SLIM UV Unwrapping

This is strange english I think. Smooth and Sharp are adjectives.
At least it should be ‘Unwrap by Smoothness’. But that sounds strange to me and I would have no idea what it would mean.

I’d prefer :

‘Unwrap Preserving Angles’ (for angle based)
‘Unwrap Minimizing Stretch’ (for SLIM)

As those
a) both start with ‘Unwrap’
b) clearly describe the desired outcome.


I was trying to come up with something like this. Makes more sense, it’s proper english and is clear enough (the name of the method itself doesn’t have to appear in the interface, I guess, or perhaps just in the tooltip)

I’ve pushed some improvements to the triangle correction function in the PR and now SLIM unwraps that mesh when unwrapping from the 3D viewport, but fails to unwrap when unwrapping from the UV editor.

Didn’t have time to check what’s the reason of this inconsistency yet.


The build has been updated with the latest changes (same link as before):


Hi guys. Unfortunately I am not able to reproduce the issue with pins. Probably it’s only visible in a specific situation. Could you provide a minimal blend file allowing to reproduce the issue?


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Ok, nevermind. I think I figured it out - it looks like the issue is present only when the number of iterations is set to 1. It will debug the issue and let you know soon.

[EDIT]: Build with pins fixed can be downloaded here: Blender Builds -


@glukoz ill try to do some testing during the week.
Is there any particular situation that need more testing than other?


Thank you. I cannot think about any specific situation. Only a general idea applies: the more complex mesh, the more it’s worth testing I guess. Also remember to try it with pins :slight_smile:

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Hi, i have been testing a bit more using the build above it work beatifully most of the time, the main issue i found was with knowing in the uv editor, when was SLIM working and when it was just stop, didn’t get any crash but several times meshes collapsed when i was trying to force weird position others simply by scaling some pinned point (see NB1 bellow)
PIned feedback.MP4 - Google Drive (Couldn’t upload this video here, sorry)

In this Drive link are the blend files with the meshes to test i used.

NB1: This is something that i saw several times, the simulation simply colapses into the corner

NB2: In the video mentioned the bug happen if there are inverted normals, after keep testing other meshes i find out that the bug its just in the group field, add a randon name of no group there and it glitches SLIM

NB3: This was an unexpected result, in this example in particular slim with vertex pinned and live unwrap in the uv editor work as expected, the normal unwrap with slim didn’t


I have tested the new SLIM Unwrap on a wide range of meshes, and it seems to work really well in all cases I tried so far! Any news on when it will be merged? Really looking forward to this one :slight_smile:


This implementation still needs some polishing (as indicated by great feedback by @NahuelBelich - see above). I am currently working on issues pointed by him.


just test it todays build that Brecht push to buildbot.
It does work much more stable than the last one, i wasn’t able to make SLIM collapse the uv :+1:


Thank you for feedback and testing.

For others info: the latest SLIM build can be download from here: Blender Builds -