Home | Lehre | Videos | Texte | Vorträge | Software | Person | Impressum, Datenschutzerklärung | Blog RSS


Inverse Kinematics

Consider the hierarchical structure of skeletons: The lower arm inherits translation/rotation/scaling from the upper arm, the hand inherits from the lower arm and so on (simply products of matrices!). A basic way of animation is to set the rotation for the upper arm, then for the lower arm, then for the hand ("Forward Kinematics", FK). It is hard to reach a given target such as a coffee cup using FK. "Inverse Kinematics", IK, is a standard way to solve this problem. Here the software simulates how a chain of limbs would behave if one drags the final element. Typically, one can set limits for angles.


In order to animate a face, one typically stores several versions ("morph targets", "blend shapes") of its geometry and blends them in different percentages, storing only these percentage values as animation. Typical morph targets are "visemes" (mouth shapes for particular sounds; compare "phonemes") plus facial expressions such as similing, frowning, etc. Advantages: much less memory comsumption than recording all vertices; much easier to handle. Typcially, all morph targets have to have the same mesh structure, differing only in the positions of the vertices. To blend several shapes, form a weighted average vertex by vertex. The weights control the balance of the shapes. Negative weights and weights in excess of 100 % are interesting, though most 3D software doesn't offer them.