Automatic Weighting of Armature Fails Unless Normals Recalculated #37685

New Issue

Kyle Horseman · 2013-12-03T01:06:38+01:00

Kyle Horseman commented

2013-12-03 01:06:38 +01:00

System Information
Mac OS X 10.9 (13A603), iMac, ATI Radeon HD 4670
Also encountered on what I assume are not identical systems, see Blender Artists link below.

Blender Version
Broken: Blender 2.69 r60991 confirmed. First noticed problem in 2.67 but was unable to find confirmation from other users until now.

Problem: Parenting an armature with automatic weights intermittently generates only empty vertex groups. Recalculating normals on the whole mesh immediately before parenting consistently fixes the problem, even in cases where normals were already correct and recalculating normals seems to have no real effect (other than allowing parenting to work properly, of course).

Exact steps for others to reproduce the error
GameCharacter3.blend
Without doing anything else first, select the character mesh, then a bone and parent with automatic weights. Pose the armature; the mesh does not follow. Vertex groups are created appropriately, but no vertices are assigned to any of them at any weight.

On the same file, recalculate normals on the entire mesh, then parent with automatic weights again. Weights are assigned as regularly expected. It is not clear to me what causes the problem, but this solution seems to work in all cases. The problem does not happen with every mesh, so I have been unable to get good confirmation until others noticed the issue with far simpler rigs and meshes, such as the attached. See also: http://blenderartists.org/forum/showthread.php?319559-%28Solved%29-Parenting-Mesh-to-Armature-Adds-Vertex-Groups-But-No-Weights&p=2527269#post2527269

**System Information** Mac OS X 10.9 (13A603), iMac, ATI Radeon HD 4670 Also encountered on what I assume are not identical systems, see Blender Artists link below. **Blender Version** Broken: Blender 2.69 r60991 confirmed. First noticed problem in 2.67 but was unable to find confirmation from other users until now. Problem: Parenting an armature with automatic weights intermittently generates only empty vertex groups. Recalculating normals on the whole mesh immediately before parenting consistently fixes the problem, even in cases where normals were already correct and recalculating normals seems to have no real effect (other than allowing parenting to work properly, of course). **Exact steps for others to reproduce the error** [GameCharacter3.blend](https://archive.blender.org/developer/F36129/GameCharacter3.blend) Without doing anything else first, select the character mesh, then a bone and parent with automatic weights. Pose the armature; the mesh does not follow. Vertex groups are created appropriately, but no vertices are assigned to any of them at any weight. On the same file, recalculate normals on the entire mesh, then parent with automatic weights again. Weights are assigned as regularly expected. It is not clear to me what causes the problem, but this solution seems to work in all cases. The problem does not happen with every mesh, so I have been unable to get good confirmation until others noticed the issue with far simpler rigs and meshes, such as the attached. See also: http://blenderartists.org/forum/showthread.php?319559-%28Solved%29-Parenting-Mesh-to-Armature-Adds-Vertex-Groups-But-No-Weights&p=2527269#post2527269

Kyle Horseman commented

2013-12-03 01:06:38 +01:00

Changed status to: 'Open'

Kyle Horseman commented

2013-12-03 01:06:38 +01:00

Added subscriber: @KHorseman

Brecht Van Lommel self-assigned this 2013-12-06 14:31:03 +01:00

Kyle Horseman commented

2013-12-07 18:41:00 +01:00

It's also been noted that you can't assign auto weights to a mesh that has no faces. I think this might be intended behavior, but it seems there might be an error checking step during the auto weights process related to this. I've done a few tests on the GameCharacter3.blend file. It seems that the recalculate normals workaround still works even if you first delete a large number of faces (leaving the connecting edges intact), but if there are zero faces, it will not work. If you delete a significant region of faces (for instance the whole torso, but leaving the head, arms and legs intact), auto weights will work for the regions with faces if you recalculate normals again, but no weights will be assigned where there are no faces.

Again, not sure if this is related, and the "no faces, no auto weights" behavior seems like it might be intended (though I'm not sure why), but if there is some kind of related error checking it seems like it could contribute to the original problem. There's a related BA thread here: http://blenderartists.org/forum/showthread.php?320083-rigging-wire-%28no-face%29-mesh&p=2530610#post2530610

It's also been noted that you can't assign auto weights to a mesh that has no faces. I think this might be intended behavior, but it seems there might be an error checking step during the auto weights process related to this. I've done a few tests on the GameCharacter3.blend file. It seems that the recalculate normals workaround still works even if you first delete a large number of faces (leaving the connecting edges intact), but if there are zero faces, it will not work. If you delete a significant region of faces (for instance the whole torso, but leaving the head, arms and legs intact), auto weights will work for the regions with faces if you recalculate normals again, but no weights will be assigned where there are no faces. Again, not sure if this is related, and the "no faces, no auto weights" behavior seems like it might be intended (though I'm not sure why), but if there is some kind of related error checking it seems like it could contribute to the original problem. There's a related BA thread here: http://blenderartists.org/forum/showthread.php?320083-rigging-wire-%28no-face%29-mesh&p=2530610#post2530610

blender-admin commented

2014-01-23 17:47:20 +01:00

This issue was referenced by blender/blender-addons-contrib@0847549009

This issue was referenced by blender/blender-addons-contrib@08475490097cf7445423ddc57b8de9eac5f5470c

blender-admin commented

2014-01-23 17:47:20 +01:00

This issue was referenced by 0847549009

This issue was referenced by 08475490097cf7445423ddc57b8de9eac5f5470c

Brecht Van Lommel commented

2014-01-23 17:49:27 +01:00

Changed status from 'Open' to: 'Resolved'

Brecht Van Lommel closed this issue

2014-01-23 17:49:27 +01:00

Brecht Van Lommel commented

2014-01-23 17:49:27 +01:00

Closed by commit 0847549009.

Closed by commit 0847549009.

Brecht Van Lommel commented

2014-01-23 17:51:09 +01:00

Turns out this isn't related to the normals. The problem is that in weight paint mode face masking is enabled and no faces are selected, and this was influencing object mode too. It should just compute weights for the entire object in that case.

Recalculating the normals happens to require you to select all faces, so afterwards the weight calculation worked. Fixed now, thanks for the report.

Turns out this isn't related to the normals. The problem is that in weight paint mode face masking is enabled and no faces are selected, and this was influencing object mode too. It should just compute weights for the entire object in that case. Recalculating the normals happens to require you to select all faces, so afterwards the weight calculation worked. Fixed now, thanks for the report.

Kyle Horseman commented

2014-01-24 15:20:15 +01:00

Heh. You can always count on me to suggest a complete red herring solution. Thanks brecht!

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Automatic Weighting of Armature Fails Unless Normals Recalculated #37685