I’m struggling with strange issue i cannot unwrap bottom part of this object - for some reason bottom part is always sticked to rest of the the model i tried everal times to select seams at the end i decided to select all possible edges to split uv islands apart but it seems that there are verticies that are sticked forever 
Any clue on this ?
Here is the model (i saved small - cause it happened on every custom mesh for me):
no_unwrap.3dm (257.3 KB)
What I get when opening your file is not what shows on your posting shot. There is a simple closed polysrf. Exploding it yields 21 normal surfaces, some are trimmed. Nothing strange or abnormal.
@ChrisK did u read title? I have issue while running uv unwrap of this ‘simple’ closed polysrf with almost all in g2 on top. When i try select seams and map texture with smallest distortion on it i cant cause i’m getting forever sticked render meshes no matter how i will select seams.
I never heard of unwrap. What does it do?
@ChrisK check this video https://youtu.be/75cQX-iF8YA
Thank you. I’ve not given much attention to rendering. Perhaps now I shall. 
@D-W,
unwrapping requires that the parameterisation of your surfaces are good. I did some changes to your polysurface:
_Explode
_ShrinkTrimmedSrf
_Reparameterize _Automatic
_RemoveFlippedNormals
_Join
then i used _Unwrap and selected some of the logical edges. Once the command was done i used the _UVEditor to lay out the UV islands. The scaling or nesting algorithm used is not optimal, so this has to be done by hand.
unwrap.3dm (443.5 KB)
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@clement i’ve done the same and result is still same (with joined verex on render mesh) 
I know that i need to layout on my own cause rhino auto stuff is bit messy - but i dont get why i still get joined vertecies
btw. i dont have _RemoveFlippedNormals ? latest sr on v5 ? it isnt listed at all but seems its working 
@D-W, this is what i get if i run the UVEditor on my file posted above in Rhino 5:
How are you picking the edges ? By single pick or window selection ?
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@clement in your file everything works perfect i just tried to run all those commands on my file but i get same result as earlier hmm by window i also tried to chain select bottom and rest by hand. Did u select all of them by hand?
Yes, by picking the edges manually. For the commands i used before, the order matters. I used this macro:
_Select _Pause
_NoEcho
_Explode
_ShrinkTrimmedSrf
_Reparameterize 0 1 0 1
_RemoveFlippedNormals
_Join
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@clement i used your macro and i still get sticked verts this time it looks like that
Maybe @pascal @nathanletwory @andy ? Any ideas why this is happening? What i should be aware of to prevent this behaviour?
@D-W, when i _ClearAllMeshes then use these custom mesh settings for the object:
then start the _Unwrap command and window select all edges, then wait, i get this without using above macro:
i am using Rhino 5 SR12.
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I’m using Version 5 SR14 64-bit
(5.14.522.8390, 22.05.2017)
Clement please try to unwrap this shape only via bottom edge or bottom plus front concave - when i try this i get:
or
my issue here is bottom part i want to split it somehow in “half” and i always get sticked bottom part look i have this seams selected
When i try do this that way
i get same issue
After exploding merging edges and using your macro leaving default render mesh
Btw. no one from staff can’t say a word on this?
@D-W have you tried unwrapping in BETA? There have been numerous fixes made to unwrapping - V6 will be the next release, no SRs for V5 anymore…
No i didn’t tried cause my render engine of choice isn’t yet released for v6 but as i assume i can copy paste from beta to v5 without issues ?
I think UV unwrapping would save properly. I haven’t tested, but I think it wouldn’t hurt to find out (:
I think you’re giving the unwrapper a hard job because unwrapping the whole shape in one piece would mean you have to compress the whole inner mesh a lot to get it flat. That is something LSCM is not made for and therefore it looks ugly.
You might try below file, i’ve removed the planar bottom just to demonstrate how ABF (angle based flattening) would handle this. To look at it, use the _UVEditor on the mesh. To assign that mapping to the polysurface, select it first then use a custom mapping type (the rubber ducky icon). Once it asks for a custom mapping object, select the mesh.
You can later delete the mesh and change the meshing parameters of the polysurface without destruction of the mapping.
unwrap_cg.3dm (4.3 MB)
@DavidEranen, could you please add ABF to Rhino ? 
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I don’t think ABF is in the works but @Jussi_Aaltonen might know more.
