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Mesh Subdivide with smoothness is coordinate dependent
Closed, ArchivedPublic

Description

System Information
Windows 7 Professional 64-bit service pack 1
Intel Core i7-2600
8GB RAM
NVIDIA GTX 1060 6GB

Blender Version
Broken:
2.79b f4dc9f9d68b
2.80 Alpha 2 db1a04313c3

Short description of error
Mesh Subdivide with smoothness is coordinate dependent although it shouldn't be.

Exact steps for others to reproduce the error
Apply mesh subdivide with smoothness > 0 and high enough number of cuts.
Proper result is all meshes to be have identical shape but actually they all be differently.

Note: I cannot judge whether this issue is caused by same reason as T57103 or not, so i decided to report this separately.

Details

Type
Bug

Event Timeline

Philipp Oeser (lichtwerk) triaged this task as Confirmed, Medium priority.

Can confirm this (although I am not sure this is solvable easily)
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Subdivide smooth depends on vertex normals. These are mostly fine when having meshes with faces but are more "problematic" in edge-only meshes.
(you can inspect these with the Normals Overlay)

So as a workaround you could extrude the edges just a little in Z (note how the normals are much more "predictable" now), subdivide smooth then, and get rid of the extra edgeloop afterwards.

I would have to dig a little deeper on how blender actually calculates normals for edge-only meshes (not sure if this be improved even theoretically).
Or think about another workaround.

maybe @Campbell Barton (campbellbarton) can comment?

Confirming/Claiming for now (so it doesnt get lost)

Philipp Oeser (lichtwerk) closed this task as Archived.Fri, Feb 1, 11:11 PM

So while this would be nice to support, it is not a bug - I'll quote from another report here:

Taking into account vertex normals for vertices and edges could be useful, but that's a missing feature that would be nice to add, not a bug.

Will archive this then...