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Timeline for GGX energy conservation

Current License: CC BY-SA 3.0

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Aug 4, 2014 at 15:58 comment added Nathan Reed @Sikowsky And you can indeed use the BRDF directly in the shader, with point lights. Point lights are kind of a limit, in which an area light gets smaller while also getting brighter to maintain the same total power. In the limit the size goes to zero and the brightness (radiance) goes to infinity. Point lights have infinite radiance (actually the radiance is a delta function) so when convolved with the NDF they do correctly output very high values—just as an extremely small, extremely bright area light physically would.
Aug 4, 2014 at 15:55 comment added Nathan Reed @Sikowsky To comment on your follow-up question, "in reality" (or rather in the mathematical framework of geometric optics) the BRDF and incoming radiance have to be integrated over the whole hemisphere. Just like a probablity density has to integrate to 1, the NDF has to integrate to 1, so the total energy reflected is always ≤ the incoming energy.
Aug 4, 2014 at 10:11 comment added Sikowsky I have added an edit to the original question based on your answer. Thanks.
Aug 3, 2014 at 22:30 history answered Nathan Reed CC BY-SA 3.0