UE5.5/5.6 Path Tracing Bug – Black Faces with Normal Adjustment Materials (FixRotateAboutAxisNormals, VAT, etc.)

Development Rendering
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1

Hi everyone,

I’ve run into a reproducible issue in Unreal Engine 5.5/5.6 when using the Path Tracer.

The problem:

  • Any material that adjusts normals to complement world position changes (for example, using FixRotateAboutAxisNormals or similar setups) renders with black faces in Path Tracer.

The same meshes and materials render perfectly fine in Lumen and rasterization modes.

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image1561×1137 72.4 KB

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image1588×1131 76.6 KB

Any help, insights, or confirmation from others seeing the same would be greatly appreciated.

Thanks!

2

Can you screenshot your material setup for me? I am not getting this.

3

FixRotateAboutAxisNormals:

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image1888×1381 311 KB

I also tried using world space normal, didn’t work either
(note the lighting is correct if the object don’t have any rotational offset, the closer it to original state the less artifact)

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image1777×973 75.8 KB

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image1822×978 76.2 KB

VAT material, I am using the “Vertex Animation Manager” plugin

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image1288×987 100 KB

the screenshot from the first post is the comparison with this material