USD: add USD importer

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

1 files changed, 0 insertions, 9 deletions

diff --git a/source/blender/io/alembic/intern/abc_util.h b/source/blender/io/alembic/intern/abc_util.h
index 98f4b0376a7..ced9fde0f85 100644
--- a/source/blender/io/alembic/intern/abc_util.h
+++ b/source/blender/io/alembic/intern/abc_util.h
@@ -22,15 +22,6 @@
 #include <Alembic/Abc/All.h>
 #include <Alembic/AbcGeom/All.h>
 
-/**
- * \brief The CacheReader struct is only used for anonymous pointers,
- * to interface between C and C++ code. This library only creates
- * pointers to AbcObjectReader (or subclasses thereof).
- */
-struct CacheReader {
-  int unused;
-};
-
 using Alembic::Abc::chrono_t;
 
 struct ID;