Strange shadow + GI bug

[barnabash]

Hi there! I am having a strange bug and I would really appreciate some help as I tried many days to solve it and failed.

I have an image sequence of an interior with HDRI exterior lighting, some IES lights, some rope lights, some mesh lights etc. Thes scene is fairly complex but nothing too crazy or something I haven't done in vray without any issues before.

I want 7 shots, and the way I do it is that I animate the camera and then render the animation sequence and this seems to be the root of the problem.
From the 4th frame onward, the shadows and GI are messed up. If I render the exact same frame as a single frame, everything looks good, the image is perfect, but if I render the animation sequence, after a couple of frames the GI and shadows become messed up.

Any idea how to resolve this other than the obvious "ditch the animation sequance" solution?

I attached a small example of the bug. 1st image is wireframe, second is when I render as a single image, the third is the bugged when I render as part of an animation sequence.

[romullus]

I think there was a similar case recently and the solution to the problem was to disable adaptive light solver (or maybe it was adaptive environment sampler, or GI solution adaptivity - can't recall exact setting). Either way, you may want to give it a try and see if that helps.

[barnabash]

I think the problem is solved, thanks a lot romullus! The solution seems to be unchecking "Enable adaptivity" under Adaptivity and Denoising.

[romullus]

I'm glad to hear that the workaround has worked. I think Corona team may want that scene for testing purpose, since they definitely will want to fix the issue properly.

[barnabash]

Looks like I spoke too soon. On the hiogher resolution render overnight the same problem came back :(

I'll try disable other adpativity settings.

[romullus]

Moving the topic to bug reporting board, so that someone from the support team could take over and investigate the issue.

[pokoy]

Some thoughts - similar artifacts can be caused by multiple things:

- If you're using any kind of GI caching, make sure it's recalculated every frame
- Could be the adaptive enviro sampler as said above
- Do the affected materials use a Rayswitch mtl with different materials for GI and Reflection?
- Are you using a HDR bitmap in dome mode? If so, is your geometry below 0 in z-axis? Similar artifacts can occur if this is the case, in that case you could try to translate the map to negative z-axis values encompassing any geometry (within the CBitmap settings)

But it's sure strange that you're seeing this only when rendering the animation and not with single renders.

[barnabash]

Okay the problem seems to be solved this time for real as it worked on the high res final render.
Under the "Lights" tab I set
Enviro sampler: precise
Solver: scalable

[barnabash]

Some thoughts - similar artifacts can be caused by multiple things:

- If you're using any kind of GI caching, make sure it's recalculated every frame
- Could be the adaptive enviro sampler as said above
- Do the affected materials use a Rayswitch mtl with different materials for GI and Reflection?
- Are you using a HDR bitmap in dome mode? If so, is your geometry below 0 in z-axis? Similar artifacts can occur if this is the case, in that case you could try to translate the map to negative z-axis values encompassing any geometry (within the CBitmap settings)

But it's sure strange that you're seeing this only when rendering the animation and not with single renders.

Well to be honest I'm not quite sure what triggers the artefacts. On my single frame previews everything looked fine but the resolution was lower than the final render. I waited 30+ passes  when the artefact usually apprears but it didn't so I thought it must be the animation sequence because on my test it triggered the artefact on my preview. Bu then I didn't test a high res single frame version.

[maru]

This looks like the "black highlights" issue caused by materials with non-physical properties such as no shadowcasting or light mtl with no emission: https://support.chaos.com/hc/en-us/articles/4528311915025-Known-bugs-and-limitations

[barnabash]

Any workaround possible when this issue is cause by Corona Sun like in my case? Disabling adaptivity works but it also increases rendertime.