Blender Git Loki

Merging latest nv-usd-importer branch.

This includes merge from latest public Blender master
branch.

Merge branch 'usd-importer-T81257-merge' of https://gitlab-master.nvidia.com/omniverse/blender into nv-usd-importer

Merge branch 'master' of https://gitlab-master.nvidia.com/omniverse/blender into usd-importer-T81257-merge

Pulled latest from master branch.

Merge branch 'nv-usd-importer' of https://gitlab-master.nvidia.com/omniverse/blender into omniverse

Merge branch 'usd-importer-T81257-merge' of https://gitlab-master.nvidia.com/omniverse/blender into nv-usd-importer

USD importer: normals count bounds check.

Added bounds check for vertex varying normals, to
prevent crashes reading badly formed meshes, where
the number of normals doesn't match the number
of points. Also guarding against null mesh.

Merge branch 'usd_skel_export' of https://gitlab-master.nvidia.com/omniverse/blender into omniverse

USD armature export option off by default.

Since the Armature export feature is a not yet fully developed,
I labelled this option as experimental and disabled it by
default.

Change USD export option defaults.

Turn off vertex group and face map USD export
options by default, to reduce file size.

USD skel export format fixes.

USD skinned mesh export: set armature edit mode.

Updated USDSkinnedMeshWriter to enable the armature edit
mode to ensure mesh is saved in its rest position. This
seems to be more reliable than the previous code, which
was calling BKE_pose_where_is() on the armature object.

USD skel export: less verbose error output.

Now reporting out of bounds deform group indices
once per mesh.

USD export: write skinned mesh in rest position.

Updated the USDSkinnedMeshWriter to set the armature to
its rest position prior to writing mesh. This is
necessary to get the correct skeletal deformations.

USD import crash workaround.

Temporary workaround to prevent crash when reading
bezier curves. This is a placeholder until bezier
curves are properly supported.

USD skel export format fixes.

USD skel export: check div by zero.

Guarding against division by zero when normalizing joint
weights.

USD export: normalize skel joint weights.

Added logic to USDSkinnedMeshWriter to normalize joint weights.

USD skel export WIP.

Fixed armature export logic for writing pose channel
transform samples. Updated skinned mesh writer to
set the joint indices and joint weight attribute
element size to the maximum total weight value
of the deform verts.

USD export: write geom bind transform.

Extend skinned mesh writer to create the geom bind transform
attribute.