There are two main reasons for defining a biped's pose in Figure mode:
Fitting the biped to a mesh in preparation for using Physique to attach the mesh to the biped. Leave Figure mode on during the attach procedure in Physique.
To correct posture in a motion file.
A particular motion file may position a biped body part inappropriately; for example, the collar bones may be rotated down too far, affecting your mesh deformation. Simply rotating the biped collar bones up and exiting Figure mode corrects the collar bone position for the entire animation. The motion references the Figure mode position, if the biped is adjusted, and this adjustment is reflected in your animation when you exit Figure mode.
Note: Save a .FIG file for the biped pose you used when you applied Physique. You could use the .FIG file to reload this position, if you need to reapply the Physique modifier or reinitialize the Physique settings.
When you animate the biped, the Biped plug-in maintains the at-rest pose you have created for these elements of the biped body:
Center of mass position, relative to the body.
When Biped adapts the keyframed motions stored in .BIP files to different characters, the keyframes of the above elements are recreated as an offset from the at-rest posture associated with each character's figure. The at-rest posture associated with the arms and legs is always assumed to be a standing posture, with straight legs.
When you load a .BIP file, there is an option to restructure the biped to match the file. If you turn this on, when you load the file, the biped's structure will change to match the figure of the biped in the .BIP file.
Talent Figure Mode and Adjust Talent Pose on the Motion Capture rollout are used in functions similar to that of Figure mode. They are used to size and position biped body parts to better fit raw motion capture data. After importing motion capture data, you may discover that certain biped limbs or the biped scale need a global adjustment in order to provide a closer match to the figure of the talent who performed the motion.
Motion Capture rollout