On Carrara 3, I am trying to animate a model with IK. There seems to be two ways to set constrains. One, directly on the "Motion" tab selecting a pre-determend bone/joint, the second is under the Skinning menu. They seem to work independently from one to the other. What is the deference between them, and which should I use? Is it the same thing? I also heard that this process has been upgraded on Carrara 4. Any comments on this? I appreciate your help.