Blender Git Loki

New hair editing feature "Shape Cut", for cutting hair based on a mesh
shape instead of a brush tool.

The brush cutting tool for hair, while useful, is not very accurate and
often requires rotating the model constantly to get the right trimming
on every side. This makes adjustments to a hair shape a very tedious
process.

On the other hand, making proxy meshes for hair shapes is a common
workflow. The new operator allows using such rough meshes as boundaries
for hair. All hairs that are outside the shape mesh are removed, while
those cutting it at some length are shortened accordingly.

The operator can be accessed in the particle edit mode toolbar via the
"Shape Cut" button. The "Shape Object" must be set first and stays
selected as a tool setting for repeatedly applying the shape.

Switched back to blender implicit solver for merge.

Unified the main Eigen solver function a bit for constrained/unconstrained
solver variants.

Ported the remaining implicit solver functions for Eigen.

Also added a couple of utility wrapper functions for Eigen types to make
interfacing with plain float arrays and blenlib math easier.

Updating Eigen implicit dynamics solver implementation to adhere to the
new mass-spring solver API.

Conflicts:
source/blender/physics/intern/implicit_eigen.cpp

Fix for inverted condition: hair data needs to be rebuilt when the
cloth DM does not exist.

Cleanup: Removed the unnecessary cloth solver abstraction (there is only
one solver anyway), and split some particle cloth functions for clarity.

Conflicts:
source/blender/blenkernel/BKE_particle.h
source/blender/blenkernel/intern/particle_system.c
source/blender/blenloader/intern/versioning_270.c
source/blender/makesdna/DNA_particle_types.h
source/blender/makesrna/intern/rna_particle.c

enum instead of #define for cloth vertex flags.

Removed accidentally committed debug print.

Use the generic task scheduler for threaded particle tasks, i.e.
distribution and path caching for child particles.

This gives a significant improvement of viewport playback performance
with higher child particle counts. Particles previously used their own
threads and had a rather high limit for threading. Also threading
apparently was disabled because only 1 thread was being used ...

Removed block matrix indices storage from ClothSpring struct.

This is not necessary: the implicit solver data can keep track instead
of how many off-diagonal matrix blocks are in use (provided the
allocation limit is calculated correctly). Every time a spring is
created it then simply increments this counter and uses the block index
locally - no need to store this persistently.

Removed unused force arguments for angular bending springs and avoid
redundant calculation for counterforces.

Guide hair drawing for hair particles.

Without this the particle system only shows the actual non-simulated
hairs ("guide hairs") during edit mode. These hairs are used for goals
as well, so showing them in the regular viewport is pretty important.

Also the usual hair curves are interpolated along the entire length,
which makes it very difficult to see exact vertex positions, unless
using exact powers of 2 for the segment number and match the display
steps.

Conflicts:
source/blender/blenkernel/intern/particle.c

Improved child hair curling for interpolated child particles.

The curl radius for children in interpolated mode was calculated using
the total offset from the parent particle. This leads to very large
radii when the distance is large due to sparse parents. Such behavior is
also very unrealistic because the curl radius is mostly constant and
defined by the material properties.

All the child hairs are roughly parallel by default. To simulate the
agglomeration of children into hair wisps the "flatness" parameter is
now used to clump them together.

Cloth solver data for edit mode is unused, removed it.

Fix for scons files missing physics include folder.

Added separate damping for bending springs.

The bend damping factor was hardcoded to the same value as the stiffness.
Now it has its own factor in the settings and button in hair dynamics.

Set the length threshold for hair simulation to 10% again (from 1%).

With the default 5 substeps the simulation can otherwise still become
unstable. This is just a preliminary measure anyway until the length
variance can be fixed properly.

Fix for outdated root array size when changing the particle amount
during simulation.

Fix for hair chain testing in the cloth modifier.

Bending springs are en-bloc and not interleaved with other springs, so
this can't be used as a test for hair roots. Use consecutive indices
instead.