[RESOLVED] problem with certain camera position (shiny objects)

[tuami]

hello,
we have the problem that from time to time the renderings look like this, that the reflection on the floor is missing and the objects appear strangely reflective or shiny. we then noticed that if we move the camera slightly, the problem will no longer occur. we are currently rendering a small animation of 200 frames and here the problem is again with individual frames that again leads to the error. we would like to know how we can fix the problem without rendering every single frame beforehand to see if the scene is rendered cleanly, which would cause a lot of work and is not the solution to the problem.

we are using corona 11 final with c4d 2024 (we also had the problem with c4d r21 and older corona versions.

thanks
tuami

[maru]

I am not sure, but I think this may be caused by some kind of non-solid geometry (something non-capped, like a flat plane) with volumetrics enabled. In such case, when the camera enters that object's volume, this changes how IOR is calculated which can result in changes in other objects reflections and refraction.

To troubleshoot this, you can try running interactive rendering, moving the camera to the position where the issue appears, and then hiding your scene objects one by one. If you hide the problematic object, the issue should go away. If that's the case, you can:
- hide the problematic object forever (if possible)
- change the problematic object's material - for example disabling refraction or switching from solid to thin refraction mode - the idea is to make sure that the camera is not inside some non-capped volume with an IOR value other than 1.0
- capping the problematic object or giving it some thickness

Another idea to approach this would be to hide all objects except the camera and unhide all other objects one by one.

[Beanzvision]

In addition to my colleagues points, Where is the model from? What's happening in the animation, are they moving or is the camera? Can you share this scene at all?

[tuami]

Hello guys,

i think i have solved the problem.

The light material and the glass material are tagged on the same polygons, underneath there is a light to control or intensify the light effect.

If i delete the glass / or delete the light material it works, it would have been better to create it with two geometries, but i just delete the glass material because you can't see it anyway.

As the problem only occurred sporadically with the still images, we only ever moved the camera very slightly and the problem was no longer there, but the animation caused it to reappear in around 10 out of 200 frames.

thanks for the quick support, this can be moved from "corona bugs".
greetings
tuami

[Beanzvision]

Thanks for the update on this. :)

[maru]

So it was the issue that I mentioned, right?
The camera was inside a boundless object with a volume material applied to it? (solid glass)

If that's the case, please note that:
- solid glass (with refraction) should only be used on solid objects (objects with some thickness, not things like flat planes)
- if you want to use glass on a non-solid geometry (like a flat plane), you can use the "Thin shell (no inside)" option.

Generally, using the "Thin shell (no inside)" option in your scene would most likely solve the wrong rendering problem.