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I'm rendering an animation (as an .exr image sequence) and some images have these tiles appear on the final render. It somehow only happens on surfaces that are closer to the camera. It looks like Blender is somehow calculating adjacent tiles differently in certain areas.

You can see them on this image as the faint, slightly darker squares. The distribution of these boxes in random every render-iteration.

Has anyone had the same problem? I've tried turning denoising off, changing the tile sizes, changing the sampling or changing the light paths etc., nothing helped.

enter image description here

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  • $\begingroup$ Hmm, this is quite weird. Have you tried any other file type? Does PNG and or JPEG work? $\endgroup$ – Askejm Jul 19 '19 at 19:44
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    $\begingroup$ Are you rendering on CPU or GPU? Try switching to just CPU to see if that helps. $\endgroup$ – Rich Sedman Jul 19 '19 at 19:45
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    $\begingroup$ @RichSedman both. good thought... that may actually be the cause... different hardware, different output. although that does not explain, why those boxes only appear in this particular scene, where the camera gets closer to the terrain than in the others... (i'll try once my current render finishes) $\endgroup$ – chribit Jul 19 '19 at 22:29
  • $\begingroup$ jep, that actually was my first thought too. But nope, same problem with any other single-image filetype (didn't try the movie filetypes... shouldn't make a difference though). $\endgroup$ – chribit Jul 19 '19 at 22:31
  • $\begingroup$ I know this is going to be very general but could you explain more about your setup, if you are doing anything in the compositor, or if you are running any scripts or doing anything special $\endgroup$ – Ben Jul 19 '19 at 23:42
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Figured out the cause thanks to @Rich Sedman, so I guess this is a temporary "solution", as it doesn't really solve the problem, just finds a way around it.

The tiles appear in the render due to CPU and GPU handling the output differently for some reason. Deactivating the CPU in the CUDA settings not only solved the issue but also gave me 30 seconds faster render times per frame.

Not sure if that's an issue of the current 2.8 release candidate or just something that comes with combining two pieces of hardware for the same process. (Maybe my Geforce GTX 1080 ti doesn't work well with my AMD Ryzen 7 2700X?)

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  • $\begingroup$ If cpu and gpu produce different results then you should report it as a bug. $\endgroup$ – sambler Jul 24 '19 at 3:15
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The opposite can happen too. My animation had bad tiles on three frames. I ran the frames over again with the exact same errors. Following the advice in this string, I turned ON CPU and GPU and bingo, problem solved.

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