Blender Git Loki

Scale damping by spring length as well

I had forgotten to scale the damping forces...
This made for uneven damping on irregular meshes.

Fix previous error with spring length scaling

Zero-length springs weren't being scaled properly, leading to phantom
forces that introduced rigid-body motion into the simulation.

Implement improved compression model

This implements the Choi and Ko compression model, with an added damping
component, instead of using the same model as for tension, which
improves stability of the internal forces.

Code clean-up (remove unnecessary struct members and add comments)

Spring forces and jacobians (f, dfdx and dfdv), were unnecessarily being
stored in sring struct. They are only used locally at computation time,
and don't have to remain in memory.

editrestlen was unused.

Implement separate tension and compression components

Separate shear damping from structural damping

Make structural springs act in both extension and compression

Fix spring force scaling based on length

Separate cloth shear from structural stiffness