Blender Git Loki

Cleanup: Remove BLI_ prefix from listbase macro

This is kind of doesn't matter where macro itself is defined.

We should stick to the following:

- If some macro is actually more an inline function, follow regular
function name conventions.
- If macro is a macro, type it in capitals. Use module prefix if that
helps readability or it if helps avoiding accidents.

Merge branch 'master' into blender2.8

Simple hair children: Make twist affected by texture

This completes twist feature, which is now possible to also control by
texture. Since textures can not easily contain negative values as well,
same trick with 0.5 neutral as vertex groups is used.

All in all, this twist features allows to do following things.

Original hair:

{F2287535}

Hair with scientifically calculated twist value of 0.5:

{F2287540}

And we can also twist braids in opposite directions dependent on left/right
side:

{F2287548}

Fix T54078: Adding subsurf prior to particle system breaks simple children vgroups and textures

cpa->num points to a face index on BASE mesh, but get_child_modifier_parameters()
expects index on a FINAL dm. So wrong index was used here.

Simple hair children: Make twist affected by vertex group

The idea is to give a control over direction of twist, and maybe amount of
twist as well. More concrete example: make braids on left and right side of
character head to be twisting opposite directions.

Now, tricky part: we need some negative values to flip direction, but weights
can not be negative. So we use same trick as displacement map and tangent normal
maps, where 0.5 is neutral, values below 0.5 are considered negative and values
above 0.5 are considered positive.

Simple hair children: Initial implementation of twist control

It allows to have children hair to be twisted around parent curve, which is
quite an essential feature when creating hair braids.

There are currently two controls:

- Number of turns around parent children.
- Influence curve, which allows to modify "twistness" along the strand.

Blenlib: Assert when attempting to rotate point around vector and store result in the point

This isn't supported since there are subsequent reads to all point coordinates
after modification started.

Probably we need to create a temp copy of point, but that's like extra CPU
ticks.

Particles: Wrap insane amount of arguments to child modifier evaluation

Use single structure. It seems we will need to pass more information soon,
so better to do it via the structure.

Avoid unnecessary sqrt calls

Fix merge error

The line must be after grease pencil code

Merge branch 'blender2.8' into greasepencil-object

Conflicts:
source/blender/draw/intern/draw_manager.c

Fix crash when rendering particles with cycles

view_layer is NULL when the render engine is created, this gets passed
around and ends up in this code causing a crash. This should be reverted
after the render engine api is updated to set view_layer.

Make particle edit draw mode a noop

Seems this was just a template, but that template painted everything
green. Not sure what this draw mode should do really.

Fix lack of particles updates and disappearing particles

The conditionals in particle code are... some sort of madness... I'm not
even sure what the correct behavior should be from looking at it.

In this case the path cache generation was being skipped in edit mode.

Tag update when using particle edit brushes

Fix crash with particle cut brush and other brushes

Why is bedit->data.context NULL?

Start bringing back particle edit

Its kind of broken, but have to start somewhere

Add versioning code to make particles with default size visible again

Due to changes in draw code particles from old files that may have had a
default draw size of 0 will not be visible. Old draw code would check
for this and adjust the size, however the unit for draw size has changed
from pixels to BU, and it no longer makes sense to have such checks.

This patch is to ensure particles from such files remain visible.

Merge branch 'master' into blender2.8

Cleanup: style, warning