[BUG] To be able to _WeldVertices of a mesh converted from SubD you need to export and import as OBJ

Rhino SubD
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1

_WeldVertices was not working.

Sometimes when you try to weld vertices of a mesh and they do not weld,
as shown in this video (subd extracted mesh)

________________________________________ OLD

using Rhin6 (Not Rhino7 WIP)
In Rhino 7 WIP the OBJ export is broken.

In this video, I convert a SubD to mesh or extractRendermesh (is the same).
I make two comply. The one in the middle I export it as OBJ and reimport it.
Then I apply _WeldVertices to both meshes. (I will lose UV mapping but is fine in this case)
As shown at the end of the video, the exported one was able to weld vertices
By default, WeldVertices is not welding.
So you need to export as OBJ and reimport it to make it work.
Side note
Mesh welding is necessary to reduce draw calls or for having a unique UVmapping with no island so that is possible to apply UV mapping outside. Mesh welding in Rhino is important because it preserves vertex normals.

2

Can you provide the macros and the 3dm please? I’ll make sure it is filed as a bug if needed.

3

Yes I have done that inside the bug report:
https://mcneel.myjetbrains.com/youtrack/issue/RH-58199

SOLUTION
In Rh6, export the mesh as OBJ and Import it.
Now try again to weld with the imported ones.
Often that fix the problem

The starting mesh was invalid,
But exporting as OBJ and reporting it fixed that problem
At the end of the video, I try to fix the invalid surface.