A Direct Method for Positioning the Arms of a Human Model

Many problems in computer graphics concern the precise positioning of a human figure, and in particular, the positioning of the joints in the upper body as a virtual character performs some action. We explore a new technique for precisely positioning the joints in the arms of a human figure to achieve a desired posture. We focus on an analytic solution for the IK chains of the model's arms and an interface for conveniently specifying a desired targeting point, or articulator, on the model's hand. Also, we consider the problem of specifying a target for that articulator in space or in contact with the model's own body. These methods recast the seven degrees of freedom in the arm to provide a more intuitive interface for animation. We demonstrate the efficacy and efficiency of these techniques in positioning a virtual American Sign Language interpreter.