Basic Theory
There are several components to such a simulation system:
- a polygon mesh defining the body shape of the model
- a coarse volumetric mesh using finite element methods to ensure complete integration over the model
- line constraints corresponding to internal skeleton and instrumented to the model
- linearizing of equations of motion to achieve interactive rates
- hierarchical regions of the mesh associated with skeletal lines
- blending of locally linearlized simulations
- a control lattice through subdivision fitting the model by surrounding and covering it
- a hierarchical basis containing functions which will provide values for deformation of each lattice
domain with calculations of these hierarchical functions similar to that of lazy wavelets
Rather than fitting the object to the skeleton, as is common, the skeleton is used to set constraints for deformation. Also the hierarchical basis means that detail levels can be introduced or removed when needed - for example, observing from a distance or hidden surfaces.
Pre-calculated poses are used to be able to interpolate between shapes and achieve realistic deformations throughout motions. This means traditional keyframes are avoided.
There are performance tuning similarities between this technique and procedural generation, wavelet and data compression methods.
Read more about this topic: Interactive Skeleton-driven Simulation
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