Blender Foundation: Blender 2.x BF release: Detail: 25341 ChildOf constraint: strange behavior in object mode.

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[#25341] ChildOf constraint: strange behavior in object mode.

Date:
2010-12-22 12:36 Priority:
3

State:
Closed

Submitted by:
Thomas Larsson (thomasl) Assigned to:
Ton Roosendaal (ton)

Category:
Animation system Status:
Fixed / Closed

Relates to: Duplicates:

Patches:

Summary:
ChildOf constraint: strange behavior in object mode.

Detailed description

Windows XP 32 bit
Blender r33799. Behavior changed about a week ago.

In my armature, various bones without parents have a ChildOf constraints targeting the MasterFloor bone below the character. The settings for the Root bone is seen to the right in the picture. When the character is moved in object mode, both the master and its children move, but by different amounts. Also the Hand and Leg IK bones are not in place where they used to be.

I am somewhat confused about the correct semantics of the Set Inverse and Clear Inverse buttons. However, no matter how I (mis-)configure the constraint, the character should move as a single unit in object mode.

Followup

Message

Date: 2010-12-22 16:35
Sender: Ton Roosendaal
It would really be much more helpful if you create the simplest case showing the error. That's half the bugfixing work, which users can help us with.

Date: 2010-12-22 21:28
Sender: Ivo Grigull
I see the double transformation problem after loading the file. Set inverse and clear inverse don't fix it. When i recreate the constraint however everything is fine. I suspect the problem is not in the constraint but the set inverse function somehow producing a wrong matrix. I am now stuck however. Can't really reproduce the problem.

Date: 2010-12-22 21:54
Sender: Rob Waite
OSX 10.6.5
Official Blender release 2.55 and recent build 33838 give the same results...

The rig can be reduced to two bones to demonstrate - root and masterfloor. I'll attempt to attach a simplified file, simple.blend. As Ivo noted above, deleting and recreating the constraint makes things work (in my simple case at least).

R.

Date: 2010-12-23 13:02
Sender: Thomas Larsson
The rig was created with a script; the mhx importer for MakeHuman. I have tried to reproduce it with a simpler script, but not succeeded. The script sets owner space and target space, which I noticed is not accessible from the viewport. However, the behaviour is apparently not affected by the choice of spaces.

For the time being I have replaced all ChildOf constraints with proper parenting. The theoretical drawback is that one cannot change parents during an animation, but in practise I never managed to make this work smoothly anyway.

Date: 2010-12-23 14:16
Sender: Ton Roosendaal
Thanks for the example. I found a bug in the constraint-adding code, which forgot to set a flag in child-of constraints that were needed for bones.
I've patched Blender to set this by default on loading now, so it will work on your saved files as well.

Attached Files:

Name	Date	Download

childof.blend	2010-12-22 12:36	Download
childof1.JPG	2010-12-22 12:36	Download
simple.blend	2010-12-22 21:54	Download

Changes:

Field	Old Value	Date	By

status_id	Open	2010-12-23 14:16	ton
close_date	None	2010-12-23 14:16	ton
assigned_to	none	2010-12-23 14:16	ton
Category	None	2010-12-23 14:16	ton
Status	New	2010-12-23 14:16	ton
File Added	14224: simple.blend	2010-12-22 21:54	vectorspace
File Added	14210: childof1.JPG	2010-12-22 12:36	thomasl
File Added	14211: childof.blend	2010-12-22 12:36	thomasl