Blender Git Loki

WIP: Render mixing GP and Eevee or Cycles

Still there are problems with AA, but now it's possible to get a composed result with Cycle/Eevee and Grease Pencil.

Cycles: add random walk subsurface scattering to Principled BSDF.

Differential Revision: https://developer.blender.org/D3054

Cycles: random walk subsurface scattering.

It is basically brute force volume scattering within the mesh, but part
of the SSS code for faster performance. The main difference with actual
volume scattering is that we assume the boundaries are diffuse and that
all lighting is coming through this boundary from outside the volume.

This gives much more accurate results for thin features and low density.
Some challenges remain however:

* Significantly more noisy than BSSRDF. Adding Dwivedi sampling may help
here, but it's unclear still how much it helps in real world cases.
* Due to this being a volumetric method, geometry like eyes or mouth can
darken the skin on the outside. We may be able to reduce this effect,
or users can compensate for it by reducing the scattering radius in
such areas.
* Sharp corners are quite bright. This matches actual volume rendering
and results in some other renderers, but maybe not so much real world
objects.

Differential Revision: https://developer.blender.org/D3054

Temp fix for object mode

The function ED_object_base_activate() was calling again the mode set and undo the mode change.

Do we need this function? Really the object is already the active one.

Fix infinite loop in mode set

The mode set entered in an infinite loop

inner material is part of presets now

Merge branch 'blender2.8' into asset-engine

Merge branch 'master' into blender2.8

Fix (unreported) error on freeing timers which customdata pointer shall not be freed.

Looks like there was no way to avoid that so far, since
WM_event_add_timer_notifier can set mere int-in-pointer there, this can
cause issues. So added mere flags system to wmTimer to allow
controlling this.

Fix compiler error after merge

Fix on previous commit to use active_object

Need to use active_object, not object

Fix python object mode changes

After last changes, need to use workspace mode

Merge branch 'blender2.8' into greasepencil-object

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

Merge branch 'blender2.8' into asset-engine

Merge branch 'master' into blender2.8

Fix (unreported) crash when duplicating a FileBrowser window in preview draw mode.

We did not clear preview or smoothscroll timers pointers in copy code...

Fix (unreported) crash when duplicating a FileBrowser window in preview draw mode.

We did not clear preview or smoothscroll timers pointers in copy code...

Merge branch 'blender2.8' into asset-engine

Merge branch 'master' into blender2.8

Doc: attempt to document RNA's FunctionFlag.

Tired of searching through code to find which is what, and how to use it
in the C callback, everytime I need anot-so-common option...