Blender Git Loki

Revert "Take out two of Lukas's optimizations in the Bessel function"

Turns out this wasn't needed.

This reverts commit 11633e89b6ead2fd497630f50c93863134fff74f.

Apologies, I didn't complete the defaults properly!

Ref T54796

Use Benedikt Bitterli's and PBRT's sane defaults

This should give brownish hair, implemented with pheomelanin.

Defaults:
- Color: Blender's default gray
- Melanin: Eumelanin 0, Pheomelanin 1.3
- Absorption coefficient: 1.3*d'Eon's pheomelanin mapping (brown hair)
- Offset: 2�
- Roughness: 0.3 in both directions
- Primary Reflection Roughness: 1.0 (fully enabled)
- IOR: 1.55

Ref T54796

Take out two of Lukas's optimizations in the Bessel function

In case they're bringing in additional bugs

Ref T54796

Lift max value in Melanin sockets

I honestly don't know how d'Eon's mapping work.
I'll ask him then come back to this bit of code.

Ref T54796

Cleanup: missing parentheses

Indent typo in the node update

Give the Absorption coefficient its own socket

Ref T54796

Allow using the Color socket for all parametrizations except Direct coloring

Ref T54796

Add separate sockets for managing melanin coefficients

This patch follows Arnold's nomenclature UI-side
(Melanin = Eumelanin, Melanin Redness = Pheomelanin)

This also disables the relevant sockets when changing parametrizations.

Ref T54796

Clarify one of the parameters

(RoughnessU and RoughnessV are still there because other nodes use them too.)

Ref T54796

Make use of our customized OSL allocator

Ref T54796

Add some help tooltips to the shader

Ref T54796

Merge branch 'master' into soc-2018-hair-shader

Week 3's merge: no issues

Initialize the default color parameterization

Ref T54796

Fix wrong min/max range for primary reflection roughness.

Fix hair shader not working in final render.

Copy geometry data when allocating the OSL shader closure

This may fix https://blenderartists.org/t/cycless-gsoc-2018-project-new-hair-shader-expectations/1103070/25.
However, I didn't run into it in MacOS or Windows, w/ OSL, CPU, or CUDA.

Ref T54796

Enable blur on primary reflection roughness too

Ref T54796

Access primary reflection roughness via cycles's stack

Ref T54796