Dual quaternion skinning behaves strangely with scaling #32022

New Issue

Nathan Vegdahl · 2012-07-05T23:39:52+02:00

Nathan Vegdahl commented

2012-07-05 23:39:52 +02:00

%%%When a mesh has an armature modifier on it, and the bones of the modifier are both rotated and scaled, strange deformations occur that are not expected.

See in the attached blend file. When you play back the animation, the bones first rotate to bend the mesh, and then they uniformally scale to a smaller size. One would expect the mesh to also uniformally scale to a smaller size, but instead the mesh expands (relative to the size of the bones) in a strange way. Similarly--though more subtly--when the bones are scaled non-uniformally, one would expect the mesh to also scale in the same way as the bones, but similar strange deformations occur as in the uniform case.

This is very problematic for rigs that need to allow the scaling of bones (e.g. for flexy rigs, squash-and-stretch, etc.)

I'm not sure if this is an inherent limitation of dual quaternion skinning. If it is, then oh well. But if it is not, then it needs to be fixed.%%%

%%%When a mesh has an armature modifier on it, and the bones of the modifier are both rotated and scaled, strange deformations occur that are not expected. See in the attached blend file. When you play back the animation, the bones first rotate to bend the mesh, and then they uniformally scale to a smaller size. One would expect the mesh to also uniformally scale to a smaller size, but instead the mesh expands (relative to the size of the bones) in a strange way. Similarly--though more subtly--when the bones are scaled non-uniformally, one would expect the mesh to also scale in the same way as the bones, but similar strange deformations occur as in the uniform case. This is very problematic for rigs that need to allow the scaling of bones (e.g. for flexy rigs, squash-and-stretch, etc.) I'm not sure if this is an inherent limitation of dual quaternion skinning. If it is, then oh well. But if it is not, then it needs to be fixed.%%%

Nathan Vegdahl commented

2012-07-05 23:39:52 +02:00

Changed status to: 'Open'

blender-admin commented

2012-07-05 23:39:52 +02:00

#43188 was marked as duplicate of this issue

Ton Roosendaal commented

2012-10-20 13:15:53 +02:00

%%%Bump up to brecht to check on this :)%%%

Julian Eisel commented

2014-12-23 04:50:30 +01:00

Added subscriber: @JulianEisel

Julian Eisel commented

2014-12-23 04:50:30 +01:00

This is an old report an unlikely to be tackled anytime soon
I read a bit about dual quaternion skinning and if I understand correctly this is a known limitation of the original algorithm. It was improved in the meanwhile, but that would be a feature request, not a bug

So I think after 2 years it's time to close this \o/

1. This is an old report an unlikely to be tackled anytime soon 2. I read a bit about dual quaternion skinning and if I understand correctly this is a known limitation of the original algorithm. It was improved in the meanwhile, but that would be a feature request, not a bug So I think after 2 years it's time to close this \o/

Julian Eisel commented

2014-12-23 04:50:46 +01:00

Changed status from 'Open' to: 'Archived'

Julian Eisel closed this issue

2014-12-23 04:50:46 +01:00

Julian Eisel commented

2015-02-23 23:39:47 +01:00

Added subscribers: @LucasVeber, @JoshuaLeung, @LukasTonne, @mont29

himisa commented

2023-05-21 20:15:13 +02:00

Still present in latest blender. This should be fixed!

32022.blend

1.1 MiB

himisa commented

2023-05-21 20:37:10 +02:00

I guess to fix this, we should modify the function

static void armature_vert_task_with_dvert(const ArmatureUserdata *data,
                                          const int i,
                                          const MDeformVert *dvert);

in blender\source\blender\blenkernel\intern\armature_deform.c ?

I guess to fix this, we should modify the function ```C static void armature_vert_task_with_dvert(const ArmatureUserdata *data, const int i, const MDeformVert *dvert); ``` in blender\source\blender\blenkernel\intern\armature_deform.c ?

himisa referenced a pull request that will close this issue

2023-05-22 08:42:58 +02:00

Fix #32022, #43188, #100373, Armature modifier - Preserve volume + Scale #108134

Nathan Vegdahl referenced this issue from a commit

2023-06-06 12:32:01 +02:00

Fix #32022, #43188, #100373, Armature modifier - Preserve volume + Scale

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