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Subdivision Surface Modifier (Simple) on faceless corner acts like Catmull-Clark
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Description

System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 970/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.86

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-23 13:52, hash: rBb63f0266a056
Worked: (optional)

Short description of error
When Subdivision Surface Modifier (Simple Type) is added on faceless edge corner,
The mesh is smoothed as if Catmull-Clark Type.
This is not the way 2.79 was.
I have captured a screenshot for both versions below.

Exact steps for others to reproduce the error
Add plane and then edit the plane.
Delete the face by Delete Only Faces. Four vertices and faceless edges remain.
Add Subdivision Surface Modifier and set it to Simple Type.
The mesh is smoothed as if Catmull-Clark Type.

Though it looks that the difference have little meanings since faceless edges are not rendered,
some modifiers (Skin Modifier for example) can depend on the shape of faceless edges,
This difference can cause some trouble when importing models from 2.79.

Event Timeline

Germano Cavalcante (mano-wii) triaged this task as Confirmed, Medium priority.

I can confirm, subdivision of the Simple type to loose edges does not have the expected effect.

I appreciate quick fixing.
I have tried with new build at date: 2019-07-25 14:34
I found that simple subdivision surface still behaves strangely on loose edges.

Attached image is a suzanne with all faces removed (only loose edges) with simple subdivision surface.


It looks that z-components of subdivided vertices are set to be 0.
Only x and y components are subdivided properly, I guess.

Actually the ideal is to make another report.
But @Sergey Sharybin (sergey), can you have a look at that problem described in the comment?

@takaaki takeda (popqjp), please make a new report, is better this way.

Also, is it only affecting Simple subdivisions or Catmull-Clark as well?

O.K. I will make a new report.
It is affecting Simple subdivisions only.
Catmull-Clark looks good.