Raytracing is slow. Incredibly slow. Painfully slow. That’s because you’ve got to check a lot of things to accurately determine what you’re seeing, if it’s in shadow, if it reflects off of something, etc., so it helps quite a bit to be able to get an idea beforehand of where everything is. Enter octtrees.
We’ve got a picture of a model (in this case, the Stanford bunny model). It consists of thousands of tiny triangles that make a surface. Then, imagine a cube surrounding the entire model. If there are two many triangles in that cube, you cut the cube in to eight smaller cubes, and repeat. What this build is a tree where “busy” portions of the space get divided more.
And now for pretty pictures:
The bunny on its own. There are tricks to smooth it out, but I left it highly triangulated to better represent the idea.
Bunny with balanced wireframe octtree around it.
Profile of the bunny with a very deep octtree.
I’m finishing up the implementation, and then I’ll be using it as part of my octtree as a intersection speedup.