Forums Technical Discussion COPs flow across UV islands

COPs flow across UV islands

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frxnlab
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Hi all,

Just started learning COPs and already my brain has been broken. I'm hoping someone can perhaps point me in the right direction.

(I've uploaded ref images in the hopes it helps to makes sense of my question)

Basically I tried to experiment with a flow texture on piece of geometry. I wanted to find the starting positions by baking it from a reference geo. I then fed it into a flow block but then quickly realized it wasn't going to be flowing across UV island borders in a similar way to Substance Painter.

Is there a way to achieve this flow that I am unaware of? I Googled as much as I could but didn't find an answer.
Edited by frxnlab - Sept. 17, 2025 02:48:38

Attachments:
Flow_04.png (635.5 KB)
Flow_01.png (249.3 KB)
Flow_02.png (35.9 KB)
Flow_03.png (429.7 KB)

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Konstantin Magnus
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I don't think there is a built-in node for this yet but Mattias Malmer created a setup for UV adjacency:

https://github.com/3Dmattias/Houdini_Escapades/tree/56b96a34d856d56c8d344e2cba7e24c18290222e/hip [github.com]
https://procegen.konstantinmagnus.de/ [procegen.konstantinmagnus.de]
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GrahamDClark
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As well as Mattias Malmer's solutions have a look at Yancy Lindquist's https://vimeo.com/yancyquist [vimeo.com]
Yay! I'm certified! https://media.sidefx.com/uploads/accounts/badges/certified_instructor_badge_AkLiM3h.svg [media.sidefx.com]
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Konstantin Magnus
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To let textures flow across UV islands, we could also pre-store offset sampling positions on a separate map to be picked up by a streaking solver.

https://procegen.konstantinmagnus.de/flowing-textures-across-uv-boundaries [procegen.konstantinmagnus.de]


Edited by Konstantin Magnus - Sept. 24, 2025 04:10:40

Attachments:
tex_flow_cops.jpg (92.0 KB)
tex_flow_across_UVs.hip (311.1 KB)
tex_flow_title_02_small.jpg (35.5 KB)

https://procegen.konstantinmagnus.de/ [procegen.konstantinmagnus.de]
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Konstantin Magnus
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I have added a COPs only version.

Is there a COP node that can replace xyzdist + primuv so we can get rid of the wrangle?
Edited by Konstantin Magnus - Sept. 24, 2025 16:34:45

Attachments:
cops_tex_streak.hip (335.3 KB)

https://procegen.konstantinmagnus.de/ [procegen.konstantinmagnus.de]
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tamte
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Konstantin Magnus
Is there a COP node that can replace xyzdist + primuv so we can get rid of the wrangle?
in your case when taking small steps you can probably replace it with Raytrace COP, use your offset P as origins, rasterized N as directions and sample the "uv" attribute (as RGB then convert to UV )
Tomas Slancik
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Framestore, NY
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Konstantin Magnus
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Thank you Tomas, I was hesitant with this but it seems to work.

The 'position sample' node also looked like a suitable candidate initially:
https://www.sidefx.com/docs/houdini/nodes/cop/possample.html [www.sidefx.com]
https://procegen.konstantinmagnus.de/ [procegen.konstantinmagnus.de]
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