POV-Ray

Currently, radiosity does not make use of the fact that pertubed normals would theoretically just require a different weighting of already-sampled rays, leading to the following issues:

• Honoring normal pertubations in radiosity leads to an increased number of samples, slowing down sample cache lookup.
• The increased number of samples is generated from a proportionally higher number of sample rays, slowing down pretrace even further.
• Low-amplitude pertubations tend to be smoothed out; “reviving” these is only possible by increasing the general sample density.
• Handling of multi-layered textures with different normal pertubations is currently poorly implemented.

As a solution, I propose to store for each radiosity sample not only the resulting illumination for a perfectly unpertubed normal, but from the same set of sample rays also compute the illumination for an additional set of about a dozen standardized pertubed-normal directions, and interpolate among these when computing the radiosity-based illumination for a particular point that has a pertubed normal.

For backwards compatibility, this method of dealing with pertubed normals in radiosity might be activated by a different value for the “normal” statement in the radiosity block, say, “normal 2”.