Bad shadows and artifacts appearing near edges and on surfaces

Started by tbroen, January 16, 2020, 06:10:25 AM

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Hi all. I'm facing some difficulties getting those crispy renders.
I'm rendering using Custom Control (50 samples, 5 Ray bounces, 3 Anti Aliasing, 2 Shadow, 1 Global Illumination) Which in most of the cases works just fine. But I'm having some issues with shadows and shadow artifacts in the images as shown on the image. The problems appear both in the middle of surfaces as well as near edges.

I tried to use Maximum Samples instead, where the problems disappear, but the renders look way more flat, so it is not a usable solution in this case. What can I do to eliminate the shadow artifacts?

Using Keyshot 8.2 Pro on Windows


When I've run into scenarios like this when using Custom Control (which I try to use as much as possible), here's my checklist. I would suggest trying these in sequence with a small region render to test the values vs. output.
1. Ensure that every material sample value is set to at least 16 (separate from scene samples, 50 might be too high).
2. Disable Global Illumination Cache.
3. Increase Anti-Aliasing value, this shouldn't affect your render time significantly. 5 is probably fine.
4. Increase shadow quality. In my tests, every step (1-2) is a about a 10% render time adder. Since this affects your shadows though, try going up on this before resorting to #5.
5. Increase your Global Illumination Value. This DEFINITELY affects render time, so try changing from 1 to 2, test, and if that's not significantly better, bump to 3, repeat.

Hope that helps, would love an update after you try changing these settings.


Great tips Richard - I have been playing around with all the different settings.
There are so many factors to play with that it becomes quite a puzzle to find the best compromise of settings.
In this case it turned out that disabling the Global Illumination Cache did the trick - I wish I had tried changing that setting first  ;D

This gave me a good result - Way better than before, and the artefacts are gone as well.
And changing the material samples from 9 to 16 also made the surfaces look more smooth.

Thank you for the tips - they were much appreciated :)


Awesome, glad this helped!

Yeah, I don't know what actually causes those spots (someone from Luxion may have to chime in) but IIRC GI cache seemed to usually fix it. In cases where it didn't (cloudy/translucent materials + lights seemed to be the most common trigger) the other steps helped but added render time. Glad you had an easier time fixing it :)