Blender Git Loki

Sculpt: Cloth Simulation Dynamic area mode

This simulation area mode moves the active area with the brush. When
enabled, the cloth brush has no restrictions on stroke length, area or
mesh vertex count.

In order to work, this enables PBVH nodes dynamically for simulation as
the stroke location moves and builds the constraints for new nodes
during the stroke. When a node is not inside the simulated area, all the
constraints that were created for it and vertex collisions are not
computed. The simulation limits falloff areas and constraints tweaking
control how the simulated and no simulated nodes blend.

Reviewed By: sergey, zeddb

Differential Revision: https://developer.blender.org/D8726