ExploitingSubdivisioninModelingandAnimation.ppt

Exploiting Subdivision in Modeling and Animation David R. Forsey The University of British ColumbiaRadical Entertainment Inc. Topics Multiresolution Animation What it is. How to use it. Retrospective “Hierarchical B-Spline Refinement”, SIGGRAPH’88  Forsey/Bartels. Motivations for H-Splines H-Splines were developed specifically for animation. Address problems with traditional B-splines non-local knot insertion the “degree-of-freedom” problem. Local Refinement Models rapidly become “heavy” patches in locations they are not needed extra rendering overhead may affect previously defined animation even more points to animate Local refinement adds patches to a restricted area Local Refinement Local Refinement Created using a multiresolution representation Can dramatically reduce the storage requirements Multiresolution Editing Each resolution procedurally related to the next coarsest level arbitrary procedure (offset operator) for each control point. creates a “reactive surface” H-Splines Applicable to any surface formulation with: Local support Subdivision that does not alter the shape of the limit surface polygons other splines (including curves deformation lattices) various subdivision surface formulations wavelets (depending upon basis used) H-Splines Advantages Top-down modelling (more like sculpting) details maintained during broad-scale editing faster/easier to animate complex surfaces Efficient representation (compression) Refinement only where needed Multiresolution Animation Available in a limited form commercially: MetaNURBs (Lightwave) Meshsmooth (3DMax) Symbolics L-surf (now Nicheman) various polygon smoothing packages Animating with H-Splines Offset Operators: tangent plane offset “frame” offset (attaches a control vertex to a skeletal segment) others described later Simple Head Low-Res Attachment Effect on finer resolution Example Animation “Locking down” geometry Locking Down Geometry, Part II Full Detail Lowest Resolution Locking Do