Can someone explain radiosity lighting to me?

Question

I already have the basics of ambient occlusion down. I have a raycaster and am capable of shooting rays about a hemisphere uniformly. It seems like those are the basics of what are needed for radiosity but I don't know where to go from there. Do I find how much light comes from each face? (I'm making my game out of cubes like minecraft) After that what do I do?

Answer 1

If you're interested in computer graphics "theory", I'd highly recommend Foley/van Dam:

http://www.amazon.com/Computer-Graphics-Principles-Practice-2nd/dp/0201848406

If you're just interested in what it is, and how it works, Wikipedia has a great article (with visual examples and math equations):

http://en.wikipedia.org/wiki/Radiosity_%283D_computer_graphics%29

And for an over-simplified one-liner, I guess you could say "radiosity is a more sophisticated technique for rending ambient lighting in a ray traced image".

IMHO ...

Answer 2

Radiosity, in simple terms, is a two stage algorithm to compute illumination. It works as follows:

first stage: For every pair of polygons in the scene, you compute "how much they can see of each other". E.g. take a cube: none of the faces see another face of the cube. If you invert the cube to a room: opposite inner walls see each other completely.

second stage: With this 'visibility information', called 'form factors', you can now distribute the light energy progressively through out the scene. At iteration 0, all the energy is in the light-source faces, and this is then transferred onto other faces. At subsequent iterations, more faces are transmitting energy into the scene (indirect illumination).

Drawback: does diffuse illumination only Strength: once computed, the lighting is viewpoint independent so that static scenes can be "walked through" without recomputing lighting.