1. A computer-implemented method for providing retargeting of actor motion to a virtual character, the method comprising: enabling a user to select one or more real-time constraint scenarios from a plurality of real-time constraint scenarios, each real-time constraint scenario corresponding to a relationship between motion capture information from an actor and a position or movement of a character having a plurality of limbs driven by the motion capture information; receiving, in a computer system, input generated by user selection of the one or more real-time constraint scenarios; activating, based on the one or more selected real-time constraint scenarios, a first limb solver associated with a first limb in the plurality of limbs to calculate at least a first joint angle for the first limb, wherein the first limb solver is configured to calculate movement of the first limb from the motion capture information; based on the one or more selected real-time constraint scenarios, obtaining a corresponding joint angle for a second limb in the plurality of limbs directly from the motion capture information and registering the corresponding joint angle as a second joint angle for a second limb in the plurality of limbs without activating a second limb solver configured to calculate movement of the second limb from the motion capture information; and determining a root location for the character based on at least the first and second joint angles.