Ok so here's what I've found by experiment: The anisotropic shader makes the highlight stretch to a line. The line's orientation on the model is determined by the orientation of the uv island. Negative aniso values make a vertical line as seen by the uv map, and positive values make a horizontal line. The further you move from 0 the crisper the line effect gets. Ok great. Now, I'm an artist. I dont code game engines. So I'd like to know what the guys that do code engines were expecting artists to do with this shader. I've been working on a horse model, and horses really benefit from aniso effects. However, there's no way to unwrap uv islands for a horse that will make the aniso's uv based shine work while still making it work with a texture. The problem is seams, and the fact that by definition you wont have the same uv island orientation at seams. So they introduce the 'tangent map'. I assumed I could use it to adjust the angle implied by the UV map, allowing me to flow the aniso effect along the fur's path. I was guessing it was 0-360 remapped to 0-255 and while it would be a pain, I figured I could make it work. No, thats not what it is. The map is an actual vector4 with a hint-bubble stating "BC7/BC5/DXT5(nm)". Seriously, what the flying F* am I supposed to make of this? DXT5 seems to be a compression standard, but the internet contains no data, nor does Unity's documentation. So, not one to be stopped by bad documentation, I wrote a shader and sent in a blank texture, but I used UV2 and mapped UV2 on the mesh to be a side-projection. In theory that might kinda work and there'd be no seams. No, it isn't using UV2. Since anisotropy is so 'uv based' one would think you could pick a 2nd uv set to base it on but they didn't seem to consider that. So I tried baking every known variant of every weird texture I could in xnormal. Nothing seemed to be a 'uv island compensator' so of course nothing worked. I'm not a mathematician, so I dont know what a BC7/BC5/DXT5(nm) tangent map IS, but I wrote another shader that let me manually enter R,G,B,A as sliders to see if I could manually guess a color for the different islands to get the sheen to line up. Of course I broke the mesh up into bits so I could test each island vs the body on its own. Fail. Turns out the tangent map is affecting the shadows, not just the anisotropic highlights?! Whats the bloody point of it all!? Its like adding a 2nd normal map. Yes, the sliders caused the sheen to wig-out, but when I got the sheen right, the shadows were munched. So, unity shader coders, could one of you please write a how-to document on how to use this thing? I'm not a coder, but I'm a good artist. I should be the guy you were planning on writing this shader for, and I give up. The brown horse is one mesh using unity's HDRP Lit with aniso. There's an island seam on the rump. The gray horse is 2 meshes, the back legs are separated and have a different tangent value plugged in to the tangent map. Note the shadow has been ruined. So the tangent map seems to be unusable, for if you did you'd be screwing not only with the gloss but the actual surface normals used in lighting? How was this INTENDED to be used. How would you use it to shade a horse like this?