Is SimCity 4 3D?
- by Paul Pedriana, Software Engineer
The title of this article is "Is SimCity 3D?". I'm going to give you the answer right away and the answer is yes. The only difference between SimCity's 3D and a first-person game's 3D is that SimCity uses "orthographic projection" and limited view freedom. The intent of this article is to explain both of these differences and the reasons for the decision to implement them. Along the way I'll briefly mention some of the rendering techniques and used in SimCity 4 and the issues that come with them.
Orthographic, Isometric, etc.
I've stated that SimCity uses "orthographic projection." This is a term that's hard to describe but it means that the user views the 3D world as if all light rays going to the user's eye are parallel to each other. If you look at your computer and the room it is in, there are light rays coming into your eye from many different directions; they are certainly not parallel to each other. We call this non-parallel view "perspective" and first-person games use what's called "perspective projection." An exaggerated version of a perspective view is called a "fisheye" view where everything at the edges of a view are extremely warped. An orthographic view is the opposite of a fisheye view; all that you see is coming straight into your eye from directly in front of you, with all rays being parallel to each other.
Isometric is a term that refers to an orthographic view of a cube where all angles of view are 45° three sides of the cube are equally visible. Dimetric is a term that describes an orthographic projection of a cube where any two angles of view are the same (not necessarily 45°) as each other. Trimetric is a term that describes an orthographic projection of a cube where none of the three angles of view are the same. Many games have been implemented as isometric, though no version of SimCity has actally been isometric. SimCity 2000 and SimCity 3000 were dimetric and SimCity 4 is trimetric. Sometimes people refer to these kinds of orthographic views as "2.5D" views and refer to games like SimCity 3000 as having 2.5D graphics. The view is 3D, but the game doesn't have the flexibility to move the view about arbitrarily as with first person 3D games. In fact, SimCity 3000 and SimCity 4 internally are entirely 3D; only the user's view of the city is limited to certain positions and angles.