Add new Layer/Mask Type: "UV Border Distance"

[andycuccaro]

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Describe The Feature Request Below

Currently, Ucupaint lacks a UV Border Distance generator, which is a fundamental™ tool available in software like Substance Painter. This makes it difficult to create procedural effects that depend on UV seam proximity, like those needed when texturing clothes, such as stitches alongside UV seams, masking alongside seams for applying wrinkles only there, etc.

Proposal: Add a "UV Border Distance" generator to the "Generated Layer" category, similar to existing generators like "Ambient Occlusion" and "Edge Detect". This generator would:

• Calculate distance from each pixel (or UV coordinate) to the nearest UV border/seam
• Output a grayscale map where black = maximum distance, white = on UV border
• Support explicit UV seams and, probably, automatic UV border detection for open meshes (like a disk, a plane, stuff like that).
• Support being added as a Generated Mask (thus, having Invert, Ramp, and Curve modifiers).

Its usecase can be seen here: https://www.youtube.com/watch?v=6wiqysx0Dq4&t=226s

PS: From what I understand, the UV borders could be detected using bmesh.types.bmesh.types.BMEdge.seam.
I've been playing with Claude AI to see if I could maybe implement it, but since I'm not a coder, I can't fully understand if the code it outputs make sense. I can share it, if you think it might help in some way. The idea would be to generate a function or field by detecting the UV seams and calculating the distance to the UV space border, to other other UV Islands, and inside the island itself.

[ucupumar]

Hmm, i don't think it's a good idea to create a new type only for uv seam data. Currently you can load uv_seam attribute in geometry nodes and use the output in ucupaint by opening available vertex color (I know it's a bit confusing since vertex color is the same thing as attribute in blender).

The problem with using attribute data directly is the data is per vertex so the line width won't be consistent across your model. Probably there's a way to bake/paint uv seam data to an image with consistent width, but I dunno how to do that yet.