I have a shader or lighting issue with substrate that is almost seeming like a bug. We are using unreal 5.7.2 to create vehicle renders with lumen. I have a paint material that is a substrate 2 slab based on the Xrite master. I am getting some artifacts that show up green or purple on certain paints. When I disable the clearcoat slab, the artifacts totally disappear. This obviously won’t work as a solution since clearcoat is detrimental to paint material. I have tried updating my graphics driver as well. These artifacts can be inconsistent to when they appear. I am able to get them to show up in the viewport if I view it full screen. Sometimes they disappear if I turn off the clearcoat and re-enable it. This is happening on 3 different computers with different specs.
From the advice of Aunmar, I have also:
Built 5.8 from source and moved our project over to that.
I have also in 5.8 tried:
Removed clearcoat slab (this does fix it but clearcoat is detrimental to the paint shader)
Removed glint
Clamping all values going into the slab to 0-1
removing specular profile
Simplified the render graph to be just a lumen deferred render ( no collections or material id)
Going through the different substrate settings in the project settings
Changing the materials shading model Default lit / Subsurface
Switching from 1 sided to two sided.
Changing the HDRI compression can reduce the issue but it doesn’t seem to totally eliminate it.
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Steps to Reproduce
I have a scene with a HDRI lit skylight and a couple of spotlights. The material I am seeing an issue with is a 2 slab substrate material that uses glint and clearcoat on the top layer. When I render a turnaround of the vehicle using the render graph I am noticing some brightly colored artifacts in this material. The issue shows up as a saturated blue or purple tint on some frames.
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Hi Vince, when you update the sample project you sent me in UE 5.7.2, do you still see the issue in UE 5.8?
Or are you seeing the issues in your custom project.
Aunmar
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This was still showing up in 5.8
Right now I am debugging in 5.7.2:
I think we have narrowed down the issue to rectangle lights. After a lot of testing things, keeping the whole scene the same but removing the 1 and only rect light does fix the issue. If I create a new rect light from the toolbar and just change its size and intensity it will create issues in the render again.
We had a rect light on light channel 1 which would create more noticeable blue artifacts. This was also present in the default rect light after adjusting light, size, and then changing the light channel from 0 to 1.
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We are running into the issue again after replacing the rect light with a spot light with some source radius and length. This is also causing similar issues when light channeled to 1. I’m thinking now this might have something to do with Cast Ray traced shadows on a light or possibly another setting on a light.
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Hey Vince, I plan to close this ticket as this ticket as this issue was solved with the UE Main patches.
Please create a new EPS ticket for the Movie Render Graph issue and lights and our team will review as soon as possible.
Thanks!
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Hi!
This thread is SOLVED?
What is “UE Main patches”.
Are these pathes in 5.8?
Thank you.
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Hi There,
Yes, this has been patched in UE 5.8.
Thanks
Aunmar
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