In an attempt to address the artistic control issues, the Animator program tries to provide a direct manipulation motion sculpting interface. The animator program allows the user to interactively position the limbs of a human figure. The program uses several methods to position the limbs. The first is a forward kinematic dialing of rotation about a link's coordinate axes. Another is the translation of the entire figure in world coordinate space. The final movement method is the dragging of a limb's end effector. The animator program then provides the rotations of the chain's higher links. This is the first step toward a higher level of user control that retains the direct manipulation interface.
The animator program attempts to allow the direct manipulation of the figure by pointing with the mouse and clicking on multidimensional handles attached to the figure. The handles were modeled after Bier's "skitters" [21].
To rotate a single link, the user specifies either a single link chain or holds down the control key for control of a lower level link. By selecting the x,y or z axis of a small coordinate frame centered at the link's origin, the user may specify which axis to rotate around. The mouse x or y motion (whichever is greater) is then used as a dial to increase or decrease the rotation about the selected axis.
The same axis selection method is used to drag the root link of the figure in one of the principal axes of world coordinate space.
If the user does not desire a single link rotation, a kinematic chain is created upon selection of a link. This chain extends from the selected end effector link up the figure hierarchy to a link with more than one child or the root link, whichever comes first. Once the chain is created, the end effector's coordinate axis handle is displayed. By picking one of these axes, the user can drag the end effector through space as the software calculates the intermediate joint angles of each link in the chain.
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