Bone Constraints: IK & Copy Scale #42202

New Issue

Karja Krähwald · 2014-10-13T07:58:39+02:00

Karja Krähwald commented

2014-10-13 07:58:39 +02:00

System Information
Windows 7 64, HD 5770

Blender Version
Broken: 95182d1 (2.72 release) + ee5936c

Short description of error
Not sure if this is a bug.

Armature Pose Mode: Bones with Copy Scale constraint cant display correct scale if their rotation has changed with IK constraint or even Copy Rotation IK.

Exact steps for others to reproduce the error
IK_Scale.blend

Add an Armature, go into Editmode.
- Add 2 Bones: IKbone and TARGETbone
- Set them up for Inverse Kinematics (IK).
- Give IKbone a Copy Scale constraint.
  - Use TARGETbone as target.

Scale and rotation of IKbone is now controlled by TARGETbone.

Move TARGETbone to change IKbones rotation.
Scale TARGETbone to change IKbones scale.

Problem:
The IKbones scale works as if it has no rotation.

Note: This applys also to bones that take rotation from an IKbone via Copy Rotation constraint. (Green bone in picture)
Its like a link to the "buggy" IK rotation, but it appears to be different.

**System Information** Windows 7 64, HD 5770 **Blender Version** Broken: 95182d1 (2.72 release) + ee5936c **Short description of error** Not sure if this is a bug. Armature Pose Mode: Bones with Copy Scale constraint cant display correct scale if their rotation has changed with IK constraint or even Copy Rotation IK. **Exact steps for others to reproduce the error** [IK_Scale.blend](https://archive.blender.org/developer/F116364/IK_Scale.blend) ![IK_Scale.png](https://archive.blender.org/developer/F116365/IK_Scale.png) - Add an Armature, go into Editmode. - Add 2 Bones: IKbone and TARGETbone - Set them up for Inverse Kinematics (IK). - Give IKbone a Copy Scale constraint. - Use TARGETbone as target. Scale and rotation of IKbone is now controlled by TARGETbone. - Move TARGETbone to change IKbones rotation. - Scale TARGETbone to change IKbones scale. **Problem:** The IKbones scale works as if it has no rotation. Note: This applys also to bones that take rotation from an IKbone via Copy Rotation constraint. (Green bone in picture) Its like a link to the "buggy" IK rotation, but it appears to be different.

Karja Krähwald commented

2014-10-13 07:58:39 +02:00

Changed status to: 'Open'

Karja Krähwald commented

2014-10-13 07:58:39 +02:00

Added subscriber: @karja

Bastien Montagne commented

2014-10-13 08:00:13 +02:00

Added subscriber: @mont29

Bastien Montagne commented

2014-10-13 08:00:13 +02:00

Please always attach a .blend file to help us reproducing the issue.

Karja Krähwald commented

2014-10-13 08:15:12 +02:00

Was attached. (above picture :D)

Bastien Montagne commented

2014-10-13 08:20:14 +02:00

Meh, sorry, my bad :/

Bastien Montagne commented

2014-10-13 08:35:43 +02:00

Added subscriber: @JoshuaLeung

Bastien Montagne commented

2014-10-13 08:35:43 +02:00

Ok, so this is really complex to fully understand what happens here… But imho, you are suffering a well known limitation of current constraints system - space evaluation of constraints is done from 'org' situation of the bone/object, not from previous constraint's result. This is a major limitation that tend to often breaks advanced setup compared to expected results…

Joshua, would say we can close it as known TODO?

Ok, so this is really complex to fully understand what happens here… But imho, you are suffering a well known limitation of current constraints system - space evaluation of constraints is done from 'org' situation of the bone/object, **not** from previous constraint's result. This is a major limitation that tend to often breaks advanced setup compared to expected results… Joshua, would say we can close it as known TODO?

Joshua Leung commented

2014-10-13 15:13:27 +02:00

Changed status from 'Open' to: 'Archived'

Joshua Leung closed this issue

2014-10-13 15:13:27 +02:00

Joshua Leung self-assigned this 2014-10-13 15:13:27 +02:00

Joshua Leung commented

2014-10-13 15:13:27 +02:00

The main thing you're actually seeing here is the fact that IK chains only get solved after all the other constraints in the bone have been handled. So, regardless of where you place those constraints, they'll still get evaluated first, and then the IK solver goes over the top and tries to calculate what the transforms should be.based on what it has seen.

So, I think this is probably a known todo.

The main thing you're actually seeing here is the fact that IK chains only get solved after all the other constraints in the bone have been handled. So, regardless of where you place those constraints, they'll still get evaluated first, and then the IK solver goes over the top and tries to calculate what the transforms should be.based on what it has seen. So, I think this is probably a known todo.

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Bone Constraints: IK & Copy Scale #42202