View Full Version : XSI Biped IK Problem

02 February 2007, 08:04 AM
Hey everyone,

Ok I am a bit of a newbie to XSI and I am now getting accustom to the setup and the interface. Coming from a Maya background things are still a little tricky. I have one question concerning the XSI Biped rig for 6.0.

I created the biped and everything works fine, but I am unable to figure out why the IK controls do not work like Maya's IK controls. If I switch the arm bones to IK and then I decided to move the main control for the up and down movements of the rig the IK arms do not stay to its location. It begins to move with the whole body like it was in an FK setup. I am not sure how to go around solving this issue so I may be able to get good weight for my animation. So basically to make things short my question is how do I fix this issue or is it something simple in the setup that need to be switched on?

I have pasted some shots from Maya to explain my question clearer.

02 February 2007, 11:17 AM
XSI Ik behaves a bit diferent, since the IK Eff is child of the last Bone, you can Cut it from the Hierarchy but wont do any good.

What you need is to Pose Constraint the Eff to another Object and use that as the mover of the IK, and there yah go... IK like in Maya :)

simple steps:

- Make an Implicit or a new Null

- Match Translation of the new Null to the Eff

- Pose Constraint the Eff to the new Null

02 February 2007, 07:27 PM
XSI Ik behaves a bit diferent, since the IK Eff is child of the last Bone, you can Cut it from the Hierarchy but wont do any good.

You need to check "force IK" for the IK effector to remain independent of the root when you parent it under something else, so you dont have to constrain it to anything if you don't want to.

A good method for IK controllers is to parent the ik effector under a transform group (or a null), and then pose constraint that transform group/null to multiple parts of the body (like the shoulder, upper torso, hips, GlobalSRT), and then blend inbetween the constraints. This lets you switch between what is the "parent" of the IK effector while animating.

02 February 2007, 06:45 AM
Good stuff guys. I definatley see what you are saying. I am going to try it out and see how it works. Thanks a bunch.


02 February 2007, 09:30 PM
avoid pose constraing the effector directly it will break ik/fk blending.
Instead, follow Tuna suggestion and constrain a null which the parent of the effector.

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02 February 2007, 09:30 PM
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