Editing object with UVs and SubSurf is very slow. #54559

New Issue

Vadik · 2018-04-10T16:48:45+02:00

Vadik commented

2018-04-10 16:48:45 +02:00

System Information
Windows 10, different i7, 560ti, 1060

Blender Version
Broken: 2.78, 2.79

Short description of error
Editing object with UVs and SubSurf on is very slow.

Exact steps for others to reproduce the error
Create object, subdivide couple of times, add SubSurf, add 2-3 UVs, try to edit - very slow.
Without UVs everything is fine.
Attached file - try to edit one and another object, feel the difference.
bug_Uv_edit_mesh.blend

**System Information** Windows 10, different i7, 560ti, 1060 **Blender Version** Broken: 2.78, 2.79 **Short description of error** Editing object with UVs and SubSurf on is very slow. **Exact steps for others to reproduce the error** Create object, subdivide couple of times, add SubSurf, add 2-3 UVs, try to edit - very slow. Without UVs everything is fine. Attached file - try to edit one and another object, feel the difference. [bug_Uv_edit_mesh.blend](https://archive.blender.org/developer/F2653560/bug_Uv_edit_mesh.blend)

Vadik commented

2018-04-10 16:48:45 +02:00

Added subscriber: @sid350

Philipp Oeser commented

2018-04-12 13:54:35 +02:00

Added subscribers: @Sergey, @lichtwerk

Sergey Sharybin was assigned by Philipp Oeser

2018-04-12 13:54:35 +02:00

Philipp Oeser commented

2018-04-12 13:54:35 +02:00

I think this is intended behaviour.

Not very familiar with the subsurf code, but here is my explanation:
Once the input mesh is edited, subsurf will always end up calling CustomData_interp (and thus UVs of every single layer are interpolated for the derrivedMesh -- which is where blender spends most of the time calculating)
While they might be some operations (like moving a vertex - which is not altering UVs) where a something like a reusable cache is thinkable?, there are others where interpolating is absolutely neccessary (vertex slide with correct UVs, or just moving a UV itself). That being said, I dont think subsurf can make a distinction if you move a vertex or a UV, its just always doing its thing. Don't think this is a bug.

Stopping this uneducated blathering, I'll kindly ask @Sergey to share his wisdom

I think this is intended behaviour. Not very familiar with the subsurf code, but here is my explanation: Once the input mesh is edited, subsurf will always end up calling `CustomData_interp` (and thus UVs of every single layer are interpolated for the derrivedMesh -- which is where blender spends most of the time calculating) While they might be some operations (like moving a vertex - which is not altering UVs) where a something like a reusable cache is thinkable?, there are others where interpolating is absolutely neccessary (vertex slide with correct UVs, or just moving a UV itself). That being said, I dont think subsurf can make a distinction if you move a vertex or a UV, its just always doing its thing. Don't think this is a bug. Stopping this uneducated blathering, I'll kindly ask @Sergey to share his wisdom

Vadik commented

2018-04-13 15:30:01 +02:00

It's just becoming a bit frustrating to edit rather complex mesh if it has even 1 UV on it. Need or remove UV or turn off subsurf, which is necessary sometimes. Maybe it doesn't need to recalculate UVs depending on subsurf in real time when you move vertex, if it's not a 'Texture' view.

Sergey Sharybin commented

2018-04-24 13:05:17 +02:00

Changed status from 'Open' to: 'Archived'

Sergey Sharybin closed this issue

2018-04-24 13:05:17 +02:00

Sergey Sharybin commented

2018-04-24 13:05:17 +02:00

Here it is up to the subsurf modifier to update UVs, and transform code just pokes object to update subsurf (since vertex location has changed). There is no simple solution here, since modifier stack can not re-use UVs even if they did not change.

So thanks for the report, but it's more an optimization request than a real bug :)

Here it is up to the subsurf modifier to update UVs, and transform code just pokes object to update subsurf (since vertex location has changed). There is no simple solution here, since modifier stack can not re-use UVs even if they did not change. So thanks for the report, but it's more an optimization request than a real bug :)

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Editing object with UVs and SubSurf is very slow. #54559