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Normal UV's

Hi,

I have a object with a tileable stone texture with a diffuse and normal texture mapped to UV Channel 1 and on UV Channel 3 I have just a normal map trim sheet to add a second normal detail to a certain part of the UV’s.

My question is how do I combine these normal in the material editor to work together?

Thanks

You can’t use normal maps on anything except for the first UV channel, the normals are not calculated for the other channels.

This is correct, but as of 4.11 there is also a material function that can calculate the tangents and transform the normals for different channels. It is not perfect though as there can be seams in the lighting because the derived tangents won’t be interpolated the same way.

Read this answerhub post for more info:
https://answers.unrealengine.com/questions/395121/tangents-only-calculated-on-uv0.html

Generally its best to just use UV0 for normals, but this method is intended for cases where you really need to use other channels for some reason.