Bones acting as pseudo roots even when the option is not enabled
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Symptom
While working with IK chains you notice that some of the joints of the IK chain behave like Pseudo roots. On investigating the property page for the joint, Kinematic joint > General > Joint Behaviour, the Joint is Pseudo-Root option is not turned on. There seems to to be no explanation for the joint behaving like a Pseudo root
Cause
This is partly due to Bug # 80773 XSI-Bone acting as Pseudo root when upvector constraint added to second(or consecutive) bone/s in the chain.
The fact is that there is no reason to add an upvector to any bone other than the first bone of your IK chain. Since the function of the upvector constraint is to control the resolution plane of the IK chain, placing this constraint on the first bone is the correct workflow to adopt.
Solution
Note that deleting the upvector operator from the joint property stack will not solve the problem.
You can go into Kinematic joint > General > Joint Behaviour, and toggle the Joint is Pseudo-Root option on and off. This will solve the problem. However, it is a better idea to create a new IK chain and place the upvector constraint only on the first joint of the chain.
Applies To: XSI 2.0.1 on NT,Win2K
Posted: 6/20/2002
