Optimize Pose For IK

The MHX and Rigify rigs are advanced rigs which allow for IK (inverse kinematics). However, IK works best when the joints (elbows and knees) are slightly bent in the preferred bending direction. For Daz rigs this is usually not a problem for the elbows, but sometimes the legs are almost perfectly straight and the knees are hardly bent at all. In that case IK may not work as expected. To avoid this problem, press Optimize Pose For IK.

There is an option to apply the optimized pose as rest pose. Alternatively, that can be done explicitly with the Apply Rest Pose button.

This picture shows how optimizing the rest pose affect Aiko. The thighs are rotated forward and the shins back, so the knee is bent in the preferred direction.