This week I have been busy completing the indirect lighting part of my project, but this turned out to be harder than expected. The problem was not particularly the algorithm itself, as I’m currently implementing a naive variant. As a reader pointed out, the state of the art in instant radiosity is currently Metropolis Instant Radiosity by Benjamin Segovia, but implementing that is not trivial and is left as future work.
I actually had a hard time figuring out how to read surface colors, which is something I need to color indirect lights and obtain color bleeding in the end. In the end I came up with some very hackish code that for sure wouldn’t be accepted in trunk. On the other hand I can’t see a cleaner way to do that without some changes in the existing Blender codebase. I have to talk to some other developer and see what’s the best thing to do.
Anyway, right now I have the ability to generate 1st and 2nd bounce indirect lighting from area lights, taking colours into account. I was able to obtain a rendering like this one:
The interesting thing is that this model was previously lit by a very complex lighting setup in order to fake indirect lighting. This rendering was obtained by placing a single area light behind the window.
Here are some more tests: