Hello, I would like to report 2 issues in Rhino 6.
As you can see in this video “Previous Seams Selection” seems to have some issues. It makes a selection of some apparently random edges, that are not those being chosen. Over and over.
It was working correctly in v.5
The other problem is that welding a mesh seems to lead to incorrect UV projection. This used to happen in v.5 too. Even if unwrapped after welding.
I’m not seeing this here using Rhino 6.13 which will soon be the next service release, can you post the 3dm you used in the video please? I believe the issue is https://mcneel.myjetbrains.com/youtrack/issue/RH-43492 which was fixed for 6.13. I can test your file or you can choose ‘service release candidates’ from Options>Updates and Statistics>Update Frequency, then click ‘check now’.
I believe this is https://mcneel.myjetbrains.com/youtrack/issue/RH-45510 which is still an open bug. I found a manual fix listed on the bug report that may help in the meantime…
Use the command UnweldVertex
Drag a fence selection over your mesh to select all the vertices>Enter
Run the Explode command on the mesh
Run Join on the mesh
If that fixes the issue for your mesh, please let me know and I’ll add this thread to the bug report. If you can upload the 3dm you used in a state that shows the issue that would help too. I reproduced it here copying your form and the manual fix worked without destroying the UVs.
Thanks Brian I’m glad it’s already been fixed. 
If it still could be of any help, here is the 3DM file.
Regarding the ‘welding issue’… i followed the instructions and the mesh gets repaired indeed but also unwelded.
What I was looking forward to achieve was -in the perspective to import it in UnrealEngine- the possibility to use “welding” on certain parts of a mesh to fake-smooth geometry like 3DS “smoothing groups” does.
I heard this is the suggested method… but if welding “damages” UV it’s a problem…
Thanks, prev edge selection is working on your model in 6.13 here as well.
The UVs were preserved in the Rhino UV editor after UnweldVertex, are they not transferring to Unreal after that or is the issue that the smooth shading gets lost there? Have you also brought the model over to Unreal already as a test when the texture is getting stretched due to the vertex welding in Rhino’s Rendered display mode? I’m wondering if Unreal will have the same issue or if it is just Rhino’s Rendered mode.
Actually I never imported a mesh with apparently broken uv…
I’m leaving home right now but I’m going to test it soon and update this topic with the results.
Okay thanks, let me know what you find. The UV’s are not broken as far as I can tell, it’s just that Rhino’s Rendered display isn’t displaying the texture map correctly. It might just be a Rhino display issue and hopefully that bug above can be looked into soon.
Ok, I did some tests and that’s what comes out
I hope it can be of any use to go through this issue.
Rhino v.6.12.19029.6381
Exported as: OBJ
Test Mesh weld UV.7z (8.8 MB)
I have the same issue, in Rhino7. I wonder if they will ever going to fix it.
It is almost like sabotaging possibility of using rhino for game engines.
UV Mapping / unwrapping / etc are getting some good improvements in v8
