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QMC GI creates odd light patterns on mildly complex objects
I had to bail on Irradiance Cache for a GI method (reasons described in different post), which of course leaves QMC.
I have noticed an issue in multiple scenes with QMC, and was wondering if anyone else experienced the same, or knew what the problem was.
Specifically, on objects with fine/sharp/deep angles, where the illumination is trying to reach a thin area, it does some odd shading. I can’t tell if it’s light that’s not supposed to be there, or occlusion that’s not supposed to be there.
Check out the pic:
I’ve also seen it occur with the default ‘baseboards’ with the new House Builder (NitroMan), as well as a the canned bed spread (Blanket 02) in the Visualize content.
I’ve tried:
– Removing Ambient Occlusion
– Removing all textures
– Reducing the scene to one light source (sun)
– Removing secondary GI method
– Increasing Accuracy of QMC to 90%
– Playing around with Discrete Area/Sky Sampling
– Simplifying extruded splines in hearth
– Other Phong options
– Other spline ‘Type’ and Intermediate Points settingsWhat am I missing?
Here’s a version of the image with less compression.
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3 Replies
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Something else worth mentioning: in lower light, the issue is accentuated. Also, I get the sense the pattern moves from render-to-render.
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And a shot of the baseboards I mentioned:
This may be a scale issue. I’m working in Inches, and a lot of these errors occur in the smaller/thin objects. Also, the pattern is a giveaway. Will investigate further.
Hobbyist level. Used C4D since R14. Now on R16.
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You’ll probably need to increase the sample count. In the GI general tab, set samples to “custom sample count” and bump samples up until the artifacts start to clear up.
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