Faceting in Render

[tshelton]

I am having an issue with these curtains. I rendered it and noticed some really bad faceting. It only shows up when I render, it looks perfect in the viewport. I also tried rendering it with Physical Renderer in Cinema 4D, and it didn't have the issue. I have only seen the issue in Corona. Any ideas what may be going on? When I imported the mesh, it was triangulated. The gray and black curtain are both still triangulated, the white one I ran the untriangulate command and it didn't solve the issue.

[JViz]

try this. apply normal and normal modifiers then smooth auto modifier.
ignore that actually, that's for 3ds max

[Nejc Kilar]

Have you tried messing around with the Phong tag?

[tshelton]

Yeah I messed with the phong tag but didn't have any luck. I deleted it and re added it, I also changed the angle and that didn't help either.

[Beanzvision]

Hi, are you able to share the scene with us via our private uploader?
https://corona-renderer.com/upload

[tshelton]

I have uploaded that file

[Beanzvision]

Thanks for the file. I have looked at the scene and have made a few small changes. I untriangulated all the curtains, selected all the points and then used the optimized command to make sure nothing was disconnected. The phong tag wasn't doing its job so I created a sphere and copied the tag from that to the curtains. Finally, I dropped everything into an SDS modifier to add additional smoothing (this is optional of course). And I get the result as follows:

I'll send you a PM with the updated zip.