Thank you for your reply, let me rephrase my question. I've created a shader that blends two normal maps on an object with two UV sets. - The (first) main normal map uses the built-in tangent basis based on UV0, no problem here. - The (second) detail normal map is created to use the tangent basis based on UV1 but uses UV0 by default too, so this results in incorrect normals. Question: Is there a way to set the secondary normal map to use the tangent basis based on UV1? From reading it's description, I was under the impression that the "Derive Tangent Basis" function could be used for normal mapping for UV1, but I'm not sure if I understand it correctly. Thanks!