Hey y'all. Couple of questions. First when I try setting up a character with up vector constraints for my arm chain, the chain always flip-flops the elbows into the opposite direction. I am placing them behind and above where the elbow joint would be. How can I get the up vect constraints to work properly in the chain? Second, when I try using an offset map in the mixer it only works sometimes. I know there's something I'm over looking but I can't see it yet, how can I fix this? Thanks!
Offset map works for kinematic parameters such as position, orientation, scaling, etc..., but to place offsets on constraint attributes, you need to use the "offset key" tool available from the animation mixer. Essentially, it saves a keyframe for the current constraint parameters of your clip in a similar fashion to offset maps. If you want a constant value across the clip, then make sure to set the offset key on the first frame of the clip or else XSI will introduce a second offset keyframe at the end of the clip at it's original values.
by "offset key" are you referring to the "action key" because the only two buttons I see are the "offset map" and "action key". Either way I tried both, following the instructions in the manual and from the Maraffi book and everytime I go the frame of the clip and adjust the objects params and press either button it jumps back to the way it was before. Basically I'm animating a simple walk style like the basic skel example in the Maraffi book and I just want to tweek the different walk clips a little, ei:add some rotation in the ankles, more arm sway, etc. I'm totally stumpified.
In regards to the up vector. This will be the up vector in an arm chain of two bones. When I draw a 2d chain in top view(to put bend in the elbows for the IK) then add a null, position it behind the elbow region and then upvector the 1st bone in the chain to the null it flip flops the elbow into the opposite direction. When I try to offset it in the bones param menu nothing happens. What's wierd is when I draw the chain backwards(with the elbows pointing forwards) then do the same steps it flip flops the right way. I would say great, but I think doing it this way may lead to IK and animation problems later. Any advice?
I had the same problem when constraining the right arm of a characterI was creating. However I was told by one of the tutors that moving the up vector null to the other side of the arm i.e. in front of the body, the arm would flip back into it's correct position, and you should experience no problems when it comes to animating (the null is only a point in space that creates a plane for the arm to rotate in). I rigged my character with this setup, and I had no problems. It might also be worth making the upvectors children to their respective arm roots so they follow the body correctly.