The Alembic exporter has been restructured by leverages the
`AbstractHierarchyIterator` introduced by the USD exporter. The produced
Alembic files have not changed much (details below), as the Alembic
writing code has simply been moved from the old exporter to the new. How
the export hierarchy is handled changed a lot, though, and also the way
in which transforms are computed. As a result, T71395 is fixed.
Differences between the old and new exporter, in terms of the produced
Alembic file:
- Duplicated objects now have a unique numerical suffix.
- Matrices are computed differently, namely by simply computing the
evaluated transform of the object relative to the evaluated transform
of its export-parent. This fixes {T71395}, but otherwise should
produce the same result as before (but with simpler code).
Compared to the old Alembic exporter, Subdivision modifiers are now
disabled in a cleaner, more efficient way (they are disabled when
exporting with the "Apply Subdivisions" option is unchecked). Previously
the exporter would move to a new frame, disable the modifier, evaluate
the object, and enable the modifier again. This is now done before
exporting starts, and modifiers are only restored when exporting ends.
Some issues with the old Alembic exporter that have NOT been fixed in
this patch:
- Exporting NURBS patches and curves (see T49114 for example).
- Exporting flattened hierarchy in combination with dupli-objects. This
seems to be broken in the old Alembic exporter as well, but nobody
reported this yet.
Differential Revision: https://developer.blender.org/D7664
Reviewed By: Sergey
Blender now always exports transforms as as "inheriting", as Blender has
no concept of parenting without inheriting the transform.
Previously only objects with an actual parent were marked as
"inheriting", and parentless objects as "non-inheriting". However,
certain packages (for example USD's Alembic plugin) are incompatible
with non-inheriting transforms and will completely ignore such
transforms, placing all such objects at the world origin.
When importing non-inheriting transforms from Alembic, Blender will
break the parent-child relation and thus force the child to (correctly)
interpret the transform as world matrix.
Other types already had spaces, periods, and colons replaced by
underscores. The upcoming Alembic exporter (based on the
`AbstractHierarcyIterator` class) will be more consistent and apply the
same naming rules everywhere. This is in preparation for that change.
The `get_…_name()` functions in `abc_util.{cc,h}` will be removed then.
Previously the Alembic exporter exported a mesh object to
`{object.name}/{object.name}Shape`. Now it exports to
`{object.name}/{mesh.name}` instead. The same change also applies to
other object data types.
Note that the code now is a bit hackish, as `m_name` is set even in
cases where it isn't used. This hackishness was already there, though,
but it's now just more visible. This will all be cleaned up when the
Alembic exporter is ported to use the `AbstractHierarchyImporter`
structure of the Universal Scene Description (USD) exporter.
Reviewed By: mont29
Differential Revision: https://developer.blender.org/D7672
This was caused by a side-effect of our exporting code's memory
management (Alembic considers data "written" and "final" when its C++
objects go out of scope) in combination with my change in
rB65574463fa2d. I removed an "only export UVs on the first frame" clause
because it was unclear why this restriction was there. As it turns out,
it breaks the export of the 2nd and subsequent UV maps on an animated
mesh. Effectively, on every frame the Alembic library thought we want to
create a new UV map, instead of continuing to write a new frame of data
to the existing one.
This is resolved by keeping a reference to the C++ objects for the UV
maps in memory while the exporter is running.
CentOS on the buildbot still runs Python 3.6, which is also used for the
unit tests. This means that the tests can't use language features that
are available to Blender itself. And testing with a different version of
Python than will be used by the actual code seems like a bad idea to me.
This commit adds `TEST_PYTHON_EXECUTABLE` as advanced CMake option. This
will allow us to set a specific Python executable when we need it. When
not set, a platform-specific default will be used:
- On Windows, the `python….exe` from the installation directory. This is
just like before this patch, except that this patch adds the
overridability.
- On macOS/Linux, the `${PYTHON_EXECUTABLE}` as found by CMake.
Every platform should now have a value (configured by the user or
detected by CMake) for `TEST_PYTHON_EXE`, so there is no need to allow
running without. This also removes the need to have some Python files
marked as executable.
If `TEST_PYTHON_EXE` is not user-configured, and thus the above default
is used, a status message is logged by CMake. I've seen this a lot in
other projects, and I like that it shows which values are auto-detected.
However, it's not common in Blender, so if we want we can either remove
it now, or remove it after the buildbot has been set up correctly.
Differential Revision: https://developer.blender.org/D7395
Reviewed by: campbellbarton, mont29, sergey
The ABC_export and ABC_import functions both take a as_background_job
parameter, and return a boolean.
When as_background_job=true, returns false immediately after scheduling
a background job. This was the old behaviour of this function, which makes
it very hard for scripts to do something with the data after the import
or export completes.
When as_background_job=false, performs the export synchronously, and
returns true when the export was ok, and false if there were any errors.
This allows further processing.
The Scene.alembic_export() function is deprecated, and will be removed from
Blender 2.8 in favour of calling the bpy.ops.wm.alembic_export() operator.
As such, it has been hard-coded to the old background job behaviour.
The export is still slower than needed, as the particle systems themselves
aren't disabled during the export. It's only the writing to the Alembic
file that's skipped.
Curve resolution isn't natively supported by Alembic, hence it is stored
in a user property "blender:resolution". I've looked at a Maya curves
example file, but that also didn't contain any information about curve
resolution.
Differential Revision: https://developer.blender.org/D2634
Reviewers: kevindietrich
The order number written to Alembic is the same as we use in memory, so
the +1 wasn't needed, at least according to the reference Maya exporter
maya/AbcExport/MayaNurbsCurveWriter.cpp, function
MayaNurbsCurveWriter::write(), in the Alembic source code.
Furthermore, when writing an array of nurb orders, the curve type should
be set to kVariableOrder, otherwise the importer will ignore it.
This test checks that a set of cubes are exported with the correct
transform, both with flatten=True and flatten=False.
This commit also adds an easy to use superclass for upcoming Alembic
unit tests.
