Alembic: import & export face-varying normals
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Authored by Sybren A. Stüvel (sybren) on Jul 5 2019, 1:53 PM.

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Bastien Montagne (mont29)
Sergey Sharybin (sergey)

Commits

rBe9c149d911c2: Alembic import: load face-varying normals

Summary

Loop normals are called 'Face-varying normals' in Alembic. Before this commit, the existence of such normals was used to enable smooth shading. This is incorrect, as the normals could encode flat faces just as well.

This commit adds the loading of these normals as custom loop normals. It then also enables Auto-Smoothing on the mesh (which is a bit of a misnomer and indicates to Blender that the custom normals should be used).

Fixes the glitching described in T65959 and bad normals in T61375.

This introduces a new feature and changes the interpretation of certain properties in Alembic, so definitely aimed for after the 2.80 release.

Diff Detail

Repository: rB Blender

Event Timeline

Sybren A. Stüvel (sybren) created this revision.Jul 5 2019, 1:53 PM

Harbormaster completed remote builds in B3978: Diff 16215.Jul 5 2019, 1:53 PM

From quick look this seems OK…

Regarding whether to include this in 2.80 or later, well, it mostly depends on how safe you feel regarding those changes. That looks more like a (non-critical) bugfix to me, than a real new feature, so imho if you are confident about it, it could as well go into 2.80.

Sergey Sharybin (sergey) added inline comments.Jul 5 2019, 4:00 PM

source/blender/alembic/intern/abc_mesh.cc
1318	This seems a bit weird to me. Can you elaborate a bit?

Sybren A. Stüvel (sybren) added inline comments.Jul 5 2019, 4:37 PM

source/blender/alembic/intern/abc_mesh.cc
1318	Alembic's 'SubD' scheme is used to store subdivision surfaces, i.e. the pre-subdivision mesh. Currently we don't even add a subdivison modifier when we load such data. This code is assuming (so it should have a comment stating this) that the subdivided surface should be smooth, and sets a flag that will eventually mark all polygons as such. Before this commit the mesh data was just loaded as-is and presented flat shaded.

Added comment about smoothing in SubD loading
Alembic export: fix exporting of loop normals

Harbormaster completed remote builds in B4009: Diff 16289.Jul 10 2019, 10:43 AM

I've fixed exporting loop normals as well; now things load properly in Gaffer as well as Blender, so I'm confident this is a proper bug fix (or two).

If you accept before 15:00 I'll push this to master for inclusion in 2.80 RC :)

Sybren A. Stüvel (sybren) marked an inline comment as done.Jul 10 2019, 10:48 AM

Don't add this to 2.80, no risky changes like this right before the RC.

Sybren A. Stüvel (sybren) mentioned this in T61375: Alembic export does not export smoothing groups.Jul 10 2019, 10:54 AM

Sybren A. Stüvel (sybren) edited the summary of this revision. (Show Details)

Sybren A. Stüvel (sybren) retitled this revision from Alembic import: load face-varying normals to Alembic: import & export face-varying normals.Jul 11 2019, 10:22 AM

Sybren A. Stüvel (sybren) mentioned this in T56792: Alembic doesn't export custom normals correctly.

Sybren A. Stüvel (sybren) mentioned this in T65816: Exporting procedural mesh animation with Alembic results in a static mesh and can cause crashes.Jul 23 2019, 12:30 PM

This revision was not accepted when it landed; it landed in state Needs Review.Jul 30 2019, 5:07 PM

Closed by commit rBe9c149d911c2: Alembic import: load face-varying normals (authored by Sybren A. Stüvel (sybren)). · Explain Why

This revision was automatically updated to reflect the committed changes.

Sybren A. Stüvel (sybren) added a commit: rBe9c149d911c2: Alembic import: load face-varying normals.

Sybren A. Stüvel (sybren) mentioned this in T70710: Alembic cache of Cloth Sim unaffected by Smooth/Flat shading..Oct 13 2019, 12:09 PM