Determines whether this instance is valid or not. If returns false, also fills in an error message. Implemented in IKSolverFullBodyBiped, IKSolverVR, IKSolverLookAt, IKSolverTrigonometric, IKSolverFullBody, IKSolverHeuristic, IKSolverArm, IKSolverLeg, and IKSolverFABRIKRoot. |