Some questions about multiple UV maps on skeletal meshes

Development Rendering
1
  1. How many UV maps can you have on a single skeletal mesh?
  2. What are the performance implications of having many UV maps?
2

Each UV is a float pair so something like 8 bytes per uv per vertex.

In terms of performance, the uv data takes up space, each additional texture map takes up a bound texture in the shader and time to look up the pixel.

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I found out that you can have 4 UV maps per skeletal mesh, the max is 8 per pixel and the other 4 maps are the customized UVs. I guess it’s kind of weird 4 are set up to be the customized UVs even if you’re not using them, but I guess having 8 different UV maps on a single skeletal mesh isn’t too common.

Anyway, I’m scrapping this idea right now because of workflow issues with this technique in UE4, Blender and Substance. It would save a bit of texture memory but not really worth it in the end. It’s probably a lot more nice to work with on static meshes. You would just need to use DeriveTangentBasis for the other normal maps.