I’ve recently encountered an issue with Nanite meshes and visible UV seams. As you can see in the pictures, when I enable Nanite, the UV seams turn black. I can’t eliminate them by adjusting mesh settings, such as normal precision.
I should mention that I’m using UV operations with switch nodes to select the UV channel for each asset. The only way I can remove the black seams is by stopping these operations (which I can’t do, as I need that feature) or by disabling mip generation, which is not recommended for performance.
I would greatly appreciate any insights if anyone has experienced this issue or knows why it might be happening. It could be an Unreal bug that hasn’t been fixed yet.
You haven’t found a solution? I’m using a custom primitive data to modify UVs on meshes and have also encountered this issue. When adding logic to change UVs, visible seams appear when using Nanite.
I believe the reason for this is explained in this talk https://www.unrealengine.com/en-US/blog/take-a-deep-dive-into-nanite-gpu-driven-materials
The relevant section is page 23 of the PDF.
Essentially, it has to do with mipmapping and nanites manner of merging material rendering into a single full screen pass. Messing around with a nanite mesh’s UVs can interfere with the way nanite addresses this, causing a UV seam in manners that may not have been a problem with non-nanite meshes.
You may be able to solve it in most cases by manually calculating the correct mipmap in your material for the texture sampler.
