Moving UVs in UV Editor produces corrupted UVs on mesh export (OBJ/FBX)

Rhino
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P5 008
P5 0081920×1200 231 KB

AM73

Moving UVs in UV Editor produces corrupted UVs on mesh export (OBJ/FBX)

Rhino Version: Rh 8 SR32 (8.32.26160.13001, 2026-06-09)
Video:

Summary

As shown in the video, and always using this file, UV vertices do not export correctly. OBJ and FBX in this case.

NOT Attached Files (Was included via Rhino Web Form)

  • AM73 Moving UV export bad Start.3dm — Initial model + UV setup ready for edit.
  • AM73 Moving UV export bad Final.3dm — Model after UV move + export/import cycle showing the corruption.

Steps to Reproduce

  1. Open AM73 Moving UV export bad Start.3dm.
  2. Select the mesh object.
  3. Open UV Editor and move/scale/rotate UV islands or specific vertices (exact actions shown in video).
  4. Export the object as OBJ (or FBX) with standard settings (look at Additional Note custom commands).
  5. Import exported file into Blender (or RizomUV in this case). and Inspect the UV map.

Expected

UVs must be identical to the final edited state.

Actual

UV layout in the exported file is corrupted: vertices jump to random positions, texture mapping breaks. The “Final” and “Special” files demonstrate the broken state (of the model UVs) after the export round-trip.

Impact

  • Critical for any workflow
  • No workaround

Additional Note

  • The ! _ExtractRenderMesh command was used

  • I go back and forward using RizomUV RealSpace

  • Eport commands:
    ! -_Export
    _SaveTextures=_No
    _SaveNotes=_No
    _SaveSmall=_Yes
    _GeometryOnly=_Yes
    “…path\UVmesh.obj”
    SubDLevel=5 VertexWelding=Welded YUp=Yes enter enter

  • Jussi, since Rhino does not export welded surfaces UVs, to get the island, I make a Welding by proximity inside RizomUV. So, in this way, in Rizom, I’m able to work as in Rhino, selecting the islands.

  • But minimum interaction between the two because it triggers bugs.

  • Import commands:
    ! -_Import
    “…path\UVmesh.obj”
    enter enter

  • The file is too big for just a mesh of a few points.

  • Reducing the file size as much as possible in this included special file:
    AM73 Special File.3dm (449.0 KB)
    Notice that the UV Editor is different from the exported OBJ one.

  • Same issue if exported as FBX.

[AI generated text :] Proposed Next Steps for McNeel

  1. Verify UV Editor state is fully written back to mesh before any export or meshing operation.
  2. Add internal consistency check or “bake UVs” command that forces synchronization.
  3. Regression test with complex multi-island UV layouts + move operations + OBJ/FBX export.
2

RH-96709 moving uvs in uv editor causes corruption

@Jussi_Aaltonen will have to take a peek at this-