Alembic: exporting MetaBalls as mesh

- Only basis balls are exported, as they represent the resulting mesh.
  As a result the mesh is written to Alembic using the name of the basis
  ball.
- MetaBalls are converted to a mesh on every frame, then an
  AbcMeshWriter is used to write that mesh to Alembic.

source/blender/alembic/CMakeLists.txt

@@ -33,6 +33,7 @@ set(INC
 	../makesdna
 	../makesrna
 	../windowmanager
+	../depsgraph
 	../../../intern/guardedalloc
 	../../../intern/utfconv
 )
@@ -51,6 +52,7 @@ set(SRC
 	intern/abc_curves.cc
 	intern/abc_exporter.cc
 	intern/abc_hair.cc
+	intern/abc_mball.cc
 	intern/abc_mesh.cc
 	intern/abc_nurbs.cc
 	intern/abc_object.cc
@@ -66,6 +68,7 @@ set(SRC
 	intern/abc_curves.h
 	intern/abc_exporter.h
 	intern/abc_hair.h
+	intern/abc_mball.h
 	intern/abc_mesh.h
 	intern/abc_nurbs.h
 	intern/abc_object.h

source/blender/alembic/intern/abc_exporter.cc

@@ -28,6 +28,7 @@
 #include "abc_camera.h"
 #include "abc_curves.h"
 #include "abc_hair.h"
+#include "abc_mball.h"
 #include "abc_mesh.h"
 #include "abc_nurbs.h"
 #include "abc_points.h"
@@ -37,6 +38,7 @@
 extern "C" {
 #include "DNA_camera_types.h"
 #include "DNA_curve_types.h"
+#include "DNA_meta_types.h"
 #include "DNA_mesh_types.h"
 #include "DNA_modifier_types.h"
 #include "DNA_object_types.h"
@@ -54,6 +56,7 @@ extern "C" {
 #include "BKE_global.h"
 #include "BKE_idprop.h"
 #include "BKE_main.h"
+#include "BKE_mball.h"
 #include "BKE_modifier.h"
 #include "BKE_particle.h"
 #include "BKE_scene.h"
@@ -108,7 +111,7 @@ static bool object_is_smoke_sim(Object *ob)
 	return false;
 }
 
-static bool object_type_is_exportable(Object *ob)
+static bool object_type_is_exportable(Scene *scene, Object *ob)
 {
 	switch (ob->type) {
 		case OB_MESH:
@@ -122,6 +125,8 @@ static bool object_type_is_exportable(Object *ob)
 		case OB_SURF:
 		case OB_CAMERA:
 			return true;
+		case OB_MBALL:
+			return AbcMBallWriter::isBasisBall(scene, ob);
 		default:
 			return false;
 	}
@@ -163,8 +168,9 @@ static bool export_object(const ExportSettings * const settings, Object *ob,
 
 /* ************************************************************************** */
 
-AbcExporter::AbcExporter(Scene *scene, const char *filename, ExportSettings &settings)
-    : m_settings(settings)
+AbcExporter::AbcExporter(Main *bmain, Scene *scene, const char *filename, ExportSettings &settings)
+    : m_bmain(bmain)
+    , m_settings(settings)
     , m_filename(filename)
     , m_trans_sampling_index(0)
     , m_shape_sampling_index(0)
@@ -361,11 +367,9 @@ void AbcExporter::createTransformWritersHierarchy(EvaluationContext *eval_ctx)
 		switch (ob->type) {
 			case OB_LAMP:
 			case OB_LATTICE:
-			case OB_MBALL:
 			case OB_SPEAKER:
 				/* We do not export transforms for objects of these classes. */
 				break;
-
 			default:
 				exploreTransform(eval_ctx, ob, ob->parent);
 		}
@@ -382,7 +386,7 @@ void AbcExporter::exploreTransform(EvaluationContext *eval_ctx, Object *ob, Obje
 		return;
 	}
 
-	if (object_type_is_exportable(ob)) {
+	if (object_type_is_exportable(m_scene, ob)) {
 		createTransformWriter(ob, parent, dupliObParent);
 	}
 
@@ -547,7 +551,7 @@ void AbcExporter::createParticleSystemsWriters(Object *ob, AbcTransformWriter *x
 
 void AbcExporter::createShapeWriter(Object *ob, Object *dupliObParent)
 {
-	if (!object_type_is_exportable(ob)) {
+	if (!object_type_is_exportable(m_scene, ob)) {
 		return;
 	}
 
@@ -613,6 +617,18 @@ void AbcExporter::createShapeWriter(Object *ob, Object *dupliObParent)
 
 			break;
 		}
+		case OB_MBALL:
+		{
+			MetaBall *mball = static_cast<MetaBall *>(ob->data);
+			if (!mball) {
+				return;
+			}
+
+			m_shapes.push_back(new AbcMBallWriter(
+			                       m_bmain, m_scene, ob, xform,
+			                       m_shape_sampling_index, m_settings));
+			break;
+		}
 	}
 }
 

source/blender/alembic/intern/abc_exporter.h

@@ -81,6 +81,7 @@ struct ExportSettings {
 };
 
 class AbcExporter {
+	Main *m_bmain;
 	ExportSettings &m_settings;
 
 	const char *m_filename;
@@ -98,7 +99,7 @@ class AbcExporter {
 	std::vector<AbcObjectWriter *> m_shapes;
 
 public:
-	AbcExporter(Scene *scene, const char *filename, ExportSettings &settings);
+	AbcExporter(Main *bmain, Scene *scene, const char *filename, ExportSettings &settings);
 	~AbcExporter();
 
 	void operator()(Main *bmain, float &progress, bool &was_canceled);

source/blender/alembic/intern/abc_mball.cc

@@ -0,0 +1,122 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * 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.
+ *
+ * Contributor(s): Sybren A. Stüvel
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+#include "abc_mball.h"
+#include "abc_mesh.h"
+#include "abc_transform.h"
+
+extern "C" {
+#include "DNA_meta_types.h"
+#include "DNA_mesh_types.h"
+#include "DNA_object_types.h"
+
+#include "BKE_curve.h"
+#include "BKE_depsgraph.h"
+#include "BKE_displist.h"
+#include "BKE_main.h"
+#include "BKE_mball.h"
+#include "BKE_mesh.h"
+#include "BKE_object.h"
+
+#include "DEG_depsgraph.h"
+#include "MEM_guardedalloc.h"
+}
+
+AbcMBallWriter::AbcMBallWriter(
+        Main *bmain,
+        Scene *scene,
+        Object *ob,
+        AbcTransformWriter *parent,
+        uint32_t time_sampling,
+        ExportSettings &settings)
+    : AbcObjectWriter(scene, ob, time_sampling, settings, parent)
+    , m_bmain(bmain)
+{
+	m_is_animated = isAnimated();
+
+	m_mesh_ob = BKE_object_copy(bmain, ob);
+	m_mesh_ob->curve_cache = (CurveCache*)MEM_callocN(
+	                             sizeof(CurveCache),
+	                             "CurveCache for AbcMBallWriter");
+
+	m_mesh_writer = new AbcMeshWriter(scene, m_mesh_ob, parent,
+	                                  time_sampling, settings);
+	m_mesh_writer->setIsAnimated(m_is_animated);
+}
+
+
+AbcMBallWriter::~AbcMBallWriter()
+{
+	delete m_mesh_writer;
+	BKE_object_free(m_mesh_ob);
+}
+
+bool AbcMBallWriter::isAnimated() const
+{
+	MetaBall *mb = static_cast<MetaBall *>(m_object->data);
+	if (mb->adt != NULL) return true;
+
+	/* Any movement of any object in the parent chain
+	 * could cause the mball to deform. */
+	for (Object *ob = m_object; ob != NULL; ob = ob->parent) {
+		if (ob->adt != NULL) return true;
+	}
+	return false;
+}
+
+void AbcMBallWriter::do_write()
+{
+	/* We have already stored a sample for this object. */
+	if (!m_first_frame && !m_is_animated)
+		return;
+
+	Mesh *tmpmesh = BKE_mesh_add(m_bmain, ((ID *)m_object->data)->name + 2);
+	BLI_assert(tmpmesh != NULL);
+	m_mesh_ob->data = tmpmesh;
+
+	/* BKE_mesh_add gives us a user count we don't need */
+	id_us_min(&tmpmesh->id);
+
+	ListBase disp = {NULL, NULL};
+	/* TODO(sergey): This is gonna to work for until EvaluationContext
+	 *               only contains for_render flag. As soon as CoW is
+	 *               implemented, this is to be rethinked.
+	 */
+	EvaluationContext eval_ctx;
+	DEG_evaluation_context_init(&eval_ctx, DAG_EVAL_RENDER);
+	BKE_displist_make_mball_forRender(&eval_ctx, m_scene, m_object, &disp);
+	BKE_mesh_from_metaball(&disp, tmpmesh);
+	BKE_displist_free(&disp);
+
+	BKE_mesh_texspace_copy_from_object(tmpmesh, m_mesh_ob);
+
+	m_mesh_writer->write();
+
+	BKE_id_free(m_bmain, tmpmesh);
+	m_mesh_ob->data = NULL;
+}
+
+bool AbcMBallWriter::isBasisBall(Scene *scene, Object *ob)
+{
+	Object *basis_ob = BKE_mball_basis_find(scene, ob);
+	return ob == basis_ob;
+}

source/blender/alembic/intern/abc_mball.h

@@ -0,0 +1,61 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * 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.
+ *
+ * Contributor(s): Sybren A. Stüvel
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+#ifndef __ABC_MBALL_H__
+#define __ABC_MBALL_H__
+
+#include "abc_object.h"
+
+struct AbcMeshWriter;
+struct Main;
+struct MetaBall;
+struct Object;
+
+/* AbcMBallWriter converts the metaballs to meshes at every frame,
+ * and defers to a wrapped AbcMeshWriter to perform the writing
+ * to the Alembic file. Only the basis balls are exported, as this
+ * results in the entire shape as one mesh. */
+class AbcMBallWriter : public AbcObjectWriter {
+	AbcMeshWriter *m_mesh_writer;
+	Object *m_mesh_ob;
+	bool m_is_animated;
+	Main *m_bmain;
+public:
+	AbcMBallWriter(
+	        Main *bmain,
+	        Scene *scene,
+	        Object *ob,
+	        AbcTransformWriter *parent,
+	        uint32_t time_sampling,
+	        ExportSettings &settings);
+
+	~AbcMBallWriter();
+
+	static bool isBasisBall(Scene *scene, Object *ob);
+
+private:
+	virtual void do_write();
+	bool isAnimated() const;
+};
+
+
+#endif  /* __ABC_MBALL_H__ */

source/blender/alembic/intern/abc_mesh.cc

@@ -358,6 +358,11 @@ bool AbcMeshWriter::isAnimated() const
 	return me->adt != NULL;
 }
 
+void AbcMeshWriter::setIsAnimated(bool is_animated)
+{
+	m_is_animated = is_animated;
+}
+
 void AbcMeshWriter::do_write()
 {
 	/* We have already stored a sample for this object. */

source/blender/alembic/intern/abc_mesh.h

@@ -57,6 +57,7 @@ public:
 	              ExportSettings &settings);
 
 	~AbcMeshWriter();
+	void setIsAnimated(bool is_animated);
 
 private:
 	virtual void do_write();

source/blender/alembic/intern/alembic_capi.cc

@@ -259,7 +259,7 @@ static void export_startjob(void *customdata, short *stop, short *do_update, flo
 
 	try {
 		Scene *scene = data->scene;
-		AbcExporter exporter(scene, data->filename, data->settings);
+		AbcExporter exporter(data->bmain, scene, data->filename, data->settings);
 
 		const int orig_frame = CFRA;
 

tests/gtests/alembic/CMakeLists.txt

@@ -25,6 +25,7 @@ set(INC
 	.
 	..
 	../../../source/blender/blenlib
+	../../../source/blender/blenkernel
 	../../../source/blender/alembic
 	../../../source/blender/makesdna
 	${ALEMBIC_INCLUDE_DIRS}

tests/gtests/alembic/abc_export_test.cc

@@ -5,6 +5,7 @@
 #include "intern/abc_exporter.h"
 
 extern "C" {
+#include "BKE_global.h"
 #include "BLI_utildefines.h"
 #include "BLI_math.h"
 #include "DNA_scene_types.h"
@@ -12,8 +13,8 @@ extern "C" {
 
 class TestableAbcExporter : public AbcExporter {
 public:
-	TestableAbcExporter(Scene *scene, const char *filename, ExportSettings &settings)
-	    : AbcExporter(scene, filename, settings)
+	TestableAbcExporter(Main *bmain, Scene *scene, const char *filename, ExportSettings &settings)
+	    : AbcExporter(bmain, scene, filename, settings)
 	{}
 
 	void getShutterSamples(unsigned int nr_of_samples,
@@ -57,7 +58,7 @@ protected:
 	// Call after setting up the settings.
 	void createExporter()
 	{
-		exporter = new TestableAbcExporter(&scene, "somefile.abc", settings);
+		exporter = new TestableAbcExporter(G.main, &scene, "somefile.abc", settings);
 	}
 };