Alembic: new exporter based on the USD exporter structure

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

4 files changed, 124 insertions, 105 deletions

diff --git a/tests/gtests/alembic/CMakeLists.txt b/tests/gtests/alembic/CMakeLists.txt
index 6ba1c4465d9..90f1829fc77 100644
--- a/tests/gtests/alembic/CMakeLists.txt
+++ b/tests/gtests/alembic/CMakeLists.txt
@@ -24,6 +24,8 @@ set(INC
   ../../../source/blender/blenlib
   ../../../source/blender/blenkernel
   ../../../source/blender/io/alembic
+  ../../../source/blender/io/common
+  ../../../source/blender/io/usd/intern
   ../../../source/blender/makesdna
   ../../../source/blender/depsgraph
   ${ALEMBIC_INCLUDE_DIRS}
diff --git a/tests/gtests/alembic/abc_export_test.cc b/tests/gtests/alembic/abc_export_test.cc
index 2926809a1af..cdc98178550 100644
--- a/tests/gtests/alembic/abc_export_test.cc
+++ b/tests/gtests/alembic/abc_export_test.cc
@@ -1,11 +1,12 @@
 #include "testing/testing.h"
 
 // Keep first since utildefines defines AT which conflicts with STL
-#include "exporter/abc_exporter.h"
+#include "exporter/abc_archive.h"
 #include "intern/abc_util.h"
 
 extern "C" {
 #include "BKE_main.h"
+#include "BLI_fileops.h"
 #include "BLI_math.h"
 #include "BLI_utildefines.h"
 #include "DNA_scene_types.h"
@@ -13,140 +14,150 @@ extern "C" {
 
 #include "DEG_depsgraph.h"
 
-using namespace blender::io::alembic;
-
-class TestableAbcExporter : public AbcExporter {
- public:
-  TestableAbcExporter(Main *bmain, const char *filename, ExportSettings &settings)
-      : AbcExporter(bmain, filename, settings)
-  {
-  }
-
-  void getShutterSamples(unsigned int nr_of_samples,
-                         bool time_relative,
-                         std::vector<double> &samples)
-  {
-    AbcExporter::getShutterSamples(nr_of_samples, time_relative, samples);
-  }
-
-  void getFrameSet(unsigned int nr_of_samples, std::set<double> &frames)
-  {
-    AbcExporter::getFrameSet(nr_of_samples, frames);
-  }
-};
+namespace blender {
+namespace io {
+namespace alembic {
 
 class AlembicExportTest : public testing::Test {
  protected:
-  ExportSettings settings;
+  ABCArchive *abc_archive;
+
+  AlembicExportParams params;
   Scene scene;
   Depsgraph *depsgraph;
-  TestableAbcExporter *exporter;
   Main *bmain;
 
   virtual void SetUp()
   {
-    settings.frame_start = 31.0;
-    settings.frame_end = 223.0;
+    abc_archive = nullptr;
 
     /* Fake a 25 FPS scene with a nonzero base (because that's sometimes forgotten) */
     scene.r.frs_sec = 50;
     scene.r.frs_sec_base = 2;
+    strcpy(scene.id.name, "SCTestScene");
 
     bmain = BKE_main_new();
 
     /* TODO(sergey): Pass scene layer somehow? */
     ViewLayer *view_layer = (ViewLayer *)scene.view_layers.first;
-    settings.depsgraph = depsgraph = DEG_graph_new(bmain, &scene, view_layer, DAG_EVAL_VIEWPORT);
-
-    settings.scene = &scene;
-    settings.view_layer = view_layer;
-
-    exporter = NULL;
+    depsgraph = DEG_graph_new(bmain, &scene, view_layer, DAG_EVAL_RENDER);
   }
 
   virtual void TearDown()
   {
     BKE_main_free(bmain);
     DEG_graph_free(depsgraph);
-    delete exporter;
+    deleteArchive();
+  }
+
+  // Call after setting up the parameters.
+  void createArchive()
+  {
+    if (abc_archive != nullptr) {
+      deleteArchive();
+    }
+    abc_archive = new ABCArchive(bmain, &scene, params, "somefile.abc");
   }
 
-  // Call after setting up the settings.
-  void createExporter()
+  void deleteArchive()
   {
-    exporter = new TestableAbcExporter(bmain, "somefile.abc", settings);
+    delete abc_archive;
+    if (BLI_exists("somefile.abc")) {
+      BLI_delete("somefile.abc", false, false);
+    }
+    abc_archive = nullptr;
   }
 };
 
-TEST_F(AlembicExportTest, TimeSamplesFullShutter)
+TEST_F(AlembicExportTest, TimeSamplesFullShutterUniform)
 {
-  settings.shutter_open = 0.0;
-  settings.shutter_close = 1.0;
-
-  createExporter();
-  std::vector<double> samples;
-
-  /* test 5 samples per frame */
-  exporter->getShutterSamples(5, true, samples);
-  EXPECT_EQ(5, samples.size());
-  EXPECT_NEAR(1.240, samples[0], 1e-5f);
-  EXPECT_NEAR(1.248, samples[1], 1e-5f);
-  EXPECT_NEAR(1.256, samples[2], 1e-5f);
-  EXPECT_NEAR(1.264, samples[3], 1e-5f);
-  EXPECT_NEAR(1.272, samples[4], 1e-5f);
-
-  /* test same, but using frame number offset instead of time */
-  exporter->getShutterSamples(5, false, samples);
-  EXPECT_EQ(5, samples.size());
-  EXPECT_NEAR(0.0, samples[0], 1e-5f);
-  EXPECT_NEAR(0.2, samples[1], 1e-5f);
-  EXPECT_NEAR(0.4, samples[2], 1e-5f);
-  EXPECT_NEAR(0.6, samples[3], 1e-5f);
-  EXPECT_NEAR(0.8, samples[4], 1e-5f);
-
-  /* use the same setup to test getFrameSet() */
-  std::set<double> frames;
-  exporter->getFrameSet(5, frames);
-  EXPECT_EQ(965, frames.size());
-  EXPECT_EQ(1, frames.count(31.0));
-  EXPECT_EQ(1, frames.count(31.2));
-  EXPECT_EQ(1, frames.count(31.4));
-  EXPECT_EQ(1, frames.count(31.6));
-  EXPECT_EQ(1, frames.count(31.8));
+  /* Test 5 samples per frame, for 2 frames. */
+  params.shutter_open = 0.0;
+  params.shutter_close = 1.0;
+  params.frame_start = 31.0;
+  params.frame_end = 32.0;
+  params.frame_samples_xform = params.frame_samples_shape = 5;
+  createArchive();
+  std::vector<double> frames(abc_archive->frames_begin(), abc_archive->frames_end());
+  EXPECT_EQ(10, frames.size());
+  EXPECT_NEAR(31.0, frames[0], 1e-5);
+  EXPECT_NEAR(31.2, frames[1], 1e-5);
+  EXPECT_NEAR(31.4, frames[2], 1e-5);
+  EXPECT_NEAR(31.6, frames[3], 1e-5);
+  EXPECT_NEAR(31.8, frames[4], 1e-5);
+  EXPECT_NEAR(32.0, frames[5], 1e-5);
+  EXPECT_NEAR(32.2, frames[6], 1e-5);
+  EXPECT_NEAR(32.4, frames[7], 1e-5);
+  EXPECT_NEAR(32.6, frames[8], 1e-5);
+  EXPECT_NEAR(32.8, frames[9], 1e-5);
+
+  for (double frame : frames) {
+    EXPECT_TRUE(abc_archive->is_xform_frame(frame));
+    EXPECT_TRUE(abc_archive->is_shape_frame(frame));
+  }
+}
+
+TEST_F(AlembicExportTest, TimeSamplesFullShutterDifferent)
+{
+  /* Test 3 samples per frame for transforms, and 2 per frame for shapes, for 2 frames. */
+  params.shutter_open = 0.0;
+  params.shutter_close = 1.0;
+  params.frame_start = 31.0;
+  params.frame_end = 32.0;
+  params.frame_samples_xform = 3;
+  params.frame_samples_shape = 2;
+  createArchive();
+  std::vector<double> frames(abc_archive->frames_begin(), abc_archive->frames_end());
+  EXPECT_EQ(8, frames.size());
+  EXPECT_NEAR(31.0, frames[0], 1e-5);  // transform + shape
+  EXPECT_TRUE(abc_archive->is_xform_frame(frames[0]));
+  EXPECT_TRUE(abc_archive->is_shape_frame(frames[0]));
+  EXPECT_NEAR(31.33333, frames[1], 1e-5);  // transform
+  EXPECT_TRUE(abc_archive->is_xform_frame(frames[1]));
+  EXPECT_FALSE(abc_archive->is_shape_frame(frames[1]));
+  EXPECT_NEAR(31.5, frames[2], 1e-5);  // shape
+  EXPECT_FALSE(abc_archive->is_xform_frame(frames[2]));
+  EXPECT_TRUE(abc_archive->is_shape_frame(frames[2]));
+  EXPECT_NEAR(31.66666, frames[3], 1e-5);  // transform
+  EXPECT_TRUE(abc_archive->is_xform_frame(frames[3]));
+  EXPECT_FALSE(abc_archive->is_shape_frame(frames[3]));
+  EXPECT_NEAR(32.0, frames[4], 1e-5);  // transform + shape
+  EXPECT_TRUE(abc_archive->is_xform_frame(frames[4]));
+  EXPECT_TRUE(abc_archive->is_shape_frame(frames[4]));
+  EXPECT_NEAR(32.33333, frames[5], 1e-5);  // transform
+  EXPECT_TRUE(abc_archive->is_xform_frame(frames[5]));
+  EXPECT_FALSE(abc_archive->is_shape_frame(frames[5]));
+  EXPECT_NEAR(32.5, frames[6], 1e-5);  // shape
+  EXPECT_FALSE(abc_archive->is_xform_frame(frames[6]));
+  EXPECT_TRUE(abc_archive->is_shape_frame(frames[6]));
+  EXPECT_NEAR(32.66666, frames[7], 1e-5);  // transform
+  EXPECT_TRUE(abc_archive->is_xform_frame(frames[7]));
+  EXPECT_FALSE(abc_archive->is_shape_frame(frames[7]));
 }
 
 TEST_F(AlembicExportTest, TimeSamples180degShutter)
 {
-  settings.shutter_open = -0.25;
-  settings.shutter_close = 0.25;
-
-  createExporter();
-  std::vector<double> samples;
-
-  /* test 5 samples per frame */
-  exporter->getShutterSamples(5, true, samples);
-  EXPECT_EQ(5, samples.size());
-  EXPECT_NEAR(1.230, samples[0], 1e-5f);
-  EXPECT_NEAR(1.234, samples[1], 1e-5f);
-  EXPECT_NEAR(1.238, samples[2], 1e-5f);
-  EXPECT_NEAR(1.242, samples[3], 1e-5f);
-  EXPECT_NEAR(1.246, samples[4], 1e-5f);
-
-  /* test same, but using frame number offset instead of time */
-  exporter->getShutterSamples(5, false, samples);
-  EXPECT_EQ(5, samples.size());
-  EXPECT_NEAR(-0.25, samples[0], 1e-5f);
-  EXPECT_NEAR(-0.15, samples[1], 1e-5f);
-  EXPECT_NEAR(-0.05, samples[2], 1e-5f);
-  EXPECT_NEAR(0.05, samples[3], 1e-5f);
-  EXPECT_NEAR(0.15, samples[4], 1e-5f);
-
-  /* Use the same setup to test getFrameSet().
-   * Here only a few numbers are tested, due to rounding issues. */
-  std::set<double> frames;
-  exporter->getFrameSet(5, frames);
-  EXPECT_EQ(965, frames.size());
-  EXPECT_EQ(1, frames.count(30.75));
-  EXPECT_EQ(1, frames.count(30.95));
-  EXPECT_EQ(1, frames.count(31.15));
+  /* Test 5 samples per frame, for 2 frames. */
+  params.shutter_open = -0.25;
+  params.shutter_close = 0.25;
+  params.frame_start = 31.0;
+  params.frame_end = 32.0;
+  params.frame_samples_xform = params.frame_samples_shape = 5;
+  createArchive();
+  std::vector<double> frames(abc_archive->frames_begin(), abc_archive->frames_end());
+  EXPECT_EQ(10, frames.size());
+  EXPECT_NEAR(31 - 0.25, frames[0], 1e-5);
+  EXPECT_NEAR(31 - 0.15, frames[1], 1e-5);
+  EXPECT_NEAR(31 - 0.05, frames[2], 1e-5);
+  EXPECT_NEAR(31 + 0.05, frames[3], 1e-5);
+  EXPECT_NEAR(31 + 0.15, frames[4], 1e-5);
+  EXPECT_NEAR(32 - 0.25, frames[5], 1e-5);
+  EXPECT_NEAR(32 - 0.15, frames[6], 1e-5);
+  EXPECT_NEAR(32 - 0.05, frames[7], 1e-5);
+  EXPECT_NEAR(32 + 0.05, frames[8], 1e-5);
+  EXPECT_NEAR(32 + 0.15, frames[9], 1e-5);
 }
+
+}  // namespace alembic
+}  // namespace io
+}  // namespace blender
diff --git a/tests/gtests/alembic/abc_matrix_test.cc b/tests/gtests/alembic/abc_matrix_test.cc
index 60dfd4e30cf..fe0635ea7ab 100644
--- a/tests/gtests/alembic/abc_matrix_test.cc
+++ b/tests/gtests/alembic/abc_matrix_test.cc
@@ -8,7 +8,9 @@ extern "C" {
 #include "BLI_utildefines.h"
 }
 
-using namespace blender::io::alembic;
+namespace blender {
+namespace io {
+namespace alembic {
 
 TEST(abc_matrix, CreateRotationMatrixY_YfromZ)
 {
@@ -286,3 +288,7 @@ TEST(abc_matrix, CopyM44AxisSwapWithScale_gimbal_ZfromY)
 
   EXPECT_M4_NEAR(expect, result, 1e-5f);
 }
+
+}  // namespace alembic
+}  // namespace io
+}  // namespace blender
diff --git a/tests/python/alembic_tests.py b/tests/python/alembic_tests.py
index 705bb98a060..5f8113729c3 100644
--- a/tests/python/alembic_tests.py
+++ b/tests/python/alembic_tests.py
@@ -214,7 +214,7 @@ class DupliGroupExportTest(AbstractAlembicTest):
         self.run_blender('dupligroup-scene.blend', script)
 
         # Now check the resulting Alembic file.
-        xform = self.abcprop(abc, '/Real_Cube/Linked_Suzanne/Cylinder/Suzanne/.xform')
+        xform = self.abcprop(abc, '/Real_Cube/Linked_Suzanne/Cylinder-0/Suzanne-1/.xform')
         self.assertEqual(1, xform['.inherits'])
         self.assertAlmostEqualFloatArray(
             xform['.vals'],
@@ -232,7 +232,7 @@ class DupliGroupExportTest(AbstractAlembicTest):
         self.run_blender('dupligroup-scene.blend', script)
 
         # Now check the resulting Alembic file.
-        xform = self.abcprop(abc, '/Suzanne/.xform')
+        xform = self.abcprop(abc, '/Suzanne-1/.xform')
         self.assertEqual(1, xform['.inherits'])
 
         self.assertAlmostEqualFloatArray(