After creating the default biped, you may need to change the proportions of the skeleton. You use Figure mode to allow changes to occur to the biped structure. With the biped selected, choosing Figure mode returns the biped to its original creation location and orientation. With the biped in Figure mode, you can use the 3DS MAX transform tools to change the proportions and positions of body parts. For instance, you might apply a non-uniform scale to shorten the legs for a cartoon character.
Biped proportioned to fit inside of Dr. X character geometry
You might rotate the spine objects to create the figure for a hunchback or a dinosaur. Use the move tool to change the position of the thumb or the arms.You can even apply modifiers to the biped skeleton pieces, such as using an FFD on the biped head to adjust its shape.
FFD Modifier used to shape spine and head
Once you have a default biped, you'll need to match its proportions to the character's geometry. It is quite typical to find the character's geometry with the arms outstretched. The common workflow is to freeze the character and then in Figure mode, reposition the biped, so the center of mass is at the base of the torso. The spinal objects, legs, and feet are scaled and rotated to fit within the confines of the mesh, then the arms and hands, neck and head. The tail and ponytail objects can be used for animating wings, fins, jaws, ears, horns, or hair.
Once your biped proportions are correct, you can save them in a .FIG file. Since biped saves the character in the .FIG file, and then animation in the .BIP file, you can change the character's proportions without affecting the animation.
Changing the Initial Biped Structure
Posing a Biped
Saving and Loading Biped Figure Files
Rubber Banding Arms and Legs
Rubber Banding the Center of Mass
Linking Objects to the Biped