The biped hierarchy that is used to determine the relationships between the biped parent and child body parts is different
than the hierarchy presented by the max nodes parent/child relationships. The main reason for this is to make the biped move
more naturally when being animated. For example, the upper arm links inherit their rotation from the center of mass, instead
of from the clavicle, which they are connected to. This allows the user to animate the spine without having to counter rotate
the arms.
Following is a brief description describing the hierarchy. One thing to note is that the internal biped body parts may have
different parents for both rotation and position.
Rotation Hierarchy
- The base of the spine, the base of the neck, the upper arms and legs, and the feet inherit their rotation from the center
of mass.
- The clavicle inherits its rotation from the last spine link.
- The other biped body parts inherit their rotation from their parent INode.
Position Hierarchy
- The base of the spine inherits its position from the center of mass.
- The clavicle inherits its position from the last spine link.
- The upper leg link inherits their position from the pelvis.
- The other biped body parts inherit their position from the parent INode.
Biped Degrees of Freedom
The following biped body parts lack 3 degrees of freedom.
- The pelvis has 2 degrees of freedom.
- The clavicle has 2 degrees of freedom.
- The knee and elbow have 1 degree of freedom.
- The horse ankle in a 4 link leg have 1 degree of freedom.
- The finger and toe segments, excluding the base, have 1 degree of freedom.
