Texture image wrong after weld

I have a mesh from a scanning device. When I unweld it and later weld it again the texture does not fully cover the object anymore. Is there a workaround for this?

HI Aad - I think you want weld at something larger than zero - I’m not sure what weld at zero gets you.


If I weld and unweld with 15 degrees I get similar results

Hi spitstec - can you post the file and texture, or send to tech@mcneel.com? I’ll take a look.

@spitstec - Hi Aad - try this:

Duplicate the object, hide the copy.
Unweld-Weld as needed.
Show the copy.
Select the welded/unwelded object and in Properties > Mapping, choose ‘Custom mapping’ (rubber duck icon). Choose the copy that you just showed as the mapping object. You can hide or delete the object once its texture coordinated have been mapped onto the unwelded object.

Does that do it?
Hm apparently not… Still poking…


If I remember me right I reported it in the past too. I would be very happy if this could be fixed, from time to time I run in this problem. My solution is to use Ultimate Unwrap 3D for this task. Could be great to stay in Rhino.

as far as i understand the UV topology and the actual mesh topology have to be the same. It means that every UV-patch is also an unwelded seam in the original mesh. Once you weld them, the UV - topo changes as well.

As for the why: every Mesh-Vertex in Rhino can only have ‘one’ UV coordinate, while in reality it would need more than that.

That seems to be a general limitation of Rhino?

I now found a workaround for this. This works when only one single material is involved.

  1. Export the meshes to an obj file
  2. Edit the obj file with notepad: replace lines that start with “usemtl” by ";usemtl"
    replace all except the first “usemtl” line
  3. in rhino delete the meshes and import the obj file

It remember me on an old problem. So far I understand there are different ways to handle meshes and the Rhino system is quite limited. Some years before Michael from MoI3D explained it at post no 3 of this thread:

I don’t know so much about this topic but maybe the old thread helps someone to find a way to change the handling of mesh data at Rhino. The old thread is about shading normals at welded edges, but I think it’s the same problem for UV coordinates at edges. Could the mesh system not be changed for Rhino 6?