UnrollSrf and Smash still not able to keep Mapping coordinates

Hi Folks,
I’m trying to unfold a simple shape (Polysrf) while retaining the Uv coordinates from the shape to the flatten version.

I’ve already found some good workaround here in the discourse but it’s not satisfying.

Unroll and Smash of a polysurface can’t keep the UV coordinates like expected.
This issue is really old and looks like many of us need this.

See this threads:
Unroll texture on a tube surface with into flat surface
unroll 3d model with texture
unwrapping a uv mapped sphere to print 2d graphic

Maybe @Gijs @Vanessa and @Jussi_Aaltonen could you support this thread?


Hello- does UnrollSrfUV do what you need?

Hi Pascal,
Nope. :frowning:

Hi Riccardo - What happens if you assign the same material to the unrolled faces as is on the input? This is not inherited automatically. Probably should be…


This is already the “baked” material.
If you look closely to the upper corner you’ll see the black tip.
The White Is the white part of the map heavily stretched.

In my opinion when the unrollsrf/smash happen it should unroll/smash also the underlying mesh and use it to apply the correct UV mapping to the flat result. Would it be possible?

Hi Riccardo - I see - so the material is not UV mapped, correct? The object uses some other mapping?


Hi Pascal,
Thanks for the Sunday support.

The problem happens no matter the mapping.
What I did is to map the shape as cylindrical map, then bake it to retain the image shape onto the polysrf and then unroll/smash the polysrf.
The flatten version is correctly keeping the baked material but with surface uv mapping instead of keeping the original UV.
The result is then the entire baked map is stretched on each piece.

I’ll upload an example later today.

Hi skysurfer,

Please note that the topic of the same subject is already opened, you can access it in this link:

The Rhinoceros team has been working hard to resolve this issue since 2014. I think I read somewhere they pick specific user-reported broken feature issues only once in a few years to not slow down working on new features. This is because the business development team says the new feature sell not a working feature!
I can’t wait for them to start working on this issue.

Hi Riccardo - an example would be good - here this seems to work OK in my simple test.

BakedUnrollSrfUV.3dm (123.4 KB)



@pascal, @BrianJ
here the file Rhino_Smash.zip (5.1 MB)
I made (V7 but V8 is the same) to try the Smash of a baked geometry.

To me it looks like after the smashing an unpacking/reset of the uv coordinate is done on the flatten srf.

Any idea? I client would need this function so much.


Hi Riccardo - I see… what I don’t yet see is why my test bake of a spherically mapped surface makes a full image

and baking from your model even with different mapping from your custom object, is only making a ‘partial’ image


You can get something to look better using the UVEditor but it amounts to lowering the resolution by a lot


but I don’t know how to tell when it is right.

Still poking.
RH-79787 Baking makes partial image

@skysurfer for now this workaround might help you forward:
Reparametrize (automatic) the surface

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I’ll give it a try and I’ll back to you.

Thanks @Gijs , and @pascal

@skysurfer my suggested workaround might lead to different mapping results according to @Jussi_Aaltonen so be careful to check the results if you decide to go that route.

See also




Hi @Gijs,
Thanks for the added information.
Just for you convenience I can’t access the second YT link (probably isn’t pubblic).

@Jussi_Aaltonen I read the YT RH-79787 comment and I agree that the problem is into the Unroll/smash resetting the UV coordinates during the flattening process. With the KeepProperties=Yes I’m expecting the command to “Keep” the texture as well.

Thanks to all,


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@skysurfer - I hope all is well ;-)!
I’ve logged these two:
RH-79810 Smash should keep texture mapping
RH-79809 UnrollSrf should keep texture mapping

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Hi @Vanessa, could you please add _Squish to this list as well ?


There are currently some issues in how the surface parameter information of the Nurbs geometry is stored in the render meshes. I have fixed one bug (RH-79840) today and will investigate further what has been changed since Rhino 7.

Another work around in addition to Reparametrize is to run ClearAllMeshes and switch back to Rendered display mode. That re-creates all the render meshes for those surfaces. As far as I can tell after that Bake and Smash work as in Rhino 7.

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Hi @clement - Yes, of course: RH-80276 Squish should keep texture mapping.

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