex

parameters.

Only vertex attribute zero is treated specially because it is

the attribute that provokes the execution of the vertex program;

this is the attribute that aliases to the Vertex command's vertex

coordinates.

The result of a vertex program is the set of post-transformation

vertex parameters written to the Vertex Result Registers.

All vertex programs must write a homogeneous clip space position, but

the other Vertex Result Registers can be optionally written.

Clipping and culling are not the responsibility of vertex programs because

these operations assume the assembly of multiple vertices into a

primitive. View frustum clipping is performed subsequent to vertex

program execution. Clip planes are not supported in the VP1 execution

environment. Clip planes are supported indirectly via the clip distance

(o[CLPx]) registers in the VP2 execution environment.

Section 2.14.1.8, Vertex Program Specification

Vertex programs are specified as an array of ubytes. The array is a

string of ASCII characters encoding the program.

The command

LoadProgramNV(enum target, uint id, sizei len,

const ubyte *program);

loads a vertex program when the target parameter is VERTEX_PROGRAM_NV.

Multiple programs can be loaded with different names. id names the

program to load. The name space for programs is the positive integers

(zero is reserved). The error INVALID_VALUE occurs if a program is loaded

with an id of zero. The error INVALID_OPERATION is generated if a program

is loaded for an id that is currently loaded with a program of a different

program target. Managing the program name space and binding to vertex

programs is discussed later in section 2.14.1.8.

program is a pointer to an array of ubytes that represents the program

being loaded. The length of the array is indicated by len.

A second program target type known as vertex state programs is discussed

in 2.14.4.

At program load time, the program is parsed into a set of tokens possibly

separated by white space. Spaces, tabs, newlines, carriage returns, and

comments are considered whitespace. Comments begin with the character "#"

and are terminated by a newline, a carriage return, or the end of the

program array.

The Backus-Naur Form (BNF) grammar below specifies the syntactically valid

sequences for several types of vertex programs. The set of valid tokens

can be inferred from the grammar. The token "" represents an empty string

and is used to indicate optional rules. A program is invalid if it

contains any undefined tokens or characters.

The grammar provides for three different vertex program types,

corresponding to the three vertex program execution environments. VP1,

VP1.1, and VP2 programs match the grammar rules <vp1-program>,

<vp11-program>, and <vp2-program>, respectively. Some grammar rules

correspond to features or instruction forms available only in certain

execution environments. Rules beginning with the prefix "vp1-" are

available only to VP1 and VP1.1 programs. Rules beginning with the

prefixes "vp11-" and "vp2-" are available only to VP1.1 and VP2 programs,

respectively.

<program> ::= <vp1-program>

| <vp11-program>

| <vp2-program>

<vp1-program> ::= "!!VP1.0" <programBody> "END"

<vp11-program> ::= "!!VP1.1" <programBody> "END"

<vp2-program> ::= "!!VP2.0" <programBody> "END"

<programBody> ::= <optionSequence> <programText>

<optionSequence> ::= <option> <optionSequence>

| ""

<option> ::= "OPTION" <vp11-option> ";"

| "OPTION" <vp2-option> ";"

<vp11-option> ::= "NV_position_invariant"

<vp2-option> ::= "NV_position_invariant"

<programText> ::= <programTextItem> <programText>

| ""

<programTextItem> ::= <instruction> ";"

| <vp2-instructionLabel>

<instruction> ::= <ARL-instruction>

| <VECTORop-instruction>

| <SCALARop-instruction>

| <BINop-instruction>

| <TRIop-instruction>

| <vp2-BRA-instruction>

| <vp2-RET-instruction>

| <vp2-ARA-instruction>

<ARL-instruction> ::= <vp1-ARL-instruction>

| <vp2-ARL-instruction>

<vp1-ARL-instruction> ::= "ARL" <maskedAddrReg> "," <scalarSrc>

<vp2-ARL-instruction> ::= <vp2-ARLop> <maskedAddrReg> "," <vectorSrc>

<vp2-ARLop> ::= "ARL" | "ARLC"

| "ARR" | "ARRC"

<VECTORop-instruction> ::= <VECTORop> <maskedDstReg> "," <vectorSrc>

<VECTORop> ::= "LIT"

| "MOV"

| <vp11-VECTORop>

| <vp2-VECTORop>

<vp11-VECTORop> ::= "ABS"

<vp2-VECTORop> ::= "ABSC"

| "FLR" | "FLRC"

| "FRC" | "FRCC"

| "LITC"

| "MOVC"

| "SSG" | "SSGC"

<SCALARop-instruction> ::= <SCALARop> <maskedDstReg> "," <scalarSrc>

<SCALARop> ::= "EXP"

| "LOG"

| "RCP"

| "RSQ"

| <vp11-SCALARop>

| <vp2-SCALARop>

<vp11-SCALARop> ::= "RCC"

<vp2-SCALARop> ::= "COS" | "COSC"

| "EX2" | "EX2C"

| "LG2" | "LG2C"

| "EXPC"

| "LOGC"

| "RCCC"

| "RCPC"

| "RSQC"

| "SIN" | "SINC"

<BINop-instruction> ::= <BINop> <maskedDstReg> "," <vectorSrc> ","

<vectorSrc>

<BINop> ::= "ADD"

| "DP3"

| "DP4"

| "DST"

| "MAX"

| "MIN"

| "MUL"

| "SGE"

| "SLT"

| <vp11-BINop>

| <vp2-BINop>

<vp11-BINop> ::= "DPH"

| "SUB"

<vp2-BINop> ::= "ADDC"

| "DP3C"

| "DP4C"

| "DPHC"

| "DSTC"

| "MAXC"

| "MINC"

| "MULC"

| "SEQ" | "SEQC"

| "SFL" | "SFLC"

| "SGEC"

| "SGT" | "SGTC"

| "SLTC"

| "SLE" | "SLEC"

| "SNE" | "SNEC"

| "STR" | "STRC"

| "SUBC"

<TRIop-instruction> ::= <TRIop> <maskedDstReg> "," <vectorSrc> ","

<vectorSrc> "," <vectorSrc>

<TRIop> ::= "MAD"

| <vp2-TRIop>

<vp2-TRIop> ::= "MADC"

<vp2-BRA-instruction> ::= <vp2-BRANCHop> <vp2-branchLabel>

<vp2-branchCondition>

<vp2-BRANCHop> ::= "BRA"

| "CAL"

<vp2-RET-instruction> ::= "RET" <vp2-branchCondition>

<vp2-ARA-instruction> ::= <vp2-ARAop> <maskedAddrReg> "," <addrRegister>

<vp2-ARAop> ::= "ARA" | "ARAC"

<scalarSrc> ::= <baseScalarSrc>

| <vp2-absScalarSrc>

<vp2-absScalarSrc> ::= <optionalSign> "|" <baseScalarSrc> "|"

<baseScalarSrc> ::= <optionalSign> <srcRegister> <scalarSuffix>

<vectorSrc> ::= <baseVectorSrc>

| <vp2-absVectorSrc>

<vp2-absVectorSrc> ::= <optionalSign> "|" <baseVectorSrc> "|"

<baseVectorSrc> ::= <optionalSign> <srcRegister> <swizzleSuffix>

<srcRegister> ::= <vtxAttribRegister>

| <progParamRegister>

| <tempRegister>

<maskedDstReg> ::= <dstRegister> <optionalWriteMask>

<optionalCCMask>

<dstRegister> ::= <vtxResultRegister>

| <tempRegister>

| <vp2-nullRegister>

<vp2-nullRegister> ::= "CC"

<vp2-branchCondition> ::= <optionalCCMask>

<vtxAttribRegister> ::= "v" "[" vtxAttribRegNum "]"

<vtxAttribRegNum> ::= decimal integer from 0 to 15 inclusive

| "OPOS"

| "WGHT"

| "NRML"

| "COL0"

| "COL1"

| "FOGC"

| "TEX0"

| "TEX1"

| "TEX2"

| "TEX3"

| "TEX4"

| "TEX5"

| "TEX6"

| "TEX7"

<progParamRegister> ::= <absProgParamReg>

| <relProgParamReg>

<absProgParamReg> ::= "c" "[" <progParamRegNum> "]"

<progParamRegNum> ::= <vp1-progParamRegNum>

| <vp2-progParamRegNum>

<vp1-progParamRegNum> ::= decimal integer from 0 to 95 inclusive

<vp2-progParamRegNum> ::= decimal integer from 0 to 255 inclusive

<relProgParamReg> ::= "c" "[" <scalarAddr> <relProgParamOffset> "]"

<relProgParamOffset> ::= ""

| "+" <progParamPosOffset>

| "-" <progParamNegOffset>

<progParamPosOffset> ::= <vp1-progParamPosOff>

| <vp2-progParamPosOff>

<vp1-progParamPosOff> ::= decimal integer from 0 to 63 inclusive

<vp2-progParamPosOff> ::= decimal integer from 0 to 255 inclusive

<progParamNegOffset> ::= <vp1-progParamNegOff>

| <vp2-progParamNegOff>

<vp1-progParamNegOff> ::= decimal integer from 0 to 64 inclusive

<vp2-progParamNegOff> ::= decimal integer from 0 to 256 inclusive

<tempRegister> ::= "R0" | "R1" | "R2" | "R3"

| "R4" | "R5" | "R6" | "R7"

| "R8" | "R9" | "R10" | "R11"

<vp2-tempRegister> ::= "R12" | "R13" | "R14" | "R15"

<vtxResultRegister> ::= "o" "[" <vtxResultRegName> "]"

<vtxResultRegName> ::= "HPOS"

| "COL0"

| "COL1"

| "BFC0"

| "BFC1"

| "FOGC"

| "PSIZ"

| "TEX0"

| "TEX1"

| "TEX2"

| "TEX3"

| "TEX4"

| "TEX5"

| "TEX6"

| "TEX7"

| <vp2-resultRegName>

<vp2-resultRegName> ::= "CLP0"

| "CLP1"

| "CLP2"

| "CLP3"

| "CLP4"

| "CLP5"

<scalarAddr> ::= <addrRegister> "." <addrRegisterComp>

<maskedAddrReg> ::= <addrRegister> <addrWriteMask>

<addrRegister> ::= "A0"

| <vp2-addrRegister>

<vp2-addrRegister> ::= "A1"

<addrRegisterComp> ::= "x"

| <vp2-addrRegisterComp>

<vp2-addrRegisterComp> ::= "y"

| "z"

| "w"

<addrWriteMask> ::= "." "x"

| <vp2-addrWriteMask>

<vp2-addrWriteMask> ::= ""

| "." "y"

| "." "x" "y"

| "." "z"

| "." "x" "z"

| "." "y" "z"

| "." "x" "y" "z"

| "." "w"

| "." "x" "w"

| "." "y" "w"

| "." "x" "y" "w"

| "." "z" "w"

| "." "x" "z" "w"

| "." "y" "z" "w"

| "." "x" "y" "z" "w"

<optionalSign> ::= ""

| "-"

| <vp2-optionalSign>

<vp2-optionalSign> ::= "+"

<vp2-instructionLabel> ::= <vp2-branchLabel> ":"

<vp2-branchLabel> ::= <identifier>

<optionalWriteMask> ::= ""

| "." "x"

| "." "y"

| "." "x" "y"

| "." "z"

| "." "x" "z"

| "." "y" "z"

| "." "x" "y" "z"

| "." "w"

| "." "x" "w"

| "." "y" "w"

| "." "x" "y" "w"

| "." "z" "w"

| "." "x" "z" "w"

| "." "y" "z" "w"

| "." "x" "y" "z" "w"

<optionalCCMask> ::= ""

| <vp2-ccMask>

<vp2-ccMask> ::= "(" <vp2-ccMaskRule> <swizzleSuffix> ")"

<vp2-ccMaskRule> ::= "EQ" | "GE" | "GT" | "LE" | "LT" | "NE"

| "TR" | "FL"

<scalarSuffix> ::= "." <component>

<swizzleSuffix> ::= ""

| "." <component>

| "." <component> <component>

<component> <component>

<component> ::= "x"

| "y"

| "z"

| "w"

The <identifier> rule matches a sequence of one or more letters ("A"

through "Z", "a" through "z", and "_") and digits ("0" through "9); the

first character must be a letter. The underscore ("_") counts as a

letter. Upper and lower case letters are different (names are

case-sensitive).

The <vertexAttribRegNum> rule matches both register numbers 0 through 15

and a set of mnemonics that abbreviate the aliasing of conventional

per-vertex parameters to vertex attribute register numbers. Table X.3

shows the mapping from mnemonic to vertex attribute register number and

what the mnemonic abbreviates.

Vertex Attribute

Mnemonic Register Number Meaning

-------- ---------------- --------------------

"OPOS" 0 object position

"WGHT" 1 vertex weight

"NRML" 2 normal

"COL0" 3 primary color

"COL1" 4 secondary color

"FOGC" 5 fog coordinate

"TEX0" 8 texture coordinate 0

"TEX1" 9 texture coordinate 1

"TEX2" 10 texture coordinate 2

"TEX3" 11 texture coordinate 3

"TEX4" 12 texture coordinate 4

"TEX5" 13 texture coordinate 5

"TEX6" 14 texture coordinate 6

"TEX7" 15 texture coordinate 7

Table X.3: The mapping between vertex attribute register numbers,

mnemonics, and meanings.

A vertex program fails to load if it does not write at least one component

of the HPOS register.

A vertex program fails to load in the VP1 execution environment if it

contains more than 128 instructions. A vertex program fails to load in

the VP2 execution environment if it contains more than 256 instructions.

Each block of text matching the <instruction> rule counts as an

instruction.

A vertex program fails to load if any instruction sources more than one

unique program parameter register. An instruction can match the

<progParamRegister> rule more than once only if all such matches are

identical.

A vertex program fails to load if any instruction sources more than one

unique vertex attribute register. An instruction can match the

<vtxAttribRegister> rule more than once only if all such matches refer to

the same register.

The error INVALID_OPERATION is generated if a vertex program fails to load

because it is not syntactically correct or for one of the semantic

restrictions listed above.

The error INVALID_OPERATION is generated if a program is loaded for id

when id is currently loaded with a program of a different target.

A successfully loaded vertex program is parsed into a sequence of

instructions. Each instruction is identified by its tokenized name. The

operation of these instructions when executed is defined in section

2.14.1.10.

A successfully loaded program replaces the program previously assigned to

the name specified by id. If the OUT_OF_MEMORY error is generated by

LoadProgramNV, no change is made to the previous contents of the named

program.

Querying the value of PROGRAM_ERROR_POSITION_NV returns a ubyte offset

into the last loaded program string indicating where the first error in

the program. If the program fails to load because of a semantic

restriction that cannot be determined until the program is fully scanned,

the error position will be len, the length of the program. If the program

loads successfully, the value of PROGRAM_ERROR_POSITION_NV is assigned the

value negative one.

Section 2.14.1.9, Vertex Program Binding and Program Management

The current vertex program is invoked whenever vertex attribute zero is

updated (whether by a VertexAttributeNV or Vertex command). The current

vertex program is updated by

BindProgramNV(enum target, uint id);

where target must be VERTEX_PROGRAM_NV. This binds the vertex program

named by id as the current vertex program. The error INVALID_OPERATION

is generated if id names a program that is not a vertex program

(for example, if id names a vertex state program as described in

section 2.14.4).

Binding to a nonexistent program id does not generate an error.

In particular, binding to program id zero does not generate an error.

However, because program zero cannot be loaded, program zero is

always nonexistent. If a program id is successfully loaded with a

new vertex program and id is also the currently bound vertex program,

the new program is considered the currently bound vertex program.

The INVALID_OPERATION error is generated when both vertex program

mode is enabled and Begin is called (or when a command that performs

an implicit Begin is called) if the current vertex program is

nonexistent or not valid. A vertex program may not be valid for

reasons explained in section 2.14.5.

Programs are deleted by calling

void DeleteProgramsNV(sizei n, const uint *ids);

ids contains n names of programs to be deleted. After a program

is deleted, it becomes nonexistent, and its name is again unused.

If a program that is currently bound is deleted, it is as though

BindProgramNV has been executed with the same target as the deleted

program and program zero. Unused names in ids are silently ignored,

as is the value zero.

The command

void GenProgramsNV(sizei n, uint *ids);

returns n previously unused program names in ids. These names

are marked as used, for the purposes of GenProgramsNV only,

but they become existent programs only when the are first loaded

using LoadProgramNV. The error INVALID_VALUE is generated if n

is negative.

An implementation may choose to establish a working set of programs on

which binding and ExecuteProgramNV operations (execute programs are

explained in section 2.14.4) are performed with higher performance.

A program that is currently part of this working set is said to

be resident.

The command

boolean AreProgramsResidentNV(sizei n, const uint *ids,

boolean *residences);

returns TRUE if all of the n programs named in ids are resident,

or if the implementation does not distinguish a working set. If at

least one of the programs named in ids is not resident, then FALSE is

returned, and the residence of each program is returned in residences.

Otherwise the contents of residences are not changed. If any of

the names in ids are nonexistent or zero, FALSE is returned, the

error INVALID_VALUE is generated, and the contents of residences

are indeterminate. The residence status of a single named program

can also be queried by calling GetProgramivNV with id set to the

name of the program and pname set to PROGRAM_RESIDENT_NV.

AreProgramsResidentNV indicates only whether a program is

currently resident, not whether it could not be made resident.

An implementation may choose to make a program resident only on

first use, for example. The client may guide the GL implementation

in determining which programs should be resident by requesting a

set of programs to make resident.

The command

void RequestResidentProgramsNV(sizei n, const uint *ids);

requests that the n programs named in ids should be made resident.

While all the programs are not guaranteed to become resident,

the implementation should make a best effort to make as many of

the programs resident as possible. As a result of making the

requested programs resident, program names not among the requested

programs may become non-resident. Higher priority for residency

should be given to programs listed earlier in the ids array.

RequestResidentProgramsNV silently ignores attempts to make resident

nonexistent program names or zero. AreProgramsResidentNV can be

called after RequestResidentProgramsNV to determine which programs

actually became resident.

Section 2.14.2, Vertex Program Operation

In the VP1 execution environment, there are twenty-one vertex program

instructions. Four instructions (ABS, DPH, RCC, and SUB) are available

only in the VP1.1 execution environment. The instructions and their

respective input and output parameters are summarized in Table X.4.

Instruction Inputs Output Description

----------- ------ ------ --------------------------------

ABS(*) v v absolute value

ADD v,v v add

ARL v as address register load

DP3 v,v ssss 3-component dot product

DP4 v,v ssss 4-component dot product

DPH(*) v,v ssss homogeneous dot product

DST v,v v distance vector

EXP s v exponential base 2 (approximate)

LIT v v compute light coefficients

LOG s v logarithm base 2 (approximate)

MAD v,v,v v multiply and add

MAX v,v v maximum

MIN v,v v minimum

MOV v v move

MUL v,v v multiply

RCC(*) s ssss reciprocal (clamped)

RCP s ssss reciprocal

RSQ s ssss reciprocal square root

SGE v,v v set on greater than or equal

SLT v,v v set on less than

SUB(*) v,v v subtract

Table X.4: Summary of vertex program instructions in the VP1 execution

environment. "v" indicates a floating-point vector input or output, "s"

indicates a floating-point scalar input, "ssss" indicates a scalar output

replicated across a 4-component vector, "as" indicates a single component

of an address register.

In the VP2 execution environment, are thirty-nine vertex program

instructions. Vertex program instructions may have an optional suffix of

"C" to allow an update of the condition code register (section 2.14.1.6).

For example, there are two instructions to perform vector addition, "ADD"

and "ADDC". The vertex program instructions available in the VP2

execution environment and their respective input and output parameters are

summarized in Table X.5.

Instruction Inputs Output Description

----------- ------ ------ --------------------------------

ABS[C] v v absolute value

ADD[C] v,v v add

ARA[C] av av address register add

ARL[C] v av address register load

ARR[C] v av address register load (with round)

BRA as none branch

CAL as none subroutine call

COS[C] s ssss cosine

DP3[C] v,v ssss 3-component dot product

DP4[C] v,v ssss 4-component dot product

DPH[C] v,v ssss homogeneous dot product

DST[C] v,v v distance vector

EX2[C] s ssss exponential base 2

EXP[C] s v exponential base 2 (approximate)

FLR[C] v v floor

FRC[C] v v fraction

LG2[C] s ssss logarithm base 2

LIT[C] v v compute light coefficients

LOG[C] s v logarithm base 2 (approximate)

MAD[C] v,v,v v multiply and add

MAX[C] v,v v maximum

MIN[C] v,v v minimum

MOV[C] v v move

MUL[C] v,v v multiply

RCC[C] s ssss reciprocal (clamped)

RCP[C] s ssss reciprocal

RET none none subroutine call return

RSQ[C] s ssss reciprocal square root

SEQ[C] v,v v set on equal

SFL[C] v,v v set on false

SGE[C] v,v v set on greater than or equal

SGT[C] v,v v set on greater than

SIN[C] s ssss sine

SLE[C] v,v v set on less than or equal

SLT[C] v,v v set on less than

SNE[C] v,v v set on not equal

SSG[C] v v set sign

STR[C] v,v v set on true

SUB[C] v,v v subtract

Table X.5: Summary of vertex program instructions in the VP2 execution

environment. "v" indicates a floating-point vector input or output, "s"

indicates a floating-point scalar input, "ssss" indicates a scalar output

replicated across a 4-component vector, "av" indicates a full address

register, "as" indicates a single component of an address register.

Section 2.14.2.1, Vertex Program Operands

Most vertex program instructions operate on floating-point vectors,

floating-point scalars, or integer scalars as, indicated in the grammar

(see section 2.14.1.8) by the rules <vectorSrc>, <scalarSrc>, and

<scalarAddr>, respectively.

The basic set of floating-point scalar operands is defined by the grammar

rule <baseScalarSrc>. Scalar operands are single components of vertex

attribute, program parameter, or temporary registers, as allowed by the

<srcRegister> rule. A vector component is selected by the <scalarSuffix>

rule, where the characters "x", "y", "z", and "w" select the x, y, z, and

w components, respectively, of the vector.

The basic set of floating-point vector operands is defined by the grammar

rule <baseVectorSrc>. Vector operands can be obtained from vertex

attribute, program parameter, or temporary registers as allowed by the

<srcRegister> rule.

Basic vector operands can be swizzled according to the <swizzleSuffix>

rule. In its most general form, the <swizzleSuffix> rule matches the

pattern ".????" where each question mark is replaced with one of "x", "y",

"z", or "w". For such patterns, the x, y, z, and w components of the

operand are taken from the vector components named by the first, second,

third, and fourth character of the pattern, respectively. For example, if

the swizzle suffix is ".yzzx" and the specified source contains {2,8,9,0},

the swizzled operand used by the instruction is {8,9,9,2}.

If the <swizzleSuffix> rule matches "", it is treated as though it were

".xyzw". If the <swizzleSuffix> rule matches (ignoring whitespace) ".x",

".y", ".z", or ".w", these are treated the same as ".xxxx", ".yyyy",

".zzzz", and ".wwww" respectively.

Floating-point scalar or vector operands can optionally be negated

according to the <negate> rules in <baseScalarSrc> and <baseVectorSrc>.

If the <negate> matches "-", each operand or operand component is negated.

In the VP2 execution environment, a component-wise absolute value

operation is performed on an operand if the <scalarSrc> or <vectorSrc>

rules match <vp2-absScalarSrc> or <vp2-absVectorSrc>. In this case, the

absolute value of each component of the operand is taken. In addition, if

the <negate> rule in <vp2-absScalarSrc> or <vp2-absVectorSrc> matches "-",

each component is subsequently negated.

Integer scalar operands are single components of one of the address

register vectors, as identified by the <addrRegister> rule. A vector

component is selected by the <scalarSuffix> rule in the same manner as

floating-point scalar operands. Negation and absolute value operations

are not available for integer scalar operands.

The following pseudo-code spells out the operand generation process. In

the pseudo-code, "float" and "int" are floating-point and integer scalar

types, while "floatVec" and "intVec" are four-component vectors. "source"

is the register used for the operand, matching the <srcRegister> or

<addrRegister> rules. "absolute" is TRUE if the operand matches the

<vp2-absScalarSrc> or <vp2-absVectorSrc> rules, and FALSE otherwise.

"negateBase" is TRUE if the <negate> rule in <baseScalarSrc> or

<baseVectorSrc> matches "-" and FALSE otherwise. "negateAbs" is TRUE if

the <negate> rule in <vp2-absScalarSrc> or <vp2-absVectorSrc> matches "-"

and FALSE otherwise. The ".c***", ".*c**", ".**c*", ".***c" modifiers

refer to the x, y, z, and w components obtained by the swizzle operation.

floatVec VectorLoad(floatVec source)

{

floatVec operand;

operand.x = source.c***;

operand.y = source.*c**;

operand.z = source.**c*;

operand.w = source.***c;

if (negateBase) {

operand.x = -operand.x;

operand.y = -operand.y;

operand.z = -operand.z;

operand.w = -operand.w;

}

if (absolute) {

operand.x = abs(operand.x);

operand.y = abs(operand.y);

operand.z = abs(operand.z);

operand.w = abs(operand.w);

}

if (negateAbs) {

operand.x = -operand.x;

operand.y = -operand.y;

operand.z = -operand.z;

operand.w = -operand.w;

}

return operand;

}

float ScalarLoad(floatVec source)

{

float operand;

operand = source.c***;

if (negateBase) {

operand = -operand;

}

if (absolute) {

operand = abs(operand);

}

if (negateAbs) {

operand = -operand;

}

return operand;

}

intVec AddrVectorLoad(intVec addrReg)

{

intVec operand;

operand.x = source.c***;

operand.y = source.*c**;

operand.z = source.**c*;

operand.w = source.***c;

return operand;

}

int AddrScalarLoad(intVec addrReg)

{

return source.c***;

}

If an operand is obtained from a program parameter register, by matching

the <progParamRegister> rule, the register number can be obtained by

absolute or relative addressing.

When absolute addressing is used, by matching the <absProgParamReg> rule,

the program parameter register number is the number matching the

<progParamRegNum>.

When relative addressing is used, by matching the <relProgParamReg> rule,

the program parameter register number is computed during program

execution. An index is computed by adding the integer scalar operand

specified by the <scalarAddr> rule to the positive or negative offset

specified by the <progParamOffset> rule. If <progParamOffset> matches "",

an offset of zero is used.

The following pseudo-code spells out the process of loading a program

parameter. "addrReg" refers to the address register used for relative

addressing, "absolute" is TRUE if the operand uses absolute addressing and

FALSE otherwise. "paramNumber" is the program parameter number for

absolute addressing; "paramOffset" is the program parameter offset for

relative addressing. "paramRegiser" is an array holding the complete set

of program parameter registers.

floatVec ProgramParameterLoad(intVec addrReg)

{

int index;

if (absolute) {

index = paramNumber;

} else {

index = AddrScalarLoad(addrReg) + paramOffset

}

return paramRegister[index];

}

Section 2.14.2.2, Vertex Program Destination Register Update

Most vertex program instructions write a 4-component result vector to a

single temporary, vertex result, or address register. Writes to

individual components of the destination register are controlled by

individual component write masks specified as part of the instruction. In

the VP2 execution environment, writes are additionally controlled by the a

condition code write mask, which is computed at run time.

The component write mask is specified by the <optionalWriteMask> rule

found in the <maskedDstReg> or <maskedAddrReg> rule. If the optional mask

is "", all components are enabled. Otherwise, the optional mask names the

individual components to enable. The characters "x", "y", "z", and "w"

match the x, y, z, and w components respectively. For example, an

optional mask of ".xzw" indicates that the x, z, and w components should

be enabled for writing but the y component should not. The grammar

requires that the destination register mask components must be listed in

"xyzw" order.

In the VP2 execution environment, the condition code write mask is

specified by the <optionalCCMask> rule found in the <maskedDstReg> and

<maskedAddrReg> rules. If the condition code mask matches "", all

components are enabled. Otherwise, the condition code register is loaded

and swizzled according to the swizzle codes specified by <swizzleSuffix>.

Each component of the swizzled condition code is tested according to the

rule given by <ccMaskRule>. <ccMaskRule> may have the values "EQ", "NE",

"LT", "GE", LE", or "GT", which mean to enable writes if the corresponding

condition code field evaluates to equal, not equal, less than, greater

than or equal, less than or equal, or greater than, respectively.

Comparisons involving condition codes of "UN" (unordered) evaluate to true

for "NE" and false otherwise. For example, if the condition code is

(GT,LT,EQ,GT) and the condition code mask is "(NE.zyxw)", the swizzle

operation will load (EQ,LT,GT,GT) and the mask will thus will enable

writes on the y, z, and w components. In addition, "TR" always enables

writes and "FL" always disables writes, regardless of the condition code.

Each component of the destination register is updated with the result of

the vertex program instruction if and only if the component is enabled for

writes by the component write mask, and the optional condition code mask

(if applicable). Otherwise, the component of the destination register

remains unchanged.

In the VP2 execution environment, a vertex program instruction can also

optionally update the condition code register. The condition code is

updated if the condition code register update suffix "C" is present in the

instruction. The instruction "ADDC" will update the condition code; the

otherwise equivalent instruction "ADD" will not. If condition code

updates are enabled, each component of the destination register enabled

for writes is compared to zero. The corresponding component of the

condition code is set to "LT", "EQ", or "GT", if the written component is

less than, equal to, or greater than zero, respectively. Condition code

components are set to "UN" if the written component is NaN. Values of

-0.0 and +0.0 both evaluate to "EQ". If a component of the destination

register is not enabled for writes, the corresponding condition code

component is also unchanged.

In the following example code,

# R1=(-2, 0, 2, NaN) R0 CC

MOVC R0, R1; # ( -2, 0, 2, NaN) (LT,EQ,GT,UN)

MOVC R0.xyz, R1.yzwx; # ( 0, 2, NaN, NaN) (EQ,GT,UN,UN)

MOVC R0 (NE), R1.zywx; # ( 0, 0, NaN, -2) (EQ,EQ,UN,LT)

the first instruction writes (-2,0,2,NaN) to R0 and updates the condition

code to (LT,EQ,GT,UN). The second instruction, only the "x", "y", and "z"

components of R0 and the condition code are updated, so R0 ends up with

(0,2,NaN,NaN) and the condition code ends up with (EQ,GT,UN,UN). In the

third instruction, the condition code mask disables writes to the x

component (its condition code field is "EQ"), so R0 ends up with

(0,0,NaN,-2) and the condition code ends up with (EQ,EQ,UN,LT).

The following pseudocode illustrates the process of writing a result

vector to the destination register. In the pseudocode, "instrmask" refers

to the component write mask given by the <optionalWriteMask> rule. In the

VP1 execution environment, "ccMaskRule" is always "" and "updatecc" is

always FALSE. In the VP2 execution environment, "ccMaskRule" refers to

the condition code mask rule given by <vp2-optionalCCMask> and "updatecc"

is TRUE if and only if condition code updates are enabled. "result",

"destination", and "cc" refer to the result vector, the register selected

by <dstRegister> and the condition code, respectively. Condition codes do

not exist in the VP1 execution environment.

boolean TestCC(CondCode field) {

switch (ccMaskRule) {

case "EQ": return (field == "EQ");

case "NE": return (field != "EQ");

case "LT": return (field == "LT");

case "GE": return (field == "GT" || field == "EQ");

case "LE": return (field == "LT" || field == "EQ");

case "GT": return (field == "GT");

case "TR": return TRUE;

case "FL": return FALSE;

case "": return TRUE;

}

}

enum GenerateCC(float value) {

if (value == NaN) {

return UN;

} else if (value < 0) {

return LT;

} else if (value == 0) {

return EQ;

} else {

return GT;

}

}

void UpdateDestination(floatVec destination, floatVec result)

{

floatVec merged;

ccVec mergedCC;

// Merge the converted result into the destination register, under

// control of the compile- and run-time write masks.

merged = destination;

mergedCC = cc;

if (instrMask.x && TestCC(cc.c***)) {

merged.x = result.x;

if (updatecc) mergedCC.x = GenerateCC(result.x);

}

if (instrMask.y && TestCC(cc.*c**)) {

merged.y = result.y;

if (updatecc) mergedCC.y = GenerateCC(result.y);

}

if (instrMask.z && TestCC(cc.**c*)) {

merged.z = result.z;

if (updatecc) mergedCC.z = GenerateCC(result.z);

}

if (instrMask.w && TestCC(cc.***c)) {

merged.w = result.w;

if (updatecc) mergedCC.w = GenerateCC(result.w);

}

// Write out the new destination register and condition code.

destination = merged;

cc = mergedCC;

}

Section 2.14.2.3, Vertex Program Execution

In the VP1 execution environment, vertex programs consist of a sequence of

instructions without no support for branching. Vertex programs begin by

executing the first instruction in the program, and execute instructions

in the order specified in the program until the last instruction is

reached.

VP2 vertex programs can contain one or more instruction labels, matching

the grammar rule <vp2-instructionLabel>. An instruction label can be

referred to explicitly in branch (BRA) or subroutine call (CAL)

instructions. Instruction labels can be defined or used at any point in

the body of a program, and can be used in instructions before being

defined in the program string.

VP2 vertex program branching instructions can be conditional. The branch

condition is specified by the <vp2-conditionMask> and may depend on the

contents of the condition code register. Branch conditions are evaluated

by evaluating a condition code write mask in exactly the same manner as

done for register writes (section 2.14.2.2). If any of the four

components of the condition code write mask are enabled, the branch is

taken and execution continues with the instruction following the label

specified in the instruction. Otherwise, the instruction is ignored and

vertex program execution continues with the next instruction. In the

following example code,

MOVC CC, c[0]; # c[0]=(-2, 0, 2, NaN), CC gets (LT,EQ,GT,UN)

BRA label1 (LT.xyzw);

MOV R0,R1; # not executed

label1:

BRA label2 (LT.wyzw);

MOV R0,R2; # executed

label2:

the first BRA instruction loads a condition code of (LT,EQ,GT,UN) while

the second BRA instruction loads a condition code of (UN,EQ,GT,UN). The

first branch will be taken because the "x" component evaluates to LT; the

second branch will not be taken because no component evaluates to LT.

VP2 vertex programs can specify subroutine calls. When a subroutine call

(CAL) instruction is executed, a reference to the instruction immediately

following the CAL instruction is pushed onto the call stack. When a

subroutine return (RET) instruction is executed, an instruction reference

is popped off the call stack and program execution continues with the

popped instruction. A vertex program will terminate if a CAL instruction

is executed with four entries already in the call stack or if a RET

instruction is executed with an empty call stack.

If a VP2 vertex program has an instruction label "main", program execution

begins with the instruction immediately following the instruction label.

Otherwise, program execution begins with the first instruction of the

program. Instructions will be executed sequentially in the order

specified in the program, although branch instructions will affect the

instruction execution order, as described above. A vertex program will

terminate after executing a RET instruction with an empty call stack. A

vertex program will also terminate after executing the last instruction in

the program, unless that instruction was a taken branch.

A vertex program will fail to load if an instruction refers to a label

that is not defined in the program string.

A vertex program will terminate abnormally if a subroutine call

instruction produces a call stack overflow. Additionally, a vertex

program will terminate abnormally after executing 65536 instructions to

prevent hangs caused by infinite loops in the program.

When a vertex program terminates, normally or abnormally, it will emit a

vertex whose attributes are taken from the final values of the vertex

result registers (section 2.14.1.5).

Section 2.14.3, Vertex Program Instruction Set

The following sections describe the set of supported vertex program

instructions. Instructions available only in the VP1.1 or VP2 execution

environment will be noted in the instruction description.

Each section will contain pseudocode describing the instruction.

Instructions will have up to three operands, referred to as "op0", "op1",

and "op2". The operands are loaded using the mechanisms specified in

section 2.14.2.1. Most instructions will generate a result vector called

"result". The result vector is then written to the destination register

specified in the instruction using the mechanisms specified in section

2.14.2.2.

Operands and results are represented as 32-bit single-precision

floating-point numbers according to the IEEE 754 floating-point

specification. IEEE denorm encodings, used to represent numbers smaller

than 2^-126, are not supported. All such numbers are flushed to zero.

There are three special encodings referred to in this section: +INF means

"positive infinity", -INF means "negative infinity", and NaN refers to

"not a number".

Arithmetic operations are typically carried out in single precision

according to the rules specified in the IEEE 754 specification. Any

exceptions and special cases will be noted in the instruction description.

Section 2.14.3.1, ABS: Absolute Value

The ABS instruction performs a component-wise absolute value operation on

the single operand to yield a result vector.

tmp = VectorLoad(op0);

result.x = abs(tmp.x);

result.y = abs(tmp.y);

result.z = abs(tmp.z);

result.w = abs(tmp.w);

The following special-case rules apply to absolute value operation:

1. abs(NaN) = NaN.

2. abs(-INF) = abs(+INF) = +INF.

3. abs(-0.0) = abs(+0.0) = +0.0.

The ABS instruction is available only in the VP1.1 and VP2 execution

environments.

In the VP1.0 execution environment, the same functionality can be achieved

with "MAX result, src, -src".

In the VP2 execution environment, the ABS instruction is effectively

obsolete, since instructions can take the absolute value of each operand

at no cost.

Section 2.14.3.2, ADD: Add

The ADD instruction performs a component-wise add of the two operands to

yield a result vector.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = tmp0.x + tmp1.x;

result.y = tmp0.y + tmp1.y;

result.z = tmp0.z + tmp1.z;

result.w = tmp0.w + tmp1.w;

The following special-case rules apply to addition:

1. "A+B" is always equivalent to "B+A".

2. NaN + <x> = NaN, for all <x>.

3. +INF + <x> = +INF, for all <x> except NaN and -INF.

4. -INF + <x> = -INF, for all <x> except NaN and +INF.

5. +INF + -INF = NaN.

6. -0.0 + <x> = <x>, for all <x>.

7. +0.0 + <x> = <x>, for all <x> except -0.0.

Section 2.14.3.3, ARA: Address Register Add

The ARA instruction adds two pairs of components of a vector address

register operand to produce an integer result vector. The "x" and "z"

components of the result vector contain the sum of the "x" and "z"

components of the operand; the "y" and "w" components of the result vector

contain the sum of the "y" and "w" components of the operand. Each

component of the result vector is clamped to [-512, +511], the range of

representable address register components.

itmp = AddrVectorLoad(op0);

iresult.x = itmp.x + itmp.z;

iresult.y = itmp.y + itmp.w;

iresult.z = itmp.x + itmp.z;

iresult.w = itmp.y + itmp.w;

if (iresult.x < -512) iresult.x = -512;

if (iresult.x > 511) iresult.x = 511;

if (iresult.y < -512) iresult.y = -512;

if (iresult.y > 511) iresult.y = 511;

if (iresult.z < -512) iresult.z = -512;

if (iresult.z > 511) iresult.z = 511;

if (iresult.w < -512) iresult.w = -512;

if (iresult.w > 511) iresult.w = 511;

Component swizzling is not supported when the operand is loaded.

The ARA instruction is available only in the VP2 execution environment.

Section 2.14.3.4, ARL: Address Register Load

In the VP1 execution environment, the ARL instruction loads a single

scalar operand and performs a floor operation to generate an integer

scalar to be written to the address register.

tmp = ScalarLoad(op0);

iresult.x = floor(tmp);

In the VP2 execution environment, the ARL instruction loads a single

vector operand and performs a component-wise floor operation to generate

an integer result vector. Each component of the result vector is clamped

to [-512, +511], the range of representable address register components.

The ARL instruction applies all masking operations to address register

writes as are described in section 2.14.2.2.

tmp = VectorLoad(op0);

iresult.x = floor(tmp.x);

iresult.y = floor(tmp.y);

iresult.z = floor(tmp.z);

iresult.w = floor(tmp.w);

if (iresult.x < -512) iresult.x = -512;

if (iresult.x > 511) iresult.x = 511;

if (iresult.y < -512) iresult.y = -512;

if (iresult.y > 511) iresult.y = 511;

if (iresult.z < -512) iresult.z = -512;

if (iresult.z > 511) iresult.z = 511;

if (iresult.w < -512) iresult.w = -512;

if (iresult.w > 511) iresult.w = 511;

The following special-case rules apply to floor computation:

1. floor(NaN) = NaN.

2. floor(<x>) = <x>, for -0.0, +0.0, -INF, and +INF. In all cases, the

sign of the result is equal to the sign of the operand.

Section 2.14.3.5, ARR: Address Register Load (with round)

The ARR instruction loads a single vector operand and performs a

component-wise round operation to generate an integer result vector. Each

component of the result vector is clamped to [-512, +511], the range of

representable address register components. The ARR instruction applies

all masking operations to address register writes as described in section

2.14.2.2.

tmp = VectorLoad(op0);

iresult.x = round(tmp.x);

iresult.y = round(tmp.y);

iresult.z = round(tmp.z);

iresult.w = round(tmp.w);

if (iresult.x < -512) iresult.x = -512;

if (iresult.x > 511) iresult.x = 511;

if (iresult.y < -512) iresult.y = -512;

if (iresult.y > 511) iresult.y = 511;

if (iresult.z < -512) iresult.z = -512;

if (iresult.z > 511) iresult.z = 511;

if (iresult.w < -512) iresult.w = -512;

if (iresult.w > 511) iresult.w = 511;

The rounding function, round(x), returns the nearest integer to <x>. If

the fractional portion of <x> is 0.5, round(x) selects the nearest even

integer.

The ARR instruction is available only in the VP2 execution environment.

Section 2.14.3.6, BRA: Branch

The BRA instruction conditionally transfers control to the instruction

following the label specified in the instruction. The following

pseudocode describes the operation of the instruction:

if (TestCC(cc.c***) || TestCC(cc.*c**) ||

TestCC(cc.**c*) || TestCC(cc.***c)) {

// continue execution at instruction following <branchLabel>

} else {

// do nothing

}

In the pseudocode, <branchLabel> is the label specified in the instruction

matching the <vp2-branchLabel> grammar rule.

The BRA instruction is available only in the VP2 execution environment.

Section 2.14.3.7, CAL: Subroutine Call

The CAL instruction conditionally transfers control to the instruction

following the label specified in the instruction. It also pushes a

reference to the instruction immediately following the CAL instruction

onto the call stack, where execution will continue after executing the

matching RET instruction. The following pseudocode describes the

operation of the instruction:

if (TestCC(cc.c***) || TestCC(cc.*c**) ||

TestCC(cc.**c*) || TestCC(cc.***c)) {

if (callStackDepth >= 4) {

// terminate vertex program

} else {

callStack[callStackDepth] = nextInstruction;

callStackDepth++;

}

// continue execution at instruction following <branchLabel>

} else {

// do nothing

}

In the pseudocode, <branchLabel> is the label specified in the instruction

matching the <vp2-branchLabel> grammar rule, <callStackDepth> is the

current depth of the call stack, <callStack> is an array holding the call

stack, and <nextInstruction> is a reference to the instruction immediately

following the present one in the program string.

The CAL instruction is available only in the VP2 execution environment.

Section 2.14.3.8, COS: Cosine

The COS instruction approximates the cosine of the angle specified by the

scalar operand and replicates the approximation to all four components of

the result vector. The angle is specified in radians and does not have to

be in the range [0,2*PI].

tmp = ScalarLoad(op0);

result.x = ApproxCosine(tmp);

result.y = ApproxCosine(tmp);

result.z = ApproxCosine(tmp);

result.w = ApproxCosine(tmp);

The approximation function ApproxCosine is accurate to at least 22 bits

with an angle in the range [0,2*PI].

| ApproxCosine(x) - cos(x) | < 1.0 / 2^22, if 0.0 <= x < 2.0 * PI.

The error in the approximation will typically increase with the absolute

value of the angle when the angle falls outside the range [0,2*PI].

The following special-case rules apply to cosine approximation:

1. ApproxCosine(NaN) = NaN.

2. ApproxCosine(+/-INF) = NaN.

3. ApproxCosine(+/-0.0) = +1.0.

The COS instruction is available only in the VP2 execution environment.

Section 2.14.3.9, DP3: 3-component Dot Product

The DP3 instruction computes a three component dot product of the two

operands (using the x, y, and z components) and replicates the dot product

to all four components of the result vector.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1):

result.x = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z);

result.y = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z);

result.z = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z);

result.w = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z);

Section 2.14.3.10, DP4: 4-component Dot Product

The DP4 instruction computes a four component dot product of the two

operands and replicates the dot product to all four components of the

result vector.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1):

result.x = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z) + (tmp0.w * tmp1.w);

result.y = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z) + (tmp0.w * tmp1.w);

result.z = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z) + (tmp0.w * tmp1.w);

result.w = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z) + (tmp0.w * tmp1.w);

Section 2.14.3.11, DPH: Homogeneous Dot Product

The DPH instruction computes a four-component dot product of the two

operands, except that the W component of the first operand is assumed to

be 1.0. The instruction replicates the dot product to all four components

of the result vector.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1):

result.x = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z) + tmp1.w;

result.y = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z) + tmp1.w;

result.z = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z) + tmp1.w;

result.w = (tmp0.x * tmp1.x) + (tmp0.y * tmp1.y) +

(tmp0.z * tmp1.z) + tmp1.w;

The DPH instruction is available only in the VP1.1 and VP2 execution

environments.

Section 2.14.3.12, DST: Distance Vector

The DST instruction computes a distance vector from two specially-

formatted operands. The first operand should be of the form [NA, d^2,

d^2, NA] and the second operand should be of the form [NA, 1/d, NA, 1/d],

where NA values are not relevant to the calculation and d is a vector

length. If both vectors satisfy these conditions, the result vector will

be of the form [1.0, d, d^2, 1/d].

The exact behavior is specified in the following pseudo-code:

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = 1.0;

result.y = tmp0.y * tmp1.y;

result.z = tmp0.z;

result.w = tmp1.w;

Given an arbitrary vector, d^2 can be obtained using the DP3 instruction

(using the same vector for both operands) and 1/d can be obtained from d^2

using the RSQ instruction.

This distance vector is useful for per-vertex light attenuation

calculations: a DP3 operation using the distance vector and an

attenuation constants vector as operands will yield the attenuation

factor.

Section 2.14.3.13, EX2: Exponential Base 2

The EX2 instruction approximates 2 raised to the power of the scalar

operand and replicates it to all four components of the result vector.

tmp = ScalarLoad(op0);

result.x = Approx2ToX(tmp);

result.y = Approx2ToX(tmp);

result.z = Approx2ToX(tmp);

result.w = Approx2ToX(tmp);

The approximation function is accurate to at least 22 bits:

| Approx2ToX(x) - 2^x | < 1.0 / 2^22, if 0.0 <= x < 1.0,

and, in general,

| Approx2ToX(x) - 2^x | < (1.0 / 2^22) * (2^floor(x)).

The following special-case rules apply to exponential approximation:

1. Approx2ToX(NaN) = NaN.

2. Approx2ToX(-INF) = +0.0.

3. Approx2ToX(+INF) = +INF.

4. Approx2ToX(+/-0.0) = +1.0.

The EX2 instruction is available only in the VP2 execution environment.

Section 2.14.3.14, EXP: Exponential Base 2 (approximate)

The EXP instruction computes a rough approximation of 2 raised to the

power of the scalar operand. The approximation is returned in the "z"

component of the result vector. A vertex program can also use the "x" and

"y" components of the result vector to generate a more accurate

approximation by evaluating

result.x * f(result.y),

where f(x) is a user-defined function that approximates 2^x over the

domain [0.0, 1.0). The "w" component of the result vector is always 1.0.

The exact behavior is specified in the following pseudo-code:

tmp = ScalarLoad(op0);

result.x = 2^floor(tmp);

result.y = tmp - floor(tmp);

result.z = RoughApprox2ToX(tmp);

result.w = 1.0;

The approximation function is accurate to at least 11 bits:

| RoughApprox2ToX(x) - 2^x | < 1.0 / 2^11, if 0.0 <= x < 1.0,

and, in general,

| RoughApprox2ToX(x) - 2^x | < (1.0 / 2^11) * (2^floor(x)).

The following special cases apply to the EXP instruction:

1. RoughApprox2ToX(NaN) = NaN.

2. RoughApprox2ToX(-INF) = +0.0.

3. RoughApprox2ToX(+INF) = +INF.

4. RoughApprox2ToX(+/-0.0) = +1.0.

The EXP instruction is present for compatibility with the original

NV_vertex_program instruction set; it is recommended that applications

using NV_vertex_program2 use the EX2 instruction instead.

Section 2.14.3.15, FLR: Floor

The FLR instruction performs a component-wise floor operation on the

operand to generate a result vector. The floor of a value is defined as

the largest integer less than or equal to the value. The floor of 2.3 is

2.0; the floor of -3.6 is -4.0.

tmp = VectorLoad(op0);

result.x = floor(tmp.x);

result.y = floor(tmp.y);

result.z = floor(tmp.z);

result.w = floor(tmp.w);

The following special-case rules apply to floor computation:

1. floor(NaN) = NaN.

2. floor(<x>) = <x>, for -0.0, +0.0, -INF, and +INF. In all cases, the

sign of the result is equal to the sign of the operand.

The FLR instruction is available only in the VP2 execution environment.

Section 2.14.3.16, FRC: Fraction

The FRC instruction extracts the fractional portion of each component of

the operand to generate a result vector. The fractional portion of a

component is defined as the result after subtracting off the floor of the

component (see FLR), and is always in the range [0.00, 1.00).

For negative values, the fractional portion is NOT the number written to

the right of the decimal point -- the fractional portion of -1.7 is not

0.7 -- it is 0.3. 0.3 is produced by subtracting the floor of -1.7 (-2.0)

from -1.7.

tmp = VectorLoad(op0);

result.x = tmp.x - floor(tmp.x);

result.y = tmp.y - floor(tmp.y);

result.z = tmp.z - floor(tmp.z);

result.w = tmp.w - floor(tmp.w);

The following special-case rules, which can be derived from the rules for

FLR and ADD apply to fraction computation:

1. fraction(NaN) = NaN.

2. fraction(+/-INF) = NaN.

3. fraction(+/-0.0) = +0.0.

The FRC instruction is available only in the VP2 execution environment.

Section 2.14.3.17, LG2: Logarithm Base 2

The LG2 instruction approximates the base 2 logarithm of the scalar

operand and replicates it to all four components of the result vector.

tmp = ScalarLoad(op0);

result.x = ApproxLog2(tmp);

result.y = ApproxLog2(tmp);

result.z = ApproxLog2(tmp);

result.w = ApproxLog2(tmp);

The approximation function is accurate to at least 22 bits:

| ApproxLog2(x) - log_2(x) | < 1.0 / 2^22.

Note that for large values of x, there are not enough bits in the

floating-point storage format to represent a result that precisely.

The following special-case rules apply to logarithm approximation:

1. ApproxLog2(NaN) = NaN.

2. ApproxLog2(+INF) = +INF.

3. ApproxLog2(+/-0.0) = -INF.

4. ApproxLog2(x) = NaN, -INF < x < -0.0.

5. ApproxLog2(-INF) = NaN.

The LG2 instruction is available only in the VP2 execution environment.

Section 2.14.3.18, LIT: Compute Light Coefficients

The LIT instruction accelerates per-vertex lighting by computing lighting

coefficients for ambient, diffuse, and specular light contributions. The

"x" component of the operand is assumed to hold a diffuse dot product (n

dot VP_pli, as in the vertex lighting equations in Section 2.13.1). The

"y" component of the operand is assumed to hold a specular dot product (n

dot h_i). The "w" component of the operand is assumed to hold the

specular exponent of the material (s_rm), and is clamped to the range

(-128, +128) exclusive.

The "x" component of the result vector receives the value that should be

multiplied by the ambient light/material product (always 1.0). The "y"

component of the result vector receives the value that should be

multiplied by the diffuse light/material product (n dot VP_pli). The "z"

component of the result vector receives the value that should be

multiplied by the specular light/material product (f_i * (n dot h_i) ^

s_rm). The "w" component of the result is the constant 1.0.

Negative diffuse and specular dot products are clamped to 0.0, as is done

in the standard per-vertex lighting operations. In addition, if the

diffuse dot product is zero or negative, the specular coefficient is

forced to zero.

tmp = VectorLoad(op0);

if (t.x < 0) t.x = 0;

if (t.y < 0) t.y = 0;

if (t.w < -(128.0-epsilon)) t.w = -(128.0-epsilon);

else if (t.w > 128-epsilon) t.w = 128-epsilon;

result.x = 1.0;

result.y = t.x;

result.z = (t.x > 0) ? RoughApproxPower(t.y, t.w) : 0.0;

result.w = 1.0;

The exponentiation approximation function is defined in terms of the base

2 exponentiation and logarithm approximation operations in the EXP and LOG

instructions, including errors and the processing of any special cases.

In particular,

RoughApproxPower(a,b) = RoughApproxExp2(b * RoughApproxLog2(a)).

The following special-case rules, which can be derived from the rules in

the LOG, MUL, and EXP instructions, apply to exponentiation:

1. RoughApproxPower(NaN, <x>) = NaN,

2. RoughApproxPower(<x>, <y>) = NaN, if x <= -0.0,

3. RoughApproxPower(+/-0.0, <x>) = +0.0, if x > +0.0, or

+INF, if x < -0.0,

4. RoughApproxPower(+1.0, <x>) = +1.0, if x is not NaN,

5. RoughApproxPower(+INF, <x>) = +INF, if x > +0.0, or

+0.0, if x < -0.0,

6. RoughApproxPower(<x>, +/-0.0) = +1.0, if x >= -0.0

7. RoughApproxPower(<x>, +INF) = +0.0, if -0.0 <= x < +1.0,

+INF, if x > +1.0,

8. RoughApproxPower(<x>, +INF) = +INF, if -0.0 <= x < +1.0,

+0.0, if x > +1.0,

9. RoughApproxPower(<x>, +1.0) = <x>, if x >= +0.0, and

10. RoughApproxPower(<x>, NaN) = NaN.

Section 2.14.3.19, LOG: Logarithm Base 2 (Approximate)

The LOG instruction computes a rough approximation of the base 2 logarithm

of the absolute value of the scalar operand. The approximation is

returned in the "z" component of the result vector. A vertex program can

also use the "x" and "y" components of the result vector to generate a

more accurate approximation by evaluating

result.x + f(result.y),

where f(x) is a user-defined function that approximates 2^x over the

domain [1.0, 2.0). The "w" component of the result vector is always 1.0.

The exact behavior is specified in the following pseudo-code:

tmp = fabs(ScalarLoad(op0));

result.x = floor(log2(tmp));

result.y = tmp / (2^floor(log2(tmp)));

result.z = RoughApproxLog2(tmp);

result.w = 1.0;

The approximation function is accurate to at least 11 bits:

| RoughApproxLog2(x) - log_2(x) | < 1.0 / 2^11.

The following special-case rules apply to the LOG instruction:

1. RoughApproxLog2(NaN) = NaN.

2. RoughApproxLog2(+INF) = +INF.

3. RoughApproxLog2(+0.0) = -INF.

The LOG instruction is present for compatibility with the original

NV_vertex_program instruction set; it is recommended that applications

using NV_vertex_program2 use the LG2 instruction instead.

Section 2.14.3.20, MAD: Multiply And Add

The MAD instruction performs a component-wise multiply of the first two

operands, and then does a component-wise add of the product to the third

operand to yield a result vector.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

tmp2 = VectorLoad(op2);

result.x = tmp0.x * tmp1.x + tmp2.x;

result.y = tmp0.y * tmp1.y + tmp2.y;

result.z = tmp0.z * tmp1.z + tmp2.z;

result.w = tmp0.w * tmp1.w + tmp2.w;

All special case rules applicable to the ADD and MUL instructions apply to

the individual components of the MAD operation as well.

Section 2.14.3.21, MAX: Maximum

The MAX instruction computes component-wise maximums of the values in the

two operands to yield a result vector.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = max(tmp0.x, tmp1.x);

result.y = max(tmp0.y, tmp1.y);

result.z = max(tmp0.z, tmp1.z);

result.w = max(tmp0.w, tmp1.w);

The following special cases apply to the maximum operation:

1. max(A,B) is always equivalent to max(B,A).

2. max(NaN, <x>) == NaN, for all <x>.

Section 2.14.3.22, MIN: Minimum

The MIN instruction computes component-wise minimums of the values in the

two operands to yield a result vector.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = min(tmp0.x, tmp1.x);

result.y = min(tmp0.y, tmp1.y);

result.z = min(tmp0.z, tmp1.z);

result.w = min(tmp0.w, tmp1.w);

The following special cases apply to the minimum operation:

1. min(A,B) is always equivalent to min(B,A).

2. min(NaN, <x>) == NaN, for all <x>.

Section 2.14.3.23, MOV: Move

The MOV instruction copies the value of the operand to yield a result

vector.

result = VectorLoad(op0);

Section 2.14.3.24, MUL: Multiply

The MUL instruction performs a component-wise multiply of the two operands

to yield a result vector.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = tmp0.x * tmp1.x;

result.y = tmp0.y * tmp1.y;

result.z = tmp0.z * tmp1.z;

result.w = tmp0.w * tmp1.w;

The following special-case rules apply to multiplication:

1. "A*B" is always equivalent to "B*A".

2. NaN * <x> = NaN, for all <x>.

3. +/-0.0 * +/-INF = NaN.

4. +/-0.0 * <x> = +/-0.0, for all <x> except -INF, +INF, and NaN. The

sign of the result is positive if the signs of the two operands match

and negative otherwise.

5. +/-INF * <x> = +/-INF, for all <x> except -0.0, +0.0, and NaN. The

sign of the result is positive if the signs of the two operands match

and negative otherwise.

6. +1.0 * <x> = <x>, for all <x>.

Section 2.14.3.25, RCC: Reciprocal (Clamped)

The RCC instruction approximates the reciprocal of the scalar operand,

clamps the result to one of two ranges, and replicates the clamped result

to all four components of the result vector.

If the approximate reciprocal is greater than 0.0, the result is clamped

to the range [2^-64, 2^+64]. If the approximate reciprocal is not greater

than zero, the result is clamped to the range [-2^+64, -2^-64].

tmp = ScalarLoad(op0);

result.x = ClampApproxReciprocal(tmp);

result.y = ClampApproxReciprocal(tmp);

result.z = ClampApproxReciprocal(tmp);

result.w = ClampApproxReciprocal(tmp);

The approximation function is accurate to at least 22 bits:

| ClampApproxReciprocal(x) - (1/x) | < 1.0 / 2^22, if 1.0 <= x < 2.0.

The following special-case rules apply to reciprocation:

1. ClampApproxReciprocal(NaN) = NaN.

2. ClampApproxReciprocal(+INF) = +2^-64.

3. ClampApproxReciprocal(-INF) = -2^-64.

4. ClampApproxReciprocal(+0.0) = +2^64.

5. ClampApproxReciprocal(-0.0) = -2^64.

6. ClampApproxReciprocal(x) = +2^-64, if -2^64 < x < +INF.

7. ClampApproxReciprocal(x) = -2^-64, if -INF < x < -2^-64.

8. ClampApproxReciprocal(x) = +2^64, if +0.0 < x < +2^-64.

9. ClampApproxReciprocal(x) = -2^64, if -2^-64 < x < -0.0.

The RCC instruction is available only in the VP1.1 and VP2 execution

environments.

Section 2.14.3.26, RCP: Reciprocal

The RCP instruction approximates the reciprocal of the scalar operand and

replicates it to all four components of the result vector.

tmp = ScalarLoad(op0);

result.x = ApproxReciprocal(tmp);

result.y = ApproxReciprocal(tmp);

result.z = ApproxReciprocal(tmp);

result.w = ApproxReciprocal(tmp);

The approximation function is accurate to at least 22 bits:

| ApproxReciprocal(x) - (1/x) | < 1.0 / 2^22, if 1.0 <= x < 2.0.

The following special-case rules apply to reciprocation:

1. ApproxReciprocal(NaN) = NaN.

2. ApproxReciprocal(+INF) = +0.0.

3. ApproxReciprocal(-INF) = -0.0.

4. ApproxReciprocal(+0.0) = +INF.

5. ApproxReciprocal(-0.0) = -INF.

Section 2.14.3.27, RET: Subroutine Call Return

The RET instruction conditionally returns from a subroutine initiated by a

CAL instruction by popping an instruction reference off the top of the

call stack and transferring control to the referenced instruction. The

following pseudocode describes the operation of the instruction:

if (TestCC(cc.c***) || TestCC(cc.*c**) ||

TestCC(cc.**c*) || TestCC(cc.***c)) {

if (callStackDepth <= 0) {

// terminate vertex program

} else {

callStackDepth--;

instruction = callStack[callStackDepth];

}

// continue execution at <instruction>

} else {

// do nothing

}

In the pseudocode, <callStackDepth> is the depth of the call stack,

<callStack> is an array holding the call stack, and <instruction> is a

reference to an instruction previously pushed onto the call stack.

The RET instruction is available only in the VP2 execution environment.

Section 2.14.3.28, RSQ: Reciprocal Square Root

The RSQ instruction approximates the reciprocal of the square root of the

scalar operand and replicates it to all four components of the result

vector.

tmp = ScalarLoad(op0);

result.x = ApproxRSQRT(tmp);

result.y = ApproxRSQRT(tmp);

result.z = ApproxRSQRT(tmp);

result.w = ApproxRSQRT(tmp);

The approximation function is accurate to at least 22 bits:

| ApproxRSQRT(x) - (1/x) | < 1.0 / 2^22, if 1.0 <= x < 4.0.

The following special-case rules apply to reciprocal square roots:

1. ApproxRSQRT(NaN) = NaN.

2. ApproxRSQRT(+INF) = +0.0.

3. ApproxRSQRT(-INF) = NaN.

4. ApproxRSQRT(+0.0) = +INF.

5. ApproxRSQRT(-0.0) = -INF.

6. ApproxRSQRT(x) = NaN, if -INF < x < -0.0.

Section 2.14.3.29, SEQ: Set on Equal

The SEQ instruction performs a component-wise comparison of the two

operands. Each component of the result vector is 1.0 if the corresponding

component of the first operand is equal to that of the second, and 0.0

otherwise.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = (tmp0.x == tmp1.x) ? 1.0 : 0.0;

result.y = (tmp0.y == tmp1.y) ? 1.0 : 0.0;

result.z = (tmp0.z == tmp1.z) ? 1.0 : 0.0;

result.w = (tmp0.w == tmp1.w) ? 1.0 : 0.0;

if (tmp0.x is NaN or tmp1.x is NaN) result.x = NaN;

if (tmp0.y is NaN or tmp1.y is NaN) result.y = NaN;

if (tmp0.z is NaN or tmp1.z is NaN) result.z = NaN;

if (tmp0.w is NaN or tmp1.w is NaN) result.w = NaN;

The following special-case rules apply to SEQ:

1. (<x> == <y>) and (<y> == <x>) always produce the same result.

1. (NaN == <x>) is FALSE for all <x>, including NaN.

2. (+INF == +INF) and (-INF == -INF) are TRUE.

3. (-0.0 == +0.0) and (+0.0 == -0.0) are TRUE.

The SEQ instruction is available only in the VP2 execution environment.

Section 2.14.3.30, SFL: Set on False

The SFL instruction is a degenerate case of the other "Set on"

instructions that sets all components of the result vector to

0.0.

result.x = 0.0;

result.y = 0.0;

result.z = 0.0;

result.w = 0.0;

The SFL instruction is available only in the VP2 execution environment.

Section 2.14.3.31, SGE: Set on Greater Than or Equal

The SGE instruction performs a component-wise comparison of the two

operands. Each component of the result vector is 1.0 if the corresponding

component of the first operands is greater than or equal that of the

second, and 0.0 otherwise.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = (tmp0.x >= tmp1.x) ? 1.0 : 0.0;

result.y = (tmp0.y >= tmp1.y) ? 1.0 : 0.0;

result.z = (tmp0.z >= tmp1.z) ? 1.0 : 0.0;

result.w = (tmp0.w >= tmp1.w) ? 1.0 : 0.0;

if (tmp0.x is NaN or tmp1.x is NaN) result.x = NaN;

if (tmp0.y is NaN or tmp1.y is NaN) result.y = NaN;

if (tmp0.z is NaN or tmp1.z is NaN) result.z = NaN;

if (tmp0.w is NaN or tmp1.w is NaN) result.w = NaN;

The following special-case rules apply to SGE:

1. (NaN >= <x>) and (<x> >= NaN) are FALSE for all <x>.

2. (+INF >= +INF) and (-INF >= -INF) are TRUE.

3. (-0.0 >= +0.0) and (+0.0 >= -0.0) are TRUE.

Section 2.14.3.32, SGT: Set on Greater Than

The SGT instruction performs a component-wise comparison of the two

operands. Each component of the result vector is 1.0 if the corresponding

component of the first operands is greater than that of the second, and

0.0 otherwise.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = (tmp0.x > tmp1.x) ? 1.0 : 0.0;

result.y = (tmp0.y > tmp1.y) ? 1.0 : 0.0;

result.z = (tmp0.z > tmp1.z) ? 1.0 : 0.0;

result.w = (tmp0.w > tmp1.w) ? 1.0 : 0.0;

if (tmp0.x is NaN or tmp1.x is NaN) result.x = NaN;

if (tmp0.y is NaN or tmp1.y is NaN) result.y = NaN;

if (tmp0.z is NaN or tmp1.z is NaN) result.z = NaN;

if (tmp0.w is NaN or tmp1.w is NaN) result.w = NaN;

The following special-case rules apply to SGT:

1. (NaN > <x>) and (<x> > NaN) are FALSE for all <x>.

2. (-0.0 > +0.0) and (+0.0 > -0.0) are FALSE.

The SGT instruction is available only in the VP2 execution environment.

Section 2.14.3.33, SIN: Sine

The SIN instruction approximates the sine of the angle specified by the

scalar operand and replicates it to all four components of the result

vector. The angle is specified in radians and does not have to be in the

range [0,2*PI].

tmp = ScalarLoad(op0);

result.x = ApproxSine(tmp);

result.y = ApproxSine(tmp);

result.z = ApproxSine(tmp);

result.w = ApproxSine(tmp);

The approximation function is accurate to at least 22 bits with an angle

in the range [0,2*PI].

| ApproxSine(x) - sin(x) | < 1.0 / 2^22, if 0.0 <= x < 2.0 * PI.

The error in the approximation will typically increase with the absolute

value of the angle when the angle falls outside the range [0,2*PI].

The following special-case rules apply to cosine approximation:

1. ApproxSine(NaN) = NaN.

2. ApproxSine(+/-INF) = NaN.

3. ApproxSine(+/-0.0) = +/-0.0. The sign of the result is equal to the

sign of the single operand.

The SIN instruction is available only in the VP2 execution environment.

Section 2.14.3.34, SLE: Set on Less Than or Equal

The SLE instruction performs a component-wise comparison of the two

operands. Each component of the result vector is 1.0 if the corresponding

component of the first operand is less than or equal to that of the

second, and 0.0 otherwise.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = (tmp0.x <= tmp1.x) ? 1.0 : 0.0;

result.y = (tmp0.y <= tmp1.y) ? 1.0 : 0.0;

result.z = (tmp0.z <= tmp1.z) ? 1.0 : 0.0;

result.w = (tmp0.w <= tmp1.w) ? 1.0 : 0.0;

if (tmp0.x is NaN or tmp1.x is NaN) result.x = NaN;

if (tmp0.y is NaN or tmp1.y is NaN) result.y = NaN;

if (tmp0.z is NaN or tmp1.z is NaN) result.z = NaN;

if (tmp0.w is NaN or tmp1.w is NaN) result.w = NaN;

The following special-case rules apply to SLE:

1. (NaN <= <x>) and (<x> <= NaN) are FALSE for all <x>.

2. (+INF <= +INF) and (-INF <= -INF) are TRUE.

3. (-0.0 <= +0.0) and (+0.0 <= -0.0) are TRUE.

The SLE instruction is available only in the VP2 execution environment.

Section 2.14.3.35, SLT: Set on Less Than

The SLT instruction performs a component-wise comparison of the two

operands. Each component of the result vector is 1.0 if the corresponding

component of the first operand is less than that of the second, and 0.0

otherwise.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = (tmp0.x < tmp1.x) ? 1.0 : 0.0;

result.y = (tmp0.y < tmp1.y) ? 1.0 : 0.0;

result.z = (tmp0.z < tmp1.z) ? 1.0 : 0.0;

result.w = (tmp0.w < tmp1.w) ? 1.0 : 0.0;

if (tmp0.x is NaN or tmp1.x is NaN) result.x = NaN;

if (tmp0.y is NaN or tmp1.y is NaN) result.y = NaN;

if (tmp0.z is NaN or tmp1.z is NaN) result.z = NaN;

if (tmp0.w is NaN or tmp1.w is NaN) result.w = NaN;

The following special-case rules apply to SLT:

1. (NaN < <x>) and (<x> < NaN) are FALSE for all <x>.

2. (-0.0 < +0.0) and (+0.0 < -0.0) are FALSE.

Section 2.14.3.36, SNE: Set on Not Equal

The SNE instruction performs a component-wise comparison of the two

operands. Each component of the result vector is 1.0 if the corresponding

component of the first operand is not equal to that of the second, and 0.0

otherwise.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = (tmp0.x != tmp1.x) ? 1.0 : 0.0;

result.y = (tmp0.y != tmp1.y) ? 1.0 : 0.0;

result.z = (tmp0.z != tmp1.z) ? 1.0 : 0.0;

result.w = (tmp0.w != tmp1.w) ? 1.0 : 0.0;

if (tmp0.x is NaN or tmp1.x is NaN) result.x = NaN;

if (tmp0.y is NaN or tmp1.y is NaN) result.y = NaN;

if (tmp0.z is NaN or tmp1.z is NaN) result.z = NaN;

if (tmp0.w is NaN or tmp1.w is NaN) result.w = NaN;

The following special-case rules apply to SNE:

1. (<x> != <y>) and (<y> != <x>) always produce the same result.

2. (NaN != <x>) is TRUE for all <x>, including NaN.

3. (+INF != +INF) and (-INF != -INF) are FALSE.

4. (-0.0 != +0.0) and (+0.0 != -0.0) are TRUE.

The SNE instruction is available only in the VP2 execution environment.

Section 2.14.3.37, SSG: Set Sign

The SSG instruction generates a result vector containing the signs of each

component of the single operand. Each component of the result vector is

1.0 if the corresponding component of the operand is greater than zero,

0.0 if the corresponding component of the operand is equal to zero, and

-1.0 if the corresponding component of the operand is less than zero.

tmp = VectorLoad(op0);

result.x = SetSign(tmp.x);

result.y = SetSign(tmp.y);

result.z = SetSign(tmp.z);

result.w = SetSign(tmp.w);

The following special-case rules apply to SSG:

1. SetSign(NaN) = NaN.

2. SetSign(-0.0) = SetSign(+0.0) = 0.0.

3. SetSign(-INF) = -1.0.

4. SetSign(+INF) = +1.0.

5. SetSign(x) = -1.0, if -INF < x < -0.0.

6. SetSign(x) = +1.0, if +0.0 < x < +INF.

The SSG instruction is available only in the VP2 execution environment.

Section 2.14.3.38, STR: Set on True

The STR instruction is a degenerate case of the other "Set on"

instructions that sets all components of the result vector to 1.0.

result.x = 1.0;

result.y = 1.0;

result.z = 1.0;

result.w = 1.0;

The STR instruction is available only in the VP2 execution environment.

Section 2.14.3.39, SUB: Subtract

The SUB instruction performs a component-wise subtraction of the second

operand from the first to yield a result vector.

tmp0 = VectorLoad(op0);

tmp1 = VectorLoad(op1);

result.x = tmp0.x - tmp1.x;

result.y = tmp0.y - tmp1.y;

result.z = tmp0.z - tmp1.z;

result.w = tmp0.w - tmp1.w;

The SUB instruction is completely equivalent to an identical ADD

instruction in which the negate operator on the second operand is

reversed:

1. "SUB R0, R1, R2" is equivalent to "ADD R0, R1, -R2".

2. "SUB R0, R1, -R2" is equivalent to "ADD R0, R1, R2".

3. "SUB R0, R1, |R2|" is equivalent to "ADD R0, R1, -|R2|".

4. "SUB R0, R1, -|R2|" is equivalent to "ADD R0, R1, |R2|".

The SUB instruction is available only in the VP1.1 and VP2 execution

environments.

2.14.4 Vertex Arrays for Vertex Attributes

Data for vertex attributes in vertex program mode may be specified

using vertex array commands. The client may specify and enable any

of sixteen vertex attribute arrays.

The vertex attribute arrays are ignored when vertex program mode

is disabled. When vertex program mode is enabled, vertex attribute

arrays are used.

The command

void VertexAttribPointerNV(uint index, int size, enum type,

sizei stride, const void *pointer);

describes the locations and organizations of the sixteen vertex

attribute arrays. index specifies the particular vertex attribute

to be described. size indicates the number of values per vertex

that are stored in the array; size must be one of 1, 2, 3, or 4.

type specifies the data type of the values stored in the array.

type must be one of SHORT, FLOAT, DOUBLE, or UNSIGNED_BYTE and these

values correspond to the array types short, int, float, double, and

ubyte respectively. The INVALID_OPERATION error is generated if

type is UNSIGNED_BYTE and size is not 4. The INVALID_VALUE error

is generated if index is greater than 15. The INVALID_VALUE error

is generated if stride is negative.

The one, two, three, or four values in an array that correspond to a

single vertex attribute comprise an array element. The values within

each array element at stored sequentially in memory. If the stride

is specified as zero, then array elements are stored sequentially

as well. Otherwise points to the ith and (i+1)st elements of an array

differ by stride basic machine units (typically unsigned bytes),

the pointer to the (i+1)st element being greater. pointer specifies

the location in memory of the first value of the first element of

the array being specified.

Vertex attribute arrays are enabled with the EnableClientState command

and disabled with the DisableClientState command. The value of the

argument to either command is VERTEX_ATTRIB_ARRAYi_NV where i is an

integer between 0 and 15; specifying a value of i enables or

disables the vertex attribute array with index i. The constants

obey VERTEX_ATTRIB_ARRAYi_NV = VERTEX_ATTRIB_ARRAY0_NV + i.

When vertex program mode is enabled, the ArrayElement command operates

as described in this section in contrast to the behavior described

in section 2.8. Likewise, any vertex array transfer commands that

are defined in terms of ArrayElement (DrawArrays, DrawElements, and

DrawRangeElements) assume the operation of ArrayElement described

in this section when vertex program mode is enabled.

When vertex program mode is enabled, the ArrayElement command

transfers the ith element of particular enabled vertex arrays as

described below. For each enabled vertex attribute array, it is

as though the corresponding command from section 2.14.1.1 were

called with a pointer to element i. For each vertex attribute,

the corresponding command is VertexAttrib[size][type]v, where size

is one of [1,2,3,4], and type is one of [s,f,d,ub], corresponding

to the array types short, int, float, double, and ubyte respectively.

However, if a given vertex attribute array is disabled, but its

corresponding aliased conventional per-vertex parameter's vertex

array (as described in section 2.14.1.6) is enabled, then it is

as though the corresponding command from section 2.7 or section

2.6.2 were called with a pointer to element i. In this case, the

corresponding command is determined as described in section 2.8's

description of ArrayElement.

If the vertex attribute array 0 is enabled, it is as though

VertexAttrib[size][type]v(0, ...) is executed last, after the

executions of other corresponding commands. If the vertex attribute

array 0 is disabled but the vertex array is enabled, it is as though

Vertex[size][type]v is executed last, after the executions of other

corresponding commands.

2.14.5 Vertex State Programs

Vertex state programs share the same instruction set as and a similar

execution model to vertex programs. While vertex programs are executed

implicitly when a vertex transformation is provoked, vertex state programs

are executed explicitly, independently of any vertices. Vertex state

programs can write program parameter registers, but may not write vertex

result registers. Vertex state programs have not been extended beyond the

the VP1.0 execution environment, and are offered solely for compatibility

with that execution environment.

The purpose of a vertex state program is to update program parameter

registers by means of an application-defined program. Typically, an

application will load a set of program parameters and then execute a

vertex state program that reads and updates the program parameter

registers. For example, a vertex state program might normalize a set of

unnormalized vectors previously loaded as program parameters. The

expectation is that subsequently executed vertex programs would use the

normalized program parameters.

Vertex state programs are loaded with the same LoadProgramNV command (see

section 2.14.1.8) used to load vertex programs except that the target must

be VERTEX_STATE_PROGRAM_NV when loading a vertex state program.

Vertex state programs must conform to a more limited grammar than the

grammar for vertex programs. The vertex state program grammar for

syntactically valid sequences is the same as the grammar defined in

section 2.14.1.8 with the following modified rules:

<program> ::= <vp1-program>

<vp1-program> ::= "!!VSP1.0" <programBody> "END"

<dstReg> ::= <absProgParamReg>

| <temporaryReg>

<vertexAttribReg> ::= "v" "[" "0" "]"

A vertex state program fails to load if it does not write at least

one program parameter register.

A vertex state program fails to load if it contains more than 128

instructions.

A vertex state program fails to load if any instruction sources more

than one unique program parameter register.

A vertex state program fails to load if any instruction sources

more than one unique vertex attribute register (this is necessarily

true because only vertex attribute 0 is available in vertex state

programs).

The error INVALID_OPERATION is generated if a vertex state program

fails to load because it is not syntactically correct or for one

of the other reasons listed above.

A successfully loaded vertex state program is parsed into a sequence

of instructions. Each instruction is identified by its tokenized

name. The operation of these instructions when executed is defined

in section 2.14.1.10.

Executing vertex state programs is legal only outside a Begin/End

pair. A vertex state program may not read any vertex attribute

register other than register zero. A vertex state program may not

write any vertex result register.

The command

ExecuteProgramNV(enum target, uint id, const float *params);

executes the vertex state program named by id. The target must be

VERTEX_STATE_PROGRAM_NV and the id must be the name of program loaded

with a target type of VERTEX_STATE_PROGRAM_NV. params points to

an array of four floating-point values that are loaded into vertex

attribute register zero (the only vertex attribute readable from a

vertex state program).

The INVALID_OPERATION error is generated if the named program is

nonexistent, is invalid, or the program is not a vertex state

program. A vertex state program may not be valid for reasons

explained in section 2.14.5.

2.14.6, Program Options

In the VP1.1 and VP2.0 execution environment, vertex programs may specify

one or more program options that modify the execution environment,

according to the <option> grammar rule. The set of options available to

the program is described below.

Section 2.14.6.1, Position-Invariant Vertex Program Option

If <vp11-option> or <vp2-option> matches "NV_position_invariant", the

vertex program is presumed to be position-invariant. By default, vertex

programs are not position-invariant. Even if programs emulate the

conventional OpenGL transformation model, they may still not produce the

exact same transform results, due to rounding errors or different

operation orders. Such programs may not work well for multi-pass

rendering algorithms where the second and subsequent passes use an EQUAL

depth test.

Position-invariant vertex programs do not compute a final vertex position;

instead, the GL computes vertex coordinates as described in section 2.10.

This computation should produce exactly the same results as the

conventional OpenGL transformation model, assuming vertex weighting and

vertex blending are disabled.

A vertex program that specifies the position-invariant option will fail to

load if it writes to the HPOS result register.

Additionally, in the VP1.1 execution environment, position-invariant

programs can not use relative addressing for program parameters. Any

position-invariant VP1.1 program matches the grammar rule

<relProgParamReg>, will fail to load. No such restriction exists for

VP2.0 programs.

For position-invariant programs, the limit on the number of instructions

allowed in a program is reduced by four: position-invariant VP1.1 and

VP2.0 programs may have no more than 124 or 252 instructions,

respectively.

2.14.7 Tracking Matrices

As a convenience to applications, standard GL matrix state can be

tracked into program parameter vectors. This permits vertex programs

to access matrices specified through GL matrix commands.

In addition to GL's conventional matrices, several additional matrices

are available for tracking. These matrices have names of the form

MATRIXi_NV where i is between zero and n-1 where n is the value

of the MAX_TRACK_MATRICES_NV implementation dependent constant.

The MATRIXi_NV constants obey MATRIXi_NV = MATRIX0_NV + i. The value

of MAX_TRACK_MATRICES_NV must be at least eight. The maximum

stack depth for tracking matrices is defined by the

MAX_TRACK_MATRIX_STACK_DEPTH_NV and must be at least 1.

The command

TrackMatrixNV(enum target, uint address, enum matrix, enum transform);

tracks a given transformed version of a particular matrix into

a contiguous sequence of four vertex program parameter registers

beginning at address. target must be VERTEX_PROGRAM_NV (though

tracked matrices apply to vertex state programs as well because both

vertex state programs and vertex programs shared the same program

parameter registers). matrix must be one of NONE, MODELVIEW,

PROJECTION, TEXTURE, TEXTUREi_ARB (where i is between 0 and n-1

where n is the number of texture units supported), COLOR (if

the ARB_imaging subset is supported), MODELVIEW_PROJECTION_NV,

or MATRIXi_NV. transform must be one of IDENTITY_NV, INVERSE_NV,

TRANSPOSE_NV, or INVERSE_TRANSPOSE_NV. The INVALID_VALUE error is

generated if address is not a multiple of four.

The MODELVIEW_PROJECTION_NV matrix represents the concatenation of

the current modelview and projection matrices. If M is the current

modelview matrix and P is the current projection matrix, then the

MODELVIEW_PROJECTION_NV matrix is C and computed as

C = P M

Matrix tracking for the specified program parameter register and the

next consecutive three registers is disabled when NONE is supplied

for matrix. When tracking is disabled the previously tracked program

parameter registers retain the state of their last tracked values.

Otherwise, the specified transformed version of matrix is tracked into

the specified program parameter register and the next three registers.

Whenever the matrix changes, the transformed version of the matrix

is updated in the specified range of program parameter registers.

If TEXTURE is specified for matrix, the texture matrix for the current

active texture unit is tracked. If TEXTUREi_ARB is specified for

matrix, the <i>th texture matrix is tracked.

Matrices are tracked row-wise meaning that the top row of the

transformed matrix is loaded into the program parameter address,

the second from the top row of the transformed matrix is loaded into

the program parameter address+1, the third from the top row of the

transformed matrix is loaded into the program parameter address+2,

and the bottom row of the transformed matrix is loaded into the

program parameter address+3. The transformed matrix may be identical

to the specified matrix, the inverse of the specified matrix, the

transpose of the specified matrix, or the inverse transpose of the

specified matrix, depending on the value of transform.

When matrix tracking is enabled for a particular program parameter

register sequence, updates to the program parameter using

ProgramParameterNV commands, a vertex program, or a vertex state

program are not possible. The INVALID_OPERATION error is generated

if a ProgramParameterNV command is used to update a program parameter

register currently tracking a matrix.

The INVALID_OPERATION error is generated by ExecuteProgramNV when

the vertex state program requested for execution writes to a program

parameter register that is currently tracking a matrix because the

program is considered invalid.

2.14.8 Required Vertex Program State

The state required for vertex programs consists of:

a bit indicating whether or not program mode is enabled;

a bit indicating whether or not two-sided color mode is enabled;

a bit indicating whether or not program-specified point size mode

is enabled;

256 4-component floating-point program parameter registers;

16 4-component vertex attribute registers (though this state is

aliased with the current normal, primary color, secondary color,

fog coordinate, weights, and texture coordinate sets);

24 sets of matrix tracking state for each set of four sequential

program parameter registers, consisting of a n-valued integer

indicated the tracked matrix or GL_NONE (where n is 5 + the number

of texture units supported + the number of tracking matrices

supported) and a four-valued integer indicating the transformation

of the tracked matrix;

an unsigned integer naming the currently bound vertex program

and the state must be maintained to indicate which integers

are currently in use as program names.

Each existent program object consists of a target, a boolean indicating

whether the program is resident, an array of type ubyte containing the

program string, and the length of the program string array. Initially,

no program objects exist.

Program mode, two-sided color mode, and program-specified point size

mode are all initially disabled.

The initial state of all 256 program parameter registers is (0,0,0,0).

The initial state of the 16 vertex attribute registers is (0,0,0,1)

except in cases where a vertex attribute register aliases to a

conventional GL transform mode vertex parameter in which case

the initial state is the initial state of the respective aliased

conventional vertex parameter.

The initial state of the 24 sets of matrix tracking state is NONE

for the tracked matrix and IDENTITY_NV for the transformation of the

tracked matrix.

The initial currently bound program is zero.

The client state required to implement the 16 vertex attribute

arrays consists of 16 boolean values, 16 memory pointers, 16 integer

stride values, 16 symbolic constants representing array types,

and 16 integers representing values per element. Initially, the

boolean values are each disabled, the memory pointers are each null,

the strides are each zero, the array types are each FLOAT, and the

integers representing values per element are each four."

None.

None.

None.

None.

None.

None.

All relevant protocol is defined in the NV_vertex_program extension.

This list includes the errors specified in the NV_vertex_program

extension, modified as appropriate.

The error INVALID_VALUE is generated if VertexAttribNV is called where

index is greater than 15.

The error INVALID_VALUE is generated if any ProgramParameterNV has an

index is greater than 255 (was 95 in NV_vertex_program).

The error INVALID_VALUE is generated if VertexAttribPointerNV is called

where index is greater than 15.

The error INVALID_VALUE is generated if VertexAttribPointerNV is called

where size is not one of 1, 2, 3, or 4.

The error INVALID_VALUE is generated if VertexAttribPointerNV is called

where stride is negative.

The error INVALID_OPERATION is generated if VertexAttribPointerNV is

called where type is UNSIGNED_BYTE and size is not 4.

The error INVALID_VALUE is generated if LoadProgramNV is used to load a

program with an id of zero.

The error INVALID_OPERATION is generated if LoadProgramNV is used to load

an id that is currently loaded with a program of a different program

target.

The error INVALID_OPERATION is generated if the program passed to

LoadProgramNV fails to load because it is not syntactically correct based

on the specified target. The value of PROGRAM_ERROR_POSITION_NV is still

updated when this error is generated.

The error INVALID_OPERATION is generated if LoadProgramNV has a target of

VERTEX_PROGRAM_NV and the specified program fails to load because it does

not write the HPOS register at least once. The value of

PROGRAM_ERROR_POSITION_NV is still updated when this error is generated.

The error INVALID_OPERATION is generated if LoadProgramNV has a target of

VERTEX_STATE_PROGRAM_NV and the specified program fails to load because it

does not write at least one program parameter register. The value of

PROGRAM_ERROR_POSITION_NV is still updated when this error is generated.

The error INVALID_OPERATION is generated if the vertex program or vertex

state program passed to LoadProgramNV fails to load because it contains

more than 128 instructions (VP1 programs) or 256 instructions (VP2

programs). The value of PROGRAM_ERROR_POSITION_NV is still updated when

this error is generated.

The error INVALID_OPERATION is generated if a program is loaded with

LoadProgramNV for id when id is currently loaded with a program of a

different target.

The error INVALID_OPERATION is generated if BindProgramNV attempts to bind

to a program name that is not a vertex program (for example, if the

program is a vertex state program).

The error INVALID_VALUE is generated if GenProgramsNV is called where n is

negative.

The error INVALID_VALUE is generated if AreProgramsResidentNV is called

and any of the queried programs are zero or do not exist.

The error INVALID_OPERATION is generated if ExecuteProgramNV executes a

program that does not exist.

The error INVALID_OPERATION is generated if ExecuteProgramNV executes a

program that is not a vertex state program.

The error INVALID_OPERATION is generated if Begin, RasterPos, or a command

that performs an explicit Begin is called when vertex program mode is

enabled and the currently bound vertex program writes program parameters

that are currently being tracked.

The error INVALID_OPERATION is generated if ExecuteProgramNV is called and

the vertex state program to execute writes program parameters that are

currently being tracked.

The error INVALID_VALUE is generated if TrackMatrixNV has a target of

VERTEX_PROGRAM_NV and attempts to track an address is not a multiple of

four.

The error INVALID_VALUE is generated if GetProgramParameterNV is called to

query an index greater than 255 (was 95 in NV_vertex_program).

The error INVALID_VALUE is generated if GetVertexAttribNV is called to

query an <index> greater than 15, or if <index> is zero and <pname> is

CURRENT_ATTRIB_NV.

The error INVALID_VALUE is generated if GetVertexAttribPointervNV is

called to query an index greater than 15.

The error INVALID_OPERATION is generated if GetProgramivNV is called and

the program named id does not exist.

The error INVALID_OPERATION is generated if GetProgramStringNV is called

and the program named <program> does not exist.

The error INVALID_VALUE is generated if GetTrackMatrixivNV is called with

an <address> that is not divisible by four or greater than or equal to 256

(was 96 in NV_vertex_program).

The error INVALID_VALUE is generated if AreProgramsResidentNV,

DeleteProgramsNV, GenProgramsNV, or RequestResidentProgramsNV are called

where <n> is negative.

The error INVALID_VALUE is generated if LoadProgramNV is called where

<len> is negative.

The error INVALID_VALUE is generated if ProgramParameters4dvNV or

ProgramParameters4fvNV are called where <count> is negative.

The error INVALID_VALUE is generated if VertexAttribs{1,2,3,4}{d,f,s}vNV

is called where <count> is negative.

The error INVALID_ENUM is generated if BindProgramNV,

GetProgramParameterfvNV, GetProgramParameterdvNV, GetTrackMatrixivNV,

ProgramParameter4fNV, ProgramParameter4dNV, ProgramParameter4fvNV,

ProgramParameter4dvNV, ProgramParameters4fvNV, ProgramParameters4dvNV,

or TrackMatrixNV are called where <target> is not VERTEX_PROGRAM_NV.

The error INVALID_ENUM is generated if LoadProgramNV or

ExecuteProgramNV are called where <target> is not either

VERTEX_PROGRAM_NV or VERTEX_STATE_PROGRAM_NV.

(Modify Table X.5, New State Introduced by NV_vertex_program from the

NV_vertex_program specification.)

Get Value Type Get Command Initial Value Description Sec Attribute

--------------------- ------ ----------------------- ------------- ------------------ -------- ------------

PROGRAM_PARAMETER_NV 256xR4 GetProgramParameterNV (0,0,0,0) program parameters 2.14.1.2 -

(Modify Table X.7. Vertex Program Per-vertex Execution State. "VP1" and

"VP2" refer to the VP1 and VP2 execution environments, respectively.)

Get Value Type Get Command Initial Value Description Sec Attribute

--------- ------ ----------- ------------- ----------------------- -------- ---------

- 12xR4 - (0,0,0,0) VP1 temporary registers 2.14.1.4 -

- 16xR4 - (0,0,0,0) VP2 temporary registers 2.14.1.4 -

- 15xR4 - (0,0,0,1) vertex result registers 2.14.1.4 -

Z4 - (0,0,0,0) VP1 address register 2.14.1.3 -

2xZ4 - (0,0,0,0) VP2 address registers 2.14.1.3 -

Rev. Date Author Changes

---- -------- ------- --------------------------------------------

32 05/16/04 pbrown Documented that it's not possible to results from

LG2 that are any more precise than what is

available in the fp32 storage format.

31 08/17/03 pbrown Added several overlooked opcodes (RCC, SUB, SIN)

to the grammar. They are documented in the spec

body, however.

30 02/28/03 pbrown Fixed incorrect condition code example.

29 12/08/02 pbrown Fixed minor bug where "ABS" and "DPH" were listed

twice in the grammar.

28 10/29/02 pbrown Remove support for indirect branching. Added

missing o[CLPx] outputs to the grammar. Minor

typo fixes.

25 07/19/02 pbrown Fixed several miscellaneous errors in the spec.

24 06/28/02 pbrown Fixed several erroneous resource limitations.

23 06/07/02 pbrown Removed stray and erroneous abs() from the

documentation of the LG2 instruction.

22 06/06/02 pbrown Added missing items from NV_vertex_program1_1, in

particular, program options. Documented the

VP2.0 position-invariant programs have no

restrictions on indirect addressing.

21 06/19/02 pbrown Cleaned up miscellaneous errors and issues

in the spec.

20 05/17/02 pbrown Documented LOG instruction as taking the

absolute value of the operand, as in VP1.0.

Fixed special-case rules for MUL. Added clamps

to special-case clamping rules for RCC.

18 05/09/02 pbrown Clarified the handling of NaN/UN in certain

instructions and conditional operations.

17 04/26/02 pbrown Fix incorrectly specified algorithm for computing

the y result in the LOG instruction.

16 04/21/02 pbrown Added example for "paletted skinning".

Documented size limitation (10 bits) on the

address register and ARA, ARL, and ARR

instructions. The limits needs to be exposed

because of the ARA instruction. Cleaned up

documentation on absolute value on input

operations. Added examples for masked writes and

CC updates, and for branching. Fixed

out-of-range indexed branch language and

pseudocode to clamp to the actual table size

(rather than the theoretical maximum).

Documented ABS as semi-deprecated in VP2. Fixed

special cases for MIN, MAX, SEQ, SGE, SGT, SLE,

SLT, and SNE. Fix completely botched description

of RET.

15 04/05/02 pbrown Updated introduction to indicate that

ARL/ARR/ARA all can update condition code.

Minor fixes and optimizations to the looping

examples. Add missing "set on" opcodes to the

grammar. Fixed spec to clamp branch table

indices to [0,15]. Added a couple caveats to

the "ABS" pseudo-instruction. Documented

"ARR" as using IEEE round to nearest even

mode. Documented special cases for "SSG".

List of OpenGL implementations supporting the GL_NV_vertex_program2 extension

Original text file for the GL_NV_vertex_program2 extension

Page generated on Sun Nov 20 18:40:13 2005