Volumetric grid: flicker in animation

[johan belmans]

I have an issue when rendering an animation with Corona volume grid objects. They flicker over time in the rendered result. The vdb file does not contain any animation.
I rendered the animation with Path tracing as the primary solver and secondary solver and I rendered it with Path tracing and UHD cache (with a pre-calculated cache (every 5 frames). In both cases it flickers.
The lights Samples Multiplier has a value of 8.0
There is no material assigned to the clouds. The shading settings can be found in the attachment.
Any help would be welcome.

edit: every frame is rendered with 20 passes

[TomG]

TBH there really does seem to be some animation there, perhaps in the step size, or quality, or perhaps in the absorption, because the pattern repeats - it starts detailed and dense, then fades over three frames, then holds for three frames, then jumps to yet less detailed and dense and holds for three frames, then goes and repeats the exact same cycle. Such a specific set of repeats seems unlikely to come from some render engine error. Can you open a ticket and send in the scene?

[TomG]

Or you could try adjusting the "Animation" parameters and see if the flicker effect changes along with it, e.g. don't use repeat since this is definitely a repeating cycle :) And your length is set to 9, which is.... 3 times 3, and that's the length of the repeat in your video, 9 frames.

[pokoy]

Do you happen to use a vdb file that has its resolution or version included as a numeric string in the filename at the end of the filename?
Something like '...v1', '...v2', '...v3' would cause the loader to interpret that as a sequence and repeat or loop it according to the vdb object's setting.

[johan belmans]

Thanks for the the help, the issue is solved. There was a numeric string at the end filename of the different VDBs in the same directory. I added a letter at the end of the file names but still the vdb's were loaded as a sequence in MAX. The easiest solution was one single vdb in a directory.

[Nejc Kilar]

Glad to hear you've resolved the issue and thank you for letting us know what went awry :)