AM72 I am reporting a bug in which the Unwrap operation does not cut or separate UV islands according to user-selected seams on a polysurface.
UV Unwrap always fails to separate islands at selected seams on this polysurface.
Always using these files,
Rh9 B.3dm (2.4 MB)
Rh9.3dm (3.6 MB)
Rh8.3dm (2.4 MB)
A full-screen recording video is attached to the help web page; the video was sent via Support: https://www.rhino3d.com/upload
name: AM71 SeamsSelection not deviding
Observed behaviour
After seams are selected on the 3D model (visible as continuous yellow seam lines), the Automatic Unwrap produces a UV layout in the UV Editor where islands that should be divided remain merged or incorrectly connected. The cuts indicated by the seams are not applied. The resulting UV map shows tangled or joined geometry across expected boundaries, making independent island editing, packing and texturing impossible.
The attached screen recording demonstrates the complete sequence.
The issue persists across repeated attempts to re-select seams and re-execute Unwrap. Operations involving mapping-channel addition and removal were also performed without resolving the separation failure.
Steps to reproduce
- Open a polysurface model.
- Activate Unwrap, select Texture Mapping (Mapping channel 1).
- Select seams on the 3D object (Chain selection or manual).
- Press Enter to finish the Unwrap command with the Automatic method.
- Inspect the result in the UV Editor.
Expected behaviour
The UV Editor should display cleanly separated islands whose boundaries correspond exactly to the seams chosen by the user. Each island should be independent and ready for further editing or packing.
Actual behaviour
Selected seams are ignored or only partially respected; islands remain merged or improperly joined in UV space.
Additional information
In Rhino 9 Work In Progress
(9.0.26153.12415, 2026-06-02)
Thank you for investigating this issue.