Blender Git Commits

Pampering the stupid MSVC compiler again, it fails to build valid C code.

Added new header for Eigen utility classes.

These make passing data between Eigen vector and matrix types and plain
C arrays more convenient.

Updated a few comments.

Compile hair volumetrics code as C++, so we can use Eigen easier.

Minor debug code fix.

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

Use a fixed, uniform cell size for hair continuum grids.

This is a bit more awkward for artists to use, but necessary for
a stable solution of the hair continuum calculation. The grid size is
defined by the user, the extent of the grid is then calculated based on
the hair geometry. A hard upper limit prevents bad memory allocation
in case too small values are entered.

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

Removed unused voxel_filter_size DNA property.

This is an artifact of earlier attempts to implement velocity smoothing,
but doesn't work anyway.

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

Renamed HairVertexGrid to HairGrid, since it's not actually storing
hair vertex data.

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

Removed unused "collider grid" struct from hair volumetrics.

This is a leftover from previous approach of hair collisions (with
insufficient results). The hair volumetrics actually implements
"collision" with solid objects as well, but uses a Neumann boundary
condition on the main grid for this purpose.

Better grid rasterization method for hair volumetric grids.

This is based on the paper
"Detail Preserving Continuum Simulation of Straight Hair"
(McAdams, Selle, Ward, 2009)

The main difference is that hair line segments are used rather than only
rasterizing velocity at the vertices. This gives a much better coverage
of the hair volume grid, otherwise gaps can be produced at smaller grid
cell sizes and the distribution is uneven along the hair curve.

The algorithm for rasterizing is a variation of Bresenham's algorithm
extended onto 3D grids.

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

New debug element "circle" for simulations, which is quite useful for
visualizing scalar fields.

Debug grid drawing for hair volume was drawing one subdivision too many.

Unused leftover debug variable.

Reimplemented the voxel texture type for displaying hair continuum grids.

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

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.

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

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)

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