What Is Radiosity?

Posted on Tue 13 October 2026 in tech • Tagged with gman, renderman, radiosity, graphics

Radiosity renders the light that bounces off matte surfaces.

Since light from the bulb is focused downward, none of it reaches the ceiling directly. This is a problem because a ray tracer, which does not see indirect light, paints that ceiling black.

Direct light Radiosity
a white box with a red left wall and a green right wall and two white spheres on the floor, lit by a bulb hanging under a green cone shade; the ceiling, the shadows and the undersides of the spheres are black the same box with bounce light: the ceiling glows a soft warm grey around the shade, pinker toward the red wall and greener toward the green; the shadows under the spheres fill with a dim, tinted light; the left sphere blushes brick red on the side facing the red wall and the right sphere picks up green from the green wall

The left render, lit like …


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