UVEditor & ExtractUVMesh bug?

@Jussi_Aaltonen, @DavidEranen,

in the last decade i’ve been using my own scripts to unwrap UVs of 3D meshes which worked fine. Recently i’ve developed a tool to remap objects from a 2D mesh (created by UV unwrapping) onto a 3D mesh. While testing this out i’ve found that sometimes the face count, vertex count and almost always the vertex ordering per face is changed by Rhino’s _UVEditor and _ExtractUVMesh commands. This is especially problematic if i rely on the topology of the meshes to remap from / to.

Attached is a very simple example where i can repeat that behaviour. I’ve numerized the first 4 vertices. After unwrapping the cylinder using _ExtractUVMesh , the face and vertex count properly matches. However, the vertex order is not preserved. The 2D mesh has the following vertices for the first face:

2D Mesh: FaceIndex: 0 >>> 0,1,2,3

while the 3D mesh gives me these vertices:

3D Mesh: FaceIndex: 0 >>> 0,99,101,9

Is this expected ? I get the same results in Rhino 5 but i am not sure if this is correct. If i use one of my own unwrappers which creates a 1:1 swap between texture coordinates and vertex positions, the face vertex ordering is 100% identical.

Cylinder_FaceVertexOrder.3dm (100.2 KB)


As a follow up to the above mentioned commands:

  1. If a mesh is triangulated on purpose and the command _ExtractUVMesh is used, the resulting extracted mesh is made up of quadrangles only. It would be useful to have an option to Extract the UV-Mesh without changing it.

  2. If a unwrapped mesh is shown while using the _UVEditor and the dialog is open, please save and close the document. After reopening the document, the dialog is not shown and the unwrapped mesh looks like a regular mesh, it is still visible. Only if the _UVEditor is started again and after using ESC when it prompts for a rectangle and canceling the dialog, the unwrapped mesh(es) disappear.


Hi @clement,

Thanks for writing this up. I was able to reproduce the first two bugs, but the third I was not able to reproduce (UVEditor dialog not shown when re-opening and unwrapped mesh looks like regular mesh).

I created these YT items:

Could you try to explain in more detail how to reproduce the UVEditor dialog bug? For me, the dialog was up (but docked to Rhino) when I opened the saved file. I’m testing this in V6.


Hi @DavidEranen, i’ll send something via PM which shows the case.

thanks for logging the issues.


@DavidEranen, below are some steps to reproduce another serious bug with the UVEditor:

  1. Create a NURBS Box, use _Unwrap, select all edges of the Box, Enter
  2. Start the _UVEditor, create a rectangle, Apply
  3. Explode the Box, delete all faces but one
  4. Start the _UVEditor again, create rectangle

Why are all 6 faces shown here when i’ve deleted 5 of them ?


Thanks @clement,

Reported: https://mcneel.myjetbrains.com/youtrack/issue/RH-47962