V6 - change in how UV mapping works

I’ve been doing some UV mapping lately and have noticed a change in how Rhino deals with previously UV mapped surfaces in the UV editor.

My workflow has been -

  1. Unwrap surfaces and select seams.
  2. Open UV editor to the exact scale of the texture I’m going to apply (let’s say 200mm x 200mm).
  3. Measure distance of a known feature of geometry and then scale the UV mesh to the correct scale.
  4. Close the UV editor.

Then, if I need to go back in and edit anything I would just re-open the editor at 200mm x 200mm and the mesh would be there at the scale I left it.

Now what happens is - when I re-open the UV editor it has scaled the mesh to fit the UV texture space which upsets my workflow a little and makes it very hard to re-discover what size texture you applied to the surfaces.

Is there any major advantage to this change or could we have the old behaviour back? Or is there a better way to find out what real-world scale has been applied to the texture of UV mapped surfaces?



Some pics below-

Here’s how I create the mapping and would also expect to see it when re-opened in the UV editor -

And here’s how it looks when I re-open it in the UV editor -

Indeed i tested myself its weird behavior since if any of external renderers supports udims it will mess up stuff totally. Leaving the link to some udim explanation and source to additional places about udims.


@Jussi_Aaltonen do you know something about it? Is this expected behavior? I could be missing something that could be a potential advantage of this new approach.

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Hi @mcvltd, can you remember when this behavior was changed?

This might be the reason for this change in behavior:
RH-35013 UVeditor: Does not display wcs projected textures correctly


Unfortunately not, I’ve been away from Rhino for about 2 years…

So would it help if there was a setting Fit UV meshes to unit range (Yes/No)?

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If that meant I could get the old behaviour back then yes, absolutely!

Could it be sticky, so that what ever option I chose prevailed until I needed to change it?

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Yes, it should be made sticky. I filed it for Rhino 7:
RH-53811 UVEditor: Setting to toggle fitting of UV meshes to UV rectangle