Radiosity
Actually, radiosity rendering is not commonly found in raytracers. From what I
understand (surely not enough <g>) the lighting model ups the ante one step
further than raytracing in that it not only calculates how light bounces from
one surface to another (reflections), but also how one "lit" surface will
illuminate another in the vicinity. If you've got a desklamp that throws a
fairly tight spot of light, take a piece of white paper and angle the beam of
light to a dark area of your desk – that's what radiosity rendering models.
I'm sure there's more to it than I explained, but I think that's the central
gist of it.
John Tissavary | LUNA cie, inc