Glossy, metallic donut in Cycles reflecting itself with very bright noise

Question

I am trying to make a series of chains and metal fixtures with bearings on them in Blender 2.93, but whenever I use a glossy or principled shader (Metallic: 1, Roughness 0.2, everything else default), any sort of ring-like structure ends up having these a very bright, super noisy spots on the inside of the ring (not noisy with high samples, but they're still undesired)

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I tried messing around with Light Paths, Clamping, Caustics, but I wasn't able to get rid of this effect. The only time I get rid of it is if I disable Glossy under Ray Visibility of the Object Properties, but that also completely removes any shadows, which I need for where one object overlaps the other.

What's the best way to get rid of these ring-shaped reflections while keeping everything else working as intended? I'd like to keep the object glossy and reflecting the environment, but not itself. I'd still like to keep shadows in case I make notches or overlaps.

Edit: Even going all the way down on roughness results in a super dark ring on the inside of the ring, and I noticed that if I duplicate the ring and place it right in the middle of the other ring, it will reflect an image of the first ring like it's not around it, but in front of it.

Answer 1

I did some tests in a scene of my own, trying to recreate your scene and I was able to replicate this effect and also 'get rid' of it (kinda). Here's my theory...

I created the rings with full metallic and low roughness to try and match your image, then added a somewhat dark hdri environment and a point light. Here's what I got:

I think it's pretty similar to yours, right? With the bright ring reflection inside the rings that doesn't look very natural.

I then deleted my point light, and the result, although darker, looked much more natural:

So I guess the issue is that my point light just doesn't fit with the environment hdr map, and the light rays from my point light are bouncing off the curved surface and creating a really bright reflection, but because the material is so metallic and has little roughness, and the surface is very curved, the reflection looks out of place. You don't see any other effect of this point light except that bright reflection, so the reflection looks out of place.

When I remove the point light, the scene looks much darker, but more natural (or more 'coherent', at least).

Also, if I add something else to the scene, like a metallic plane underneath the rings, it also looks more natural, because is adds other highlights and reflections caused by the bright point light, so the scene lighting looks more coherent like this also:

And exact same scene as above, but with the plane's camera ray visibility disabled, so it's only rendered in the reflections and not in the background:

In my opinion it looks better, because the lighting looks more 'coherent'.

I don't know if you have a point light in your scene, but even if you don't, perhaps your hdr environment has a bright point that is acting like my point light. My suggestion is to add other objects in the scene, outside of frame (or only renderable in reflections), so they create other highlights reflected in the rings, making the lighting and reflections look more coherent.

Answer 2

It's more likely that the inside is the correct color, but rather the outside is unnaturally dark due to the lack of an environment for the metal to reflect.

If it goes away when you disable Glossy rays, then this is the reflection of the chain on itself.

If you want to eliminate the effect from this shader, you can use the Light Path node.

This setup should keep the first glossy bounce and switch to a Principled BSDF with high roughness for every bounce afterward.