15.1. Introducing 3D in ActionScript 3.0

Up to this point, you've seen the display list and Flash Player's coordinate space as flat; two-dimensional. Display objects can have a position, scale, rotation, and even a stacking order, but they can't escape the fact that they all exist on a flat plane. Of course, when you think of it, your screen is a flat plane, and what you think of as a 3D scene is really just a flat image rendered with the simulation of depth. This trick of rendering is not new, having been incorporated by artists in the 15th century; the trick is called perspective. Regardless of its age, Flash Player only adopted this trick in version 10.0. And believe it or not, drawing "in three dimensions" does come down to this one trick.

As an interesting aside, there is one transformation of a display object that I didn't mention earlier: skew. Skew doesn't have its own DisplayObject property like the ones I listed, but it can be added in all versions of Flash Player using the display object's transformation matrix (see Chapter 34), or visually in Flash Professional. Given that you can create the illusion of 3D by drawing a scene in a certain way (with a certain projection), there's actually another way to draw 3D that relies on skewing. This kind of drawing is a parallel projection. You may be familiar with parallel projections if you've seen schematic drawings — blueprints — or played three-quarter, top-down games like SimCity, Final Fantasy Tactics, Diablo, and so on. The problem with parallel projections is that parallel lines never appear to converge.