Frustum Culling in Flash 10

Update: corrected a few glitches in the bounding sphere creation routine.

Optimization is always important. But when it comes to 3D for the Flash Platform, it’s an everyday battle. The first ideas that come to mind are to avoid:

  1. redrawing the same regions : each pixel value must be set once and only once
  2. rendering invisible objects : objects that are out of sight still take a lot of CPU horsepower

While Flash takes care of the first one in its very renderer, the second one is not handled. But that is something we can easily address!

The Technic

The method is called “frustum culling”. The big picture is that every mesh is approximated using a bounding volume (typically a sphere or a box). If the bounding volume is visible, the corresponding mesh is rendered. The two following pictures show the frustum culling caught in action:

The mesh is visible
The mesh is visible: TPS counter indicates 18900 triangles per seconds
Frustum culling in action (TPS counter indicates 0!)
The mesh is out of sight: frustum culling is acting and TPS counter indicates 0!

Code snippets and a live experiment right after the jump!