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Data Transfer modifier not showing transferred uvs in editmode (when the "on_cage" modifier option is used)
Closed, ResolvedPublicBUG

Description

System Information
Operating system: Linux-5.7.10-201.fc32.x86_64-x86_64-with-fedora-32-Thirty_Two 64 Bits
Graphics card: GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 440.100

Blender Version
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-08-04 10:59, hash: rBd6762bedee6f
Worked: deaff945d0b9^
Caused by rBdeaff945d0b9: Mesh: skip conversion from edit-mesh to mesh in edit-mode

Short description of error
Data Transfer modifier not showing transferred uvs in editmode (when the "on_cage" modifier option is used).
I am not entirely sure what the usage of this option is in regards to the Data Transfer modifier tbh, just pointing out that behavior changed in rBdeaff945d0b9.
I think this is a bug, it should just show the transferred UVs if the show_in_editmode option is used?

Exact steps for others to reproduce the error

  • Open file
  • dst object has its UVs transferred from src object, is in editmode and has the modifiers show_in_editmode enabled
  • however, the show_on_cage modifier option is also enabled (effectively now we see the original UVs)
  • disable the show_on_cage modifier option (now showing the transferred UVs -- think this should still be the case with show_on_cage enabled?)
  • alternatively: leave editmode (this will also show the transferred UVs correctly)

Spotted while looking into T79496.

Event Timeline

Note: Whats really cool though [dont think this is a side-effect of rBdeaff945d0b9 though] is that you can now actually see the transferred UVs in the UVEditor with show_in_editmode enabled :)

Pffff.... Spend some hours already trying to understand what happens here, to no avail so far. Am kind of running out of ideas to check in modifier stack itself, afaict everything is fine there.

Issue happens only if DataTransfer is the only modifier in the stack it seems (any other, deforming or constructive, will 'fix' it) Only multi-modifier case still exhibiting the issue is when only 'edit' modifiers are in the stack.

So, this issue happens when both cage mesh and final mesh are the same. @Clément Foucault (fclem) @Jeroen Bakker (jbakker) I see quite some drawing code that checks if those two are identical, so wondering if the problem is not in the logic there actually? Or could it be caused by those final mesh still having the edit_bmesh data?

Bastien Montagne (mont29) triaged this task as High priority.Aug 6 2020, 3:24 PM
Bastien Montagne (mont29) changed the subtype of this task from "Report" to "Bug".
Bastien Montagne (mont29) moved this task from Backlog to Blender 2.91 on the Modeling board.
Bastien Montagne (mont29) edited projects, added BF Blender (2.90); removed BF Blender.