Controlling Stance With The Leg & Foot Control Rigs
The base of the full body expression is the Leg Pose Setup Panel. Each leg is controlled from a foot rig. The Mecanim Foot IK uses the ankle pivot to align to the foot IK goal. To get proper pivot to the leg for natural motion the foot should pivot around the heel. Ergo the FootRig root should be placed at surface level to the rear of the heel and the Foot IK Goal the Mecanim AnimatorIK is trying to reach is set at the ankle pivot relative to the heel position. In this setup the FootRig controls positioning and rotation of the foot with the leg and the FootIKGoal. The KneeHint is set up as a child of the FootRig so that any rotations applied to the foot affects the way the bone chain of hip to ankle is rotated at the knee.
The Leg is controlled by a Leg Control Rig object attached to the Thigh bone pivot position and maintain up and forward axes aligned to the pelvis. The Rotator is a child of Leg Rig root with the Extender object a child of the Rotator. The Rotator pivots the Extender from front to back or in and out of the body midline according to the controls settings. The Extender controls the contraction and extension of the Leg and the Foot Rig is attached to its position. Finally, the Foot Rig controls the rotation of the Ankle and Toe bones offset from the Extender rotation.