Hair Curves: Invalid surface UV attachment #110706

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SleepyEngi · 2023-08-02T00:21:15+02:00

SleepyEngi commented

2023-08-02 00:21:15 +02:00

System Information
Operating system: Windows 10
Graphics card: Nvidia RTX 2060 Super

Blender Version
Broken: 3.6.1
Worked: N/A

Short description of error
When using 'Interpolate Hair Curves' and 'Deform Curves on Surface', a small amount of curves can appear that have a "Invalid surface UV attachment", causing these curves to be unable to pose. They are left as floating particles which is a big issue for final renders with posed characters/objects.
Furthermore, if the surface mesh is subdivided, more curves appear that do not pose with the mesh correctly and instead stay in rest position, however these are not considered an "invalid surface UV attachment", and thus cannot be removed with the 'hair attachment info' node's selection. There is no way to clear these "valid" invalid curves, they stay floating.

Exact steps for others to reproduce the error
Based on the default startup or an attached .blend file (as simple as possible).

The provided file contains a posed mesh, moved slightly to the right, to show that one particle is left floating in the air.
Open the provided file, and render the image.

The problem should appear in the render as a single floating particle.
Now check the geometry nodes setup and see that we have deleted the supposedly invalid curves, but one remains yet floating in the air far from the posed mesh.

Notes about the file

A simple small surface, posed with an armature slightly to the right to show that some curves are not moving with the mesh correctly
A regular UV map made with smart uv pack, no overlaps, udims or islands outside the bounds.
The hair curves object was made by converting a hair particle system object to curves, and then used "snap to nearest surface" on hair sculpt mode to attach it to the surface
Which hairs are bugged depends on the 'intepolate hair curves' node's seed, for example on seed 2 this "valid" invalid curve appears, but not on some other seeds, and more appear on other seeds, completely randomly

Further notes after experimenting

I suspect this is related to seams, as the problem seems to happen more often close to seams on the subdivided mesh, and better UV maps result in the bug happening less, but still happening. I added more seams to the simple mesh in hopes of the bug appearing more often.
Problem seems to happen more often if you use the boundary smooth option on the subdivision modifier; still happens if option is disabled but less.

**System Information** Operating system: Windows 10 Graphics card: Nvidia RTX 2060 Super **Blender Version** Broken: 3.6.1 Worked: N/A **Short description of error** When using 'Interpolate Hair Curves' and 'Deform Curves on Surface', a small amount of curves can appear that have a "Invalid surface UV attachment", causing these curves to be unable to pose. They are left as floating particles which is a big issue for final renders with posed characters/objects. Furthermore, if the surface mesh is subdivided, more curves appear that do not pose with the mesh correctly and instead stay in rest position, however these are not considered an "invalid surface UV attachment", and thus cannot be removed with the 'hair attachment info' node's selection. There is no way to clear these "valid" invalid curves, they stay floating. **Exact steps for others to reproduce the error** Based on the default startup or an attached .blend file (as simple as possible). - The provided file contains a posed mesh, moved slightly to the right, to show that one particle is left floating in the air. - Open the provided file, and render the image. The problem should appear in the render as a single floating particle. Now check the geometry nodes setup and see that we have deleted the supposedly invalid curves, but one remains yet floating in the air far from the posed mesh. **Notes about the file** - A simple small surface, posed with an armature slightly to the right to show that some curves are not moving with the mesh correctly - A regular UV map made with smart uv pack, no overlaps, udims or islands outside the bounds. - The hair curves object was made by converting a hair particle system object to curves, and then used "snap to nearest surface" on hair sculpt mode to attach it to the surface - Which hairs are bugged depends on the 'intepolate hair curves' node's seed, for example on seed 2 this "valid" invalid curve appears, but not on some other seeds, and more appear on other seeds, completely randomly **Further notes after experimenting** - I suspect this is related to seams, as the problem seems to happen more often close to seams on the subdivided mesh, and better UV maps result in the bug happening less, but still happening. I added more seams to the simple mesh in hopes of the bug appearing more often. - Problem seems to happen more often if you use the boundary smooth option on the subdivision modifier; still happens if option is disabled but less.

ValidCurveBug.PNG

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ValidCurveBug3.PNG

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ValidCurveBug2.PNG

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Hair Bug Report.blend

4.2 MiB