VDB flickering on cycles

This isn’t the first time I’ve come upon this issue, but I never managed to replicate it. Sometimes it goes away on its own, sometimes it doesn’t.

The issue is that when rendering VDB files with cycles, some of the VDB leaves/voxels render as empty, leading to flickering in the render. It looks fine on the viewport view and on any other software, but on cycles it leads to this flickering. I’ve tried increasing and decreasing step rate, max steps, density, but nothing seems to help.

I’ve attached a render below where this issue is very visible. Is this fixable? Does anyone have any idea why it happens?

Hi. Could you please share a reproducible blend.

By any chance, do you have multiple volume objects that overlap each other (especially if they have different scale values)? This can cause issues in Cycles.

http://blender-3d.338.s1.nabble.com/OpenVDB-Quickstart-Blender-2-83-tp186.html

Well this is awkard, but it seems the issue was as simple as increasing the transparent bounces.

Apparently Cycles treats each VDB leave as a surface, so you have a bunch of transparent bounces in there. Increasing it to 20 got rid of the flickering

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