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I created a geometry node to randomly scatter instances on points (each one just a single face) across a base model surface, then divided those instances into multiple material groups with their own unique alpha textures. The end result is supposed to be sequins (instances) on fabric (base model). Each face is a square, so the alpha textures were needed to make the sequins circular when rendering. I’ve got about 4,500 “sequins” per material/UV, but when I apply the geometry node, select by material, and unwrap, I lose all the alpha textures and wind up with 4,500 perfectly mapped squares, but the circle alpha image is projected just 1 time over the entire map instead of sticking to each sequin, which obviously doesn’t work. Is there a way to get the alpha textures on each sequin to stick to the individual faces during the unwrap process? If not, is there some other way to reapply these alpha image textures to each “sequin” face easily after unwrapping? I’m very new to Blender and geometry nodes so hoping there’s a simple procedure for this!

This is what the sequin faces look like with the alpha texture before rendering. This is what the sequin faces look like with the alpha texture before rendering.

This is what the sequins look like when rendered. This is what the sequins look like when rendered.

After applying the geometry node, selecting 1 sequin group by material, and unwrapping, this is what the UV looks like. As you can see, the faces are no longer attached to the alpha image textures, so now the render causes them to appear as black or gold squares instead of circular sequins. After applying the geometry node, selecting 1 sequin group by material, and unwrapping, this is what the UV looks like. As you can see, the faces are no longer attached to the alpha image textures, so now the render causes them to appear as black or gold squares instead of circular sequins.

I tried all the unwrap features hoping one of them would adhere the alpha textures to the UVs and preserve their position on each individual face, but none worked that way. So I’m left not knowing how to reapply the textures correctly and there are tens of thousands of sequins across multiple maps, so doing it manually isn’t an option.

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  • $\begingroup$ An image (what an alpha texture basically is) is never unwrapped. It is a 2-dimensional rectangular flat texture. Faces of a mesh are unwrapped and somehow placed in a UV map in one form or another so that pixels can be mapped to coordinates of the UVs (simply spoken). Now the question is how you get those different alpha maps onto the instances... because usually when I try this with a simple setup, after applying the Geometry Nodes modifier the separate parts keep their respective materials, UVs etc.? So you have to specify what you are doing, maybe with screenshots or an example file? $\endgroup$ Commented Sep 1, 2023 at 15:50
  • $\begingroup$ @GordonBrinkmann Thank you so much for your quick reply! Pardon my original phrasing, more accurately--I'm trying to figure out if there's a way to make the alpha image textures "stick" to the faces as the mesh is unwrapped. I have edited my original post with images and descriptions! Let me know if this helps! Thank you for your time! $\endgroup$
    – tifforelie
    Commented Sep 1, 2023 at 17:15
  • $\begingroup$ I don't this you need to unwrap it at all. they should all have the same overlapping uv map are, which I think is what you want. (you could randomize in the material with instance attributes). there is no need for realize instances in this. also please send nodes [image(s)] - this is a must for us to get a true grasp of the situation. $\endgroup$
    – shmuel
    Commented Sep 8, 2023 at 3:38

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