Blender Git Loki

Automatically re-evaluate the flow solution on hair updates, as a
replacement for the current distribution system.

Use a particle system flag to toggle hair flow calculation.

Moved the hair flow solve operator out of the hair edit mode.

The reason is that the flow calculation will be based on external
objects and also conflict with the edit mode tools. Flow-based grooming
calculates the hair rest state just like edit mode does, but is an
alternative to the edit mode instead of a single tool.

Revert "New `mode` enum for hair edit mode to toggle between direct mesh-style"

This reverts commit b29a6f1c5b4badd4dfe8c50b6925e7e18fdf350f.

Use the interpolation direction of the hair flow for integrating
hair strands.

Gradient calculation and normalization from the pressure field.

Solver for the pressure Poisson equation on hair flow grids.

Note: does not include boundary conditions so far.

First step toward hair directional flow solving: Calculate divergence
from "source" (emitter) meshes.

New grid struct for hair volumetrics.

This is supposed to unify volumetric calculations for hair edit mode
and dynamics eventually.

Simple hair strand integration function for the flow operator.

Stub handling of hair edit mode switch for the undo system.

Undo is not implemented for hair edit mode yet, but this prevents
operators from reloading blend files on redo, which otherwise exits
hair edit mode without cleaning up.

Simple operator for solving and integrating the hair flow grid.

This would probably become an automatic update running in a job
eventually, but for testing this is the easiest implementation.

New strand functions in the physics library for solving hair flow grids.

New `mode` enum for hair edit mode to toggle between direct mesh-style
editing and flow solver editing.

The flow mode could be used to disable mesh vertex drawing and operators
and instead enable automatic recalculation of the hair flow field and
sampling strands.

Select Linked operator for hair edit mode (select all vertices of a
strand).

Lasso Select operator for hair edit mode.

Border Select operator for hair edit mode.

Mouse Select operator for hair edit mode.

Select/Deselect All operator for hair edit mode.

Disabled the partial IK strand relaxation for the time being.

First goal is to reproduce current particle edit tools in the strand
edit mode, then make improvements.