Previously, a GHash was used to store a flattened mapping of parent
information based on the Alembic hierarchy, and then that hash was used to
set parent pointers on Blender objects. This resulted in errors and
some duplicate objects. The new approach stores parent pointers while
traversing the Alembic hierarchy, which means that there is much more
information about the actual context of the Alembic object itself,
producing a more stable import.
Also replaced the bool param "to_yup" with "AbcAxisSwapMode mode", so that
it's more explicit that axes are swapped.
Also added unittests for create_swapped_rotation_matrix.
There was a problem with parent-child relations not getting set up
correctly when an Alembic object was both the transform for a mesh object
and the parent of other mesh objects.
convert_matrix() now only converts from Imath::M44d to float[4][4] (taking
different camera orientations into account). Import-time scaling is now
performed by the caller.
Also renamed AbcObjectReader::readObjectMatrix to
setupObjectTransform, as it does more than just reading the object
matrix; it also sets up an object constraint if the Alembic Xform is
animated.
Alembic is an interchange and caching format, that can contain custom
object schemas. Blender shouldn't crash (because of failing asserts) just
because it doesn't know such an object type.
It's a mapping from full path of an Alembic object to an AbcObjectReader*.
The fact that at some point it is used to construct parent-child relations
doesn't matter.
The importer was guessing whether an Alembic IXform object was part of a
child object, or should be represented as an Empty in Blender. By reversing
the order in which objects are visited, the children can now claim their
parent as part of the same object (so IPolyMesh claims its parent IXform
as part of the same Blender object). This results in much less guesswork.
I've also removed similar guesswork from the code that sets parent pointers,
by simply searching for the parent in a hierarchical way, instead of trying
to predict (again) which IXforms were turned into empties.
Also, visit_object() now actually visits the object -- previously it only
visited its children, and assumed the object it was called on was already
handled by a previous call.
create_transform_matrix(float[4][4]) did mostly the same as
create_transform_matrix(Object *, float[4][4]), but more elegant.
However, the former has some inconsistencies with the latter (which
are now merged and made explicit, turned out one was for z-up→y-up
while the other was for y-up→z-up), and was renamed to
copy_m44_axis_swap(...) to convey its purpose more clearly.
Furthermore, "loc" has been renamed to "trans", as matrices don't
store locations but translations; and more variables now have a src_
or dst_ prefix to denote whether they contain a matrix/vector in the
source or destination axis orientation.
AbcExporter::createTransformWriter() tries to predict the parent Xform
name, but if it cannot be found has multiple ways of creating it, possibly
under a different name than originally searched for.
The idea is to have a system where we properly log error messages and
let the users know that errors occured redirecting them to the console
for explanations. This is only implemented for the exporter since the
importer already has similar functionalities; however they shall
ultimately be unified in some way.
Reviewers: sybren, dfelinto
Differential Revision: https://developer.blender.org/D2541
