Blender Git Commits

IO: Allow exporting a subset of the writers

This is in order to prepare for compatibility with the Alembic exporter. That exporter is capable of writing object transforms and object data at different (sub)frames.

The rename from `created_writers` to `used_writers` is necessary, as not all created writers will be actually used in each iteration.

Differential Revision: https://developer.blender.org/D7670

Remove unnecessary include directories from CMakeLists.txt

IO: Move Abstract Hierarchy Iterator into `io/common`

The goal of the `AbstractHierarchyIterator` class (and supporting classes) was to use it in different exporters. It shouldn't be part of the USD module + namespace any more.

The source files are moved into `io/common`, which is compiled & linked into a new library `bf_io_common`. The unittests are still inside the `tests/gtests/usd` directory. They should be moved to a separate test module too, but that will be delayed until after T73268 has been resolved.

Differential Revision: https://developer.blender.org/D7669

Merge branch 'master' into panel-list-patch

Review feedback

Merge branch 'master' into greasepencil-object

Merge branch 'master' into greasepencil-object

Merge branch 'master' into panel-list-patch

Cleanup: Alembic, refactored flattened export

The AbstractHierarchyIterator has been simplified & refactored, such that
it is possible for a subclass to change the export hierarchy. This makes
the Alembic exporter responsible for the "flattening", which is appropriate
as the USD exporter doesn't even have this export option.

No functional changes.

Alembic: when exporting flattened, always check parent for animation

When exporting to a flattened "hierarchy", the animation of the parent
(in Blender) will not be known to the Alembic file. In this case,
whenever an object is moving, it needs to be treated as animated, even
when it's through the animation of its parent.

Alembic: Updated tests to reflect the current exporter

The differences:
- The old exporter always exported a mesh object to
`{object.name}/{object.name}Shape`. Now it exports to
`{object.name}/{mesh.name}` instead.
- Duplicated objects now have a unique numerical suffix.
- Transforms are always exported as inheriting, because Blender doesn't
have a concept of parenting without inheriting the transform.

Alembic: added ability to export as flattened hierarchy

I'm not entirely happy that this invades into the `AbstractHierarchyIterator`
class, so I might revisit this later.

Merge remote-tracking branch 'origin/master' into temp-alembic-exporter-T73363-ms2

Merge branch 'master' into greasepencil-object

Conflicts:
release/scripts/startup/bl_ui/properties_grease_pencil_common.py
release/scripts/startup/bl_ui/space_view3d_toolbar.py
source/blender/makesrna/intern/rna_brush.c

Merge branch 'master' into greasepencil-object

Merge branch 'master' into greasepencil-object

Merge branch 'master' into greasepencil-object

merge master and fix issues

Cycles: attempt to avoid OpenCL symbol conflicts with RTLD_DEEPBIND

Fix particles colliding twice because they didn't have time to move