PhotonGI strength

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lacilaci
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PhotonGI strength

Post by lacilaci » Tue Aug 13, 2019 8:30 am

While doing some testing I found out photongi to be a little too strong with lighting.

here's sun and sky in luxcore without photongi:
luxcore_sunsky_5min.jpg
for comparison here's cycles:
cycles_sunsky_5min.jpg
now of course it's different and very hard to match them cause sun and sky in cycles works terribly, but overall lighting distribution seems more or less the same, nothing weird is happening...

now here's photongi with default values in blender:
luxcore_sunsky_pgi_5min.jpg

you can see how is the scene flooded with light with objects on the ceiling almost looking like some fake AO is going on.

And here's photongi with photon depth set to 3 (default in blender is 8):
luxcore_sunsky_pgi_depth3.jpg
now the lighting is much closer to the non-pgi render while performance boost is still present


So my question is, what is happening with more photongi bounces/depth that gives this strong lighting?

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Dade
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Re: PhotonGI strength

Post by Dade » Tue Aug 13, 2019 4:41 pm

I have the feeling it may be more related to the bias of PGI when working with glossy surfaces (try to di the same test with only matte) ... and, you know, next week, when back in town.
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lacilaci
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Re: PhotonGI strength

Post by lacilaci » Tue Aug 13, 2019 5:36 pm

I did few tests with production scenes and it does look like a lot of reflections go wrong often when using pgi...

I'll try to make a good example case once you're back.

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Sharlybg
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Re: PhotonGI strength

Post by Sharlybg » Tue Aug 13, 2019 6:47 pm

Sorry but I don't really trust your current test scene. ;)
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lacilaci
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Re: PhotonGI strength

Post by lacilaci » Wed Aug 14, 2019 1:37 pm

So it appears this is happening only on disney shader.

glossy
glossy.jpg
disney
disney.jpg
I'm not surre though which result is actually correct cause glossy shader has it's own problems (the edge darkening)

there's also some opencl artifacting due to ngon triangles on the wall(CAD tesselated geometry), unrelated to this issue but it would be nice if opencl rendered things the same as cpu so that we don't get nasty surprises on final renders.

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