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, 100 insertions, 0 deletions

diff --git a/source/blender/io/usd/intern/usd_reader_camera.cc b/source/blender/io/usd/intern/usd_reader_camera.cc
new file mode 100644
index 00000000000..2732ed5770d
--- /dev/null
+++ b/source/blender/io/usd/intern/usd_reader_camera.cc
@@ -0,0 +1,100 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Adapted from the Blender Alembic importer implementation.
+ *
+ * Modifications Copyright (C) 2021 Tangent Animation.
+ * All rights reserved.
+ */
+
+#include "usd_reader_camera.h"
+
+#include "DNA_camera_types.h"
+#include "DNA_object_types.h"
+
+#include "BKE_camera.h"
+#include "BKE_object.h"
+
+#include "BLI_math.h"
+
+#include <pxr/pxr.h>
+#include <pxr/usd/usdGeom/camera.h>
+
+namespace blender::io::usd {
+
+void USDCameraReader::create_object(Main *bmain, const double /* motionSampleTime */)
+{
+  Camera *bcam = static_cast<Camera *>(BKE_camera_add(bmain, name_.c_str()));
+
+  object_ = BKE_object_add_only_object(bmain, OB_CAMERA, name_.c_str());
+  object_->data = bcam;
+}
+
+void USDCameraReader::read_object_data(Main *bmain, const double motionSampleTime)
+{
+  Camera *bcam = (Camera *)object_->data;
+
+  pxr::UsdGeomCamera cam_prim(prim_);
+
+  if (!cam_prim) {
+    return;
+  }
+
+  pxr::VtValue val;
+  cam_prim.GetFocalLengthAttr().Get(&val, motionSampleTime);
+  pxr::VtValue verApOffset;
+  cam_prim.GetVerticalApertureOffsetAttr().Get(&verApOffset, motionSampleTime);
+  pxr::VtValue horApOffset;
+  cam_prim.GetHorizontalApertureOffsetAttr().Get(&horApOffset, motionSampleTime);
+  pxr::VtValue clippingRangeVal;
+  cam_prim.GetClippingRangeAttr().Get(&clippingRangeVal, motionSampleTime);
+  pxr::VtValue focalDistanceVal;
+  cam_prim.GetFocusDistanceAttr().Get(&focalDistanceVal, motionSampleTime);
+  pxr::VtValue fstopVal;
+  cam_prim.GetFStopAttr().Get(&fstopVal, motionSampleTime);
+  pxr::VtValue projectionVal;
+  cam_prim.GetProjectionAttr().Get(&projectionVal, motionSampleTime);
+  pxr::VtValue verAp;
+  cam_prim.GetVerticalApertureAttr().Get(&verAp, motionSampleTime);
+  pxr::VtValue horAp;
+  cam_prim.GetHorizontalApertureAttr().Get(&horAp, motionSampleTime);
+
+  bcam->lens = val.Get<float>();
+  /* TODO(makowalski) */
+#if 0
+   bcam->sensor_x = 0.0f;
+   bcam->sensor_y = 0.0f;
+#endif
+  bcam->shiftx = verApOffset.Get<float>();
+  bcam->shifty = horApOffset.Get<float>();
+
+  bcam->type = (projectionVal.Get<pxr::TfToken>().GetString() == "perspective") ? CAM_PERSP :
+                                                                                  CAM_ORTHO;
+
+  /* Calling UncheckedGet() to silence compiler warnings. */
+  bcam->clip_start = max_ff(0.1f, clippingRangeVal.UncheckedGet<pxr::GfVec2f>()[0]);
+  bcam->clip_end = clippingRangeVal.UncheckedGet<pxr::GfVec2f>()[1];
+
+  bcam->dof.focus_distance = focalDistanceVal.Get<float>();
+  bcam->dof.aperture_fstop = static_cast<float>(fstopVal.Get<float>());
+
+  if (bcam->type == CAM_ORTHO) {
+    bcam->ortho_scale = max_ff(verAp.Get<float>(), horAp.Get<float>());
+  }
+
+  USDXformReader::read_object_data(bmain, motionSampleTime);
+}
+
+}  // namespace blender::io::usd