Blender Git Commits

Fix some issues, improve error message

Fixes:
* Destruct surface when destroying session on error. Fixes null pointer
dereference when trying to draw the surface on next redraw.
* Fix trying to enable same extensions/API-layers multiple times due to
static array usage not being cleared after error.
* Null pointer dereference with OpenGL drawing

Add a visibility flag for time node

This should help to reduce computation overhead for non time node

Merge branch 'master' into greasepencil-object

LANPR: Moved lanpr_util.c into ED.

LANPR: Moved non-drawing related chaining code to ED.

LANPR: Fixing local functions.

LANPR: Fixing local function and naming.

LANPR: Moved CPU side calculations to ED.

LANPR: Line layer operators now moved to ED

LANPR: Changed to ED_ prefix.

LANPR: Move GPencil operators into ED

Merge remote-tracking branch 'origin/master' into soc-2019-npr

Fix crash on OpenXR error before context is created fully

Show useful error reports in case of errors.

E.g. with an active OpenXR runtime installed, but no HMD plugged in,
Blender will now show: "Failed to get device information. Is a device
plugged in?".
In case of such errors, the VR-session will be cleanly exited, with
no side effects to the rest of Blender (at least if there are no bugs).

The GHOST_Xr API now allows setting a custom error handling callback
which may cleanly destroy all GHOST_Xr data.

[Fast import/export] Added proper material support

[Fast import/export] Fixed index of normals

USD: added USD export to the File > Export menu

This also required exposing the build option `bpy.app.build_options.usd`.

USD: Avoid writing invisible particle emitter meshes

USD: Offer choice for viewport or render settings

The exporter operator now takes a parameter to choose the depsgraph
evaluation mode (Viewport/Render). This makes it easier to switch between
exporting particle hair (Render) or mesh hair (Viewport).

Merge branch 'master' into functions