Blender Git Loki

Reimplemented the voxel texture type for displaying hair continuum grids.

Expose hair grid info in the RNA (read-only); it can be useful for
debugging purposes.

Debug visualization code of a slice of the hair velocity vector field.

Removed arbitrary factor 2.0 on volumetric hair friction factor.

This was introducing energy into the system for any factor beyond 0.5
and caused major instability.

Fill the hair volume grid with the _new_ velocities from the first
solver step, instead of using the previous step's velocities.

Merge branch 'master' into viewport_experiments

Debug drawing feature to visualize the hair continuum grid.

Perform grid-based velocity smoothing for hair outside of the implicit
solver step.

Calculating forces and jacobians from linearly interpolated grid values
is problematic due to discontinuities at the grid boundaries. The new
approach of modifying velocities after the backward euler solver step
was suggested in a newer paper

"Detail Preserving Continuum Simulation of Straight Hair"
(McAdams, Selle 2009)

Merge branch 'master' into gooseberry

Experimental color wire-frame (for testing in the studio)

Fix for warnings/errors

Merge branch 'master' into hair_immediate_fixes

Reorganizing hair dynamics UI layout a bit to make settings slightly
more intuitive.

Also removed a couple of unused or useless features from the UI:
* collider friction is unused and replaced in favor of true collision
* spring damping refers to structural springs (stretch), which is
not noticable in hair due to extreme stiffness atm.
* pressure factors are not sure since this feature is too unstable atm.

Disabled the hair preview feature in the code, due to limited usefulness.

Interpolating hairs in a meaningful way is a quite difficult problem.
It works ok-ish for child hairs as long as they don't move, but with
motion the direction of interpolated hairs can become quite nonsensical
quickly.

Probably a better way to create simulation previews is to limit
simulation to a particular well-defined area (like render preview
borders), but run it in full detail in that area. The error from
omitting some interaction should still be much less than orientation
errors from interpolation.

Moved render simplification function for particle distribution into the
distribution code.

Removed unused variable.

A little bit of code sanity by splitting particle distribution function
by type.

Instead of squashing totally unrelated code into the same monster
function.

Moved particle code for distributions into own file to make hacking
easier.

This code is badly broken and needs to be replaced, but at least having
a workable code structure might help with quick hacks to fix the worst
cases.

Removed unused line.

Switched back to blender implicit solver for merge.