Blender Git Loki

LineArt: Remove modifiers access.

WIP: new UsdCameraReader class.

Also added logic to instantiate the camera reader
when traversing the USD stage. Not all camera
parameters are being set yet.

LineArt: Remove SceneLineArt.

LineArt: Move files to gpencil modifier folder.

fix crash when Group Output is not connected

Fix T82622: detect link cycles

Fix T82616: crash when using vector math node

apply changes and fixes from optimization branch

cleanup

Merge branch 'master' into outliner-cpp-refactor

support vertex weights in point distribute node

make point distribute node faster and more correct

cleanup: remove unneeded fixture; remove magic number.

restructure depsgraph object iterator

Merge branch 'master' into xr-actions-D9124

Merge branch 'master' into soc-2020-io-performance

XR: Implement XR grab operator

Transforms selected objects' location / rotation relative to a
controller's pose. Very basic compared to the existing transform
operators (which can also be used in VR via modal_3d), but provides
a more natural interaction in VR.

Exporter: start adding tests.

Corresponds to file https://developer.blender.org/F9260238

It should be put in "io_tests/blend_scene/all_objects_2_92.blend"
directory.

Cmake: add initial GTest support, placeholder file.

format