BUG? reflection gone on certain objects in X amount of frames?

[Jens]

Hi

I'm having an issue where the reflection suddenly is completely black on certain objects in an animation i'm doing. Corona 10 hotfix2, 3ds max 2023. This is the first time I see it happen and it's been around 5000 frames rendered so far. I've checked if the object, object materials or lights had any accidental animated settings in them for this frame number, but all looks good.

Restarted the PC. Tried rendering in perspective mode instead of camera. Nothing changes the fact that for exactly these 4 frames, reflection is missing on certain objects!

Have tried deleting corona lights and making new ones. Still bug in these 4 frames no matter where in the scene I click "render". Be it with the corona camera or just in perspective

Ran sini forensic and deleted anim layers. No effect.

Am I missing something?

[Jens]

small discovery: it seems like in those 4 frames, all materials with a normal/non metallic fresnel IOR won't have reflections / appear in reflections pass.

[pokoy]

IIRC there was a thread/post here recently reporting something similar, only with mask visibility through refraction, where it would be missing for a couple of frames but ONLY on legacy materials, Corona Physical would render fine. Maybe a thing to look out for... sorry if this is misleading, just thought it might be related.

[maru]

What exactly is happening in that animation? Is it only camera movement, or something more?
Also, if you open that scene locally and go to those frames, do they render correctly or with those black reflections?

[Jens]

IIRC there was a thread/post here recently reporting something similar, only with mask visibility through refraction, where it would be missing for a couple of frames but ONLY on legacy materials, Corona Physical would render fine. Maybe a thing to look out for... sorry if this is misleading, just thought it might be related.

thank you! It's definately something with legacy materials acting up. I've just tried to replace a few of them and then they get their reflection back in the "bad frames". It's just a bit annoying if I have to redo materials now and it will probably require a complete rerender of enitre sequence (2200 frames) for it to be good.

What exactly is happening in that animation? Is it only camera movement, or something more?
Also, if you open that scene locally and go to those frames, do they render correctly or with those black reflections?

I have attached a gif. It's camera movement up some animated escalators. and refl pass of frame 181 (good) and 182 (bad). It renders the same at garagefarm.net cloud as it does locally on my computer.
I tried to apply high IOR (legacy) material to the objects bugging out and then it shows up fine in refl pass. Gave them back org (legacy) materials and it was also FINE! But then on next render they were bad again in that frame range (182-185)

[maru]

My idea is a bit random, but could you try backing up your scene (to keep the original version) then running the following two scripts:
1 - https://forum.corona-renderer.com/index.php?topic=41371.msg218935#msg218935
2 - https://forum.corona-renderer.com/index.php?topic=41371.msg219089#msg219089

This should disable all volumetric effects in your scene in Corona Physical, Corona Legacy, and Autodesk Physical materials. Perhaps the camera is moving into a "zone" in which it is affected by a non-closed object with volumetrics enabled.

[Jens]

My idea is a bit random, but could you try backing up your scene (to keep the original version) then running the following two scripts:
1 - https://forum.corona-renderer.com/index.php?topic=41371.msg218935#msg218935
2 - https://forum.corona-renderer.com/index.php?topic=41371.msg219089#msg219089

This should disable all volumetric effects in your scene in Corona Physical, Corona Legacy, and Autodesk Physical materials. Perhaps the camera is moving into a "zone" in which it is affected by a non-closed object with volumetrics enabled.

interesting, yes I will give this a try tomorrow. For now I will render out the 4 troublesome frames with phys material I have tried to match the old legacy ones. Then it will probably only be a tiny flicker only I will see ;)

[maru]

Hi Jens, do you have any updates here?
If it's the "camera inside a volumetric medium" issue, we also covered it here and added a script which should fix all materials in the scene: https://support.chaos.com/hc/en-us/articles/4528592571537-Corona-renders-black-screen-3ds-Max