Hair Curve "Invalid UV Map: UV Islands must not overlap" does not take into account multiple materials #117806

New Issue

Dan McLaughlin · 2024-02-04T15:43:00+01:00

Dan McLaughlin commented

2024-02-04 15:43:00 +01:00

System Information
Operating system: Windows-10-10.0.22631-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 546.33

Blender Version
Version: 4.0.2, branch: blender-v4.0-release, commit date: 2023-12-05 07:41, hash: 9be62e85b727

Description of issue
With hair curves UV islands can't overlap, however I'm not sure if that's a fundamental issue or of the system simply is not recognizing that a mesh can have multiple materials. The multi-material system is exactly for this purpose, it allows reusing the UV space to gain more texel density by having different materials use the entire UV. So I'm wondering, why isn't the curve system taking into account overlapping islands within the present material? This is a very common workflow that it seems should be supported, but there may be technicalities such that it cannot account for the material that a island belongs to, but it's not obvious why that would be.

It can be worked around by using UDIM's or multiple UV spaces, but that may not be possible with a workflow. Attached is a blend file with a simple two material object where the two islands overlap.

**System Information** Operating system: Windows-10-10.0.22631-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 546.33 **Blender Version** Version: 4.0.2, branch: blender-v4.0-release, commit date: 2023-12-05 07:41, hash: `9be62e85b727` **Description of issue** With hair curves UV islands can't overlap, however I'm not sure if that's a fundamental issue or of the system simply is not recognizing that a mesh can have multiple materials. The multi-material system is exactly for this purpose, it allows reusing the UV space to gain more texel density by having different materials use the entire UV. So I'm wondering, why isn't the curve system taking into account overlapping islands _within the present material?_ This is a very common workflow that it seems should be supported, but there may be technicalities such that it cannot account for the material that a island belongs to, but it's not obvious why that would be. It can be worked around by using UDIM's or multiple UV spaces, but that may not be possible with a workflow. Attached is a blend file with a simple two material object where the two islands overlap.

HairCurves.blend

1.1 MiB

Dan McLaughlin added the

labels 2024-02-04 15:43:01 +01:00

Iliya Katushenock commented

2024-02-04 15:50:41 +01:00

Thanks for the report, but the issue reported here is a request for modified/improved behavior and not a bug in current behavior. Closing as this bug tracker is only for bugs and errors.

To avoid this, you can separate mesh faces for each material and sample them separately.

For user requests and feedback, please use other channels: https://developer.blender.org/docs/handbook/communication/user_feedback/

For more information on why this isn't considered a bug, visit: https://developer.blender.org/docs/handbook/bug_reports/not_a_bug/

Thanks for the report, but the issue reported here is a request for modified/improved behavior and not a bug in current behavior. Closing as this bug tracker is only for bugs and errors. To avoid this, you can separate mesh faces for each material and sample them separately. For user requests and feedback, please use other channels: https://developer.blender.org/docs/handbook/communication/user_feedback/ For more information on why this isn't considered a bug, visit: https://developer.blender.org/docs/handbook/bug_reports/not_a_bug/

Iliya Katushenock closed this issue

2024-02-04 15:50:43 +01:00

Blender Bot added

and removed

labels 2024-02-04 15:50:45 +01:00

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