The making of Sintel
The technical firepower
Some of these good workflows were facilitated by new features in Blender 2.5, the latest release of the software used on the movie (see ‘Under the hood’ opposite).
In particular, the software design philosophy that everything within Blender should be accessible through Python scripting, and that everything should be animatable, were vital to the success of the animation work, which called for more nuanced performances than previous open movies.
“Big Buck Bunny had a very squashy, stretchy rig,” says Reynish. “You could really pull it around. But Sintel had to be more constrained. Instead of a mouth you could pull in any direction, each element of the face had to have certain shape keys associated with it. It made things far more complicated.”
In addition to creating custom interfaces for the animation rigs, Python was used to script the ‘Rigify’ system, used to set up background characters automatically.
Whereas in Big Buck Bunny, each character had taken two or three weeks to rig, Rigify slashed development times.
“It’s really quite fantastic,” says Reynish. “You just define the basic proportions of a character using an armature and click Generate, and it sets up the rig.”
Under the hood: advancing the development of Blender
With one of the aims of open movies being to advance the development of Blender, Sintel became the first major project undertaken solely in version 2.5 of the software – then still in alpha.
“It was… well, not hardly used, but hardly finished,” comments producer and developer Ton Roosendaal.
Since visual realism was a key goal for the project, changes to Blender’s code base included support for micropolygon displacement to facilitate the development of new sculpting tools.
“It isn’t a [true] micropolygon pipeline in the sense that Pixar has, but we can now generate the geometry per render tile,” says Roosendaal.
The lighting engine has also been revised to lay the foundations of what will eventually become a true BRDF pipeline, with improved raytracing and approximate indirect lighting.
This work occupied development time that would otherwise have been spent refining Blender’s simulation tools: a decision that was to have important consequences for production.
“The smoke sims and fire worked fine, but the cloth and hair were a disaster,” admits Roosendaal. “We had to re-render things continuously because the hair sim did something surprising or ugly.”
Accordingly, several shots had to be scaled back, and plans for crowd simulation dropped entirely.
However, an unqualified success of Blender 2.5 was the reworked non-linear animation system, which offers a new dopesheet and revised graph editor, both of which proved critical to Sintel’s realistic facial animation.
“The animation system is at a really good level of quality,” says Roosendaal. “People who worked [on the movie and] have experience in 3ds Max or Maya all say it’s at the same level or better.”