It was difficult to notice, but we weren't making use of the
`USDPrimReader::valid()` API calls during import.
In many(all?) cases this was fine as we would check the validity during
`read_object_data` or similar anyhow. Rather than just removing the API
entirely, this patch attempts to use it and has the following design:
- Where ever and whenever a reader is created, in addition to checking
null, we should now also check for `valid()` This happens in
`usd_capi_import` and `usd_reader_stage`.
- The `valid()` call is intended to check just the USD object status.
Blender object checks are handled elsewhere (same as they are
currently) since these objects are often not available at the time of
the call to `valid()`
This has the benefit that we at least know that USD is valid before our
heavy reading code ever starts executing. Some duplicate checks are now
removed.
Pull Request: https://projects.blender.org/blender/blender/pulls/129181
Added support for importing USD instanceable primitives into Blender
as collection instances.
Added a new USDInstanceReader class for importing USD
instances as Blender objects that instance collections containing
prototype data.
Extended the USDStageReader to read USD prototype prims into
collections that are instanced on the objects created by the instance
readers.
Removed the "Import Instance Proxies" import option.
Importing instances is enabled with a new "Scene Instancing" import
option, which is true by default. If this option is off, instances will be
imported as copies (which is the functionality previously enabled by
the "Import Instance Proxies" option).
Removed calls to UsdSkelBindingAPI::Apply() in the skeleton and
blend shape import code, as these calls were unnecessary and were
generating errors when importing instance prototypes with UsdSkel
data.
Nested instancing and animated prototypes are supported.
Pull Request: https://projects.blender.org/blender/blender/pulls/115076
This is an initial implementation of a USD importer.
This work is comprised of Tangent Animation's open source USD importer,
combined with features @makowalski had implemented.
The design is very similar to the approach taken in the Alembic
importer. The core functionality resides in a collection of "reader"
classes, each of which is responsible for converting an instance of a
USD prim to the corresponding Blender Object representation.
The flow of control for the conversion can be followed in the
`import_startjob()` and `import_endjob()` functions in `usd_capi.cc`.
The `USDStageReader` class is responsible for traversing the USD stage
and instantiating the appropriate readers.
Reviewed By: sybren, HooglyBoogly
Differential Revision: https://developer.blender.org/D10700
