The Biped filter generates rotation information based on an initial configuration of the model to which the data is applied. The reasons for building the model in the following recommended configuration are:
Therefore, we recommend that you construct the model with its back on the XY plane, facing down the Z axis. Build the arms and legs with the right limbs pointing down the -X axis and the left limbs pointing down the +X axis. Position the hands with the thumb (if extended) pointing down the +Z axis. Position the feet with the toes pointing down the +Z axis.
If you have constructed the model correctly, with Y-up set in your preferences, the model faces you in the Front modeling window as shown below.
If the model was constructed in a Z-up configuration, the above view shows in the Top modeling window.
