Color Banding Through Glass

monson67 · October 19, 2020, 12:47:12 PM

Mac OS 10.15.7 Catalina
iMac Retina 5K, 27-inch, 2020
3.6 GHz 10-core Intel Core i9
AMD Radeon Pro 5700 XT
KeyShot 9.3.14

I'm having an issue with color banding when I have a metallic paint material behind a glossy glass material (The area around the camera). This can be seen in the first image. Note that there is also a rough glass material (The rest of the back of the phone) in front of the metallic paint also. The location of the center of the color banding seems to be in relation to where the light reflects directly from and back into the camera (similar to closing one eye, and with the open eye, looking into a mirror at the open eye's pupil).

In the second image, I changed the metallic paint to a plastic material, and the issue goes away. So it seems specific to metallic paint behind glossy glass.

I've tried changing numerous settings in the materials (that won't affect the intended appearance), but I haven't had much luck. I've also attached the .ksp file (with only the necessary geometry, due to copyright) for anyone that wants to take a look.

Edit: I also considered Z-Fighting, so I tried moving the glass in relation to the metallic paint. No difference in effect.

designgestalt · October 19, 2020, 01:07:16 PM

hello Monson67,
unfortunately I do not have the time to take a look at your model, but there is one thing I can think of:
could it be, that there is no gap in between the glass and the housing of the phone? so that basically the glass touches the housing.
this sometimes causes trouble, because two surfaces are overlapping.
it might be, that what you see could be caused by that and that one material reacts differently to this than the other.
so I would place that glass just a very tiny distance away from the housing and see what it does...

hope that helps!
cheers
designgestalt

monson67 · October 19, 2020, 01:20:59 PM

I forgot to mention that in my initial post. I had considered Z-Fighting, and I tried moving the glass and the metallic paint in relation to each other. No difference in effect.

Eugen Fetsch · October 20, 2020, 01:51:21 AM

Tested your KSP in KS9 and KS10beta ... can't reproduce the issue - no banding.

Zeltronic · October 22, 2020, 06:42:10 AM

Test it too and no trouble as well...

TGS808 · October 22, 2020, 10:39:44 AM

The previous two posters must have gotten the magic version of KeyShot because I opened your file in KS9 and the concentric circle banding is definitely there. I don't have a solve but wanted you to know, it's definitely not just you.

monson67 · October 22, 2020, 12:03:37 PM

Well, it's good to know that it isn't just me. Thanks for taking a look at it.

Zeltronic · October 23, 2020, 12:52:33 AM

I don't Know if we have the magic version (9.3 in my case) but I confirm that I have no banding issue with your file ... To put me at the same level of highly technical explanation I would say that you may have the evil version

Eugen Fetsch · October 23, 2020, 01:45:54 AM

It may be a hardware or driver issue. Did you concidered to contact Luxion with your machine specs?

monson67 · October 23, 2020, 05:52:10 AM

No, I hadn't. I will probably do that. And since you mention it, I think I will edit the original post to include my machine specs, in case anyone has similar issues.

andy.engelkemier · October 26, 2020, 06:34:16 AM

Well I didn't get That, but I did get a completely Different crazy keyshot issue. I checked in regular as well as GPU mode also.
I took a video of it because I didn't think you'd believe me if I told you.
You only see the selection when the camera is paused, so I had to move and pause, move and pause. But when the camera is above, the selection is behind the object. When rotating down to the side, it's at the front?

I kind of wonder if your camera is jacked. Since you only have the free cam you can't really "reset" it without getting a different camera in the scene. I imported that into a new scene and it was fine.
Often enough I just get errors that don't mean anything to me. Like, "invalid id_4651651" or something like that. And I just ignore it because I need to finish. But I am guessing the same kind of thing can happen with other things, like cameras.

See if your banding goes away if you import it into a new file.

TGS808 · October 27, 2020, 07:32:55 AM

I tried it on 9.1 and 9.3 on Mac. If I open the file and just let it res up, there is banding on both. Could it be a Mac/Win thing?