wuly@vax5.cit.cornell.edu (05/02/91)
Howdy. I have written a combination radiosity/raytracing rendering system (whew!) and I'm somewhat confused on one point: I have a scene of 5 walls, 10x10, with a light 3x3 pointing at one of the walls. Now with 90% diffuse surfaces, the relative energy out of the wall *behind* the light (i.e. light left the lightsource, hit the wall in front, and was re-radiated to the back wall, and re-radiated again) is about 1/1000 the energy leaving the light. This seems wrong. When one turns on a light, even a single 40W pointed at the ceiling in a dark room, you can see everything, whereas if the patches in my environment are rendered with visual (pixel) intensity linear with radiated energy from the patch, you can only see the lightsource, since everything else is so dark. I compensate for this by scalig the patch energy to pixel intensity s.t. the parts of the scene that would be dark in "real life" come out dark on the display. Anything (the lights + what is directly in front of them) goes beyond the insensity range of the display, so I clip them to the max displayable intensity. I see two possibilities: (1) the conversion from radiated energy to pixel intensity should be logarithmic, not linear. (2) I'm not computing form factors accurately enough (actually this is fairly likely) and much energy is just "slipping through the cracks". Can someone who has dealt with this issue EMAIL me your experience? Should I get a fairly well-lit room with a single large light? What is a good diffuse coeff for a white wall? thanks............................................................jesse wuly@vax5.cit.cornell.edu