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Is it possible to use bidirectional path tracing to render an indoor scene where the light source is skylight(no sun) coming through a window? I think I roughly know how this is done if the light source was the window rectangle itself acting as a diffuse source but cannot get my head around on how it would work if the source is skylight and the camera is in a room: Is it the window shape that needs to be sampled or the sky dome? Would the light sample point be picked from the whole sky dome, or just a visible bit from the window?

ali
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Assuming no clouds floating just right behind the window, sampling the window shape is enough. You can just vary the spectrum of incoming light with the ray direction to simulate color gradient due to atmosphere.

Miloslaw Smyk
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  • Thanks @Miloslaw But how about accounting for the outside obstructions. The sample point the window shape and it's sampled direction can have zero length as the ray coming from sky might be blocked by outside obstructions. – ali Nov 30 '16 at 09:02
  • Well, if you have objects outside of the room which are not very distant (I alluded to that with my "clouds right behind the window" comment), then obviously you have to trace rays outside, too. – Miloslaw Smyk Dec 01 '16 at 08:14