Blender Git Loki

Use a consistent number of RNG steps in both sample generation and skipping.

This is to ensure that threaded generator usage creates the exact same results
as the non-threaded base version. Further improvements and testing will be
needed.

Multithreading support for the mesh sampling library.

Samples can be generated either one-by-one using the existing "make_sample"
function (which uses a default context), or use the more efficient batch
generation functions. These optionally support threading via the task scheduler
now.

Fix hair follicle array write/read.

Merge branch 'blender2.8' into strand_editmode

Removed unused shaders in the draw modes module.

Implement control strands generation for basic hair types along surface normals.

The default hair group type uses vertex normals to generate guide strands automatically.

Store the scalp mesh as part of the hair drawing interface.

The scalp mesh is always needed for evaluating root positions anyway.

Removed fiber drawing from the strand edit mode to simplify code.

For rendering hair fibers the edit mode should just use the underlying data.

Hair drawing data based on the new DNA hair groups.

Store pointer into the hair follicle array in hair groups directly.

This creates a dependency of the hair groups on the validity of the pattern,
so care has to be taken to always update the groups when the pattern changes.

Split off hair drawing code into a separate file.

List of 'Hair Groups' in hair patterns that will generate actual fibers for rendering.

Each group affects a subset of the hair follicles, so that multiple effects can be combined
without overlapping sample sets.

Merge branch 'blender2.8' of git.blender.org:blender into strand_editmode

Operator for generating a hair follicle distribution.

DNA data + modifier for storing persistent hair data.

This stores basic hair follicle data, rather than full fiber caches
(which should only be generated for render data).

Note that deformation by strands will just be one possible way to generate
hair fibers, so strands should be kept separate from the hair follicle data somewhat.

Prototype hair deformers for generated detail like clumping and curling.

Currently only clumping and curls are implemented. There is no proper input
for the parameters yet, these are just hardcoded atm. Eventually the hair system
should either define uniform values from hair system settings or enable per-fiber
values using a material or other node-based input.

Some optional timing for strand data buffer construction.

Subdivision of hair fibers for smoother shading.

Subdivision works on the parent strands for efficiency. The fibers lengths
are based on the final subdivided length of parents, so no changes to the
shader are required.

This would be nicer with a tesselation shader, but this feature is not
available in Blender 2.8.

Use a 2D texture for the hair interpolation data instead of 1D for larger number of hairs.

It turns out that 1D textures have the same size limit on their 1 axis as 2D textures.
This limits the potential number of hair dramatically, even though the actual size of
the texture is very small. Using a 2D texture and wrapping the index avoids this problem.

Default settings for hair edit mode tool settings.