Achieving Consistency in a Combined IK/FK Interface for a Seven Degree-of-Freedom Kinematic Chain

Abstract

Many applications in computer animation portray the motion of a human arm and torso. Often such applications can benefit from a combination of Inverse (IK) and Forward (FK) Kinematics controls to manipulate the arms of the model. The human arm is a kinematic chain with seven degrees of freedom. The previous analytic solution to this kinematic chain gives highly detailed IK controls, but problems arise when integrating it with FK controls. These problems impede the artistic process when creating expressive animations. This work improves on the previous analytic solution to create a hybrid FK/IK control interface for manipulating the chain, and enables the recalculation of all the parameters necessary for the IK solution. Thus IK and FK controls can interact seamlessly to manipulate the arm. The torso is modeled as a separate kinematic chain, and is integrated with the arm linkages. User tests demonstrate the effectiveness and efficiency of the combined FK/IK control interface.