Alembic: use object-oriented approach in ABC_read_mesh()

This is easier to extend than the if/else if/else chain that was in place,
and allows for somewhat more granular error messages.

12 files changed, 128 insertions, 37 deletions

diff --git a/source/blender/alembic/intern/abc_camera.cc b/source/blender/alembic/intern/abc_camera.cc
index 33344f6c9c5..16416205983 100644
--- a/source/blender/alembic/intern/abc_camera.cc
+++ b/source/blender/alembic/intern/abc_camera.cc
@@ -117,6 +117,23 @@ bool AbcCameraReader::valid() const
 	return m_schema.valid();
 }
 
+bool AbcCameraReader::accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+                                          const Object *const ob,
+                                          const char **err_str) const
+{
+	if (!Alembic::AbcGeom::ICamera::matches(alembic_header)) {
+		*err_str = "Object type mismatch, Alembic object path pointed to Camera when importing, but not any more.";
+		return false;
+	}
+
+	if (ob->type != OB_CAMERA) {
+		*err_str = "Object type mismatch, Alembic object path points to Camera.";
+		return false;
+	}
+
+	return true;
+}
+
 void AbcCameraReader::readObjectData(Main *bmain, const ISampleSelector &sample_sel)
 {
 	Camera *bcam = static_cast<Camera *>(BKE_camera_add(bmain, m_data_name.c_str()));
diff --git a/source/blender/alembic/intern/abc_camera.h b/source/blender/alembic/intern/abc_camera.h
index 0201dd9d6e1..16c5cccd5ea 100644
--- a/source/blender/alembic/intern/abc_camera.h
+++ b/source/blender/alembic/intern/abc_camera.h
@@ -54,6 +54,9 @@ public:
 	AbcCameraReader(const Alembic::Abc::IObject &object, ImportSettings &settings);
 
 	bool valid() const;
+	bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+	                         const Object *const ob,
+	                         const char **err_str) const;
 
 	void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel);
 };
diff --git a/source/blender/alembic/intern/abc_curves.cc b/source/blender/alembic/intern/abc_curves.cc
index d85d8df4d77..67b2cb8ae8c 100644
--- a/source/blender/alembic/intern/abc_curves.cc
+++ b/source/blender/alembic/intern/abc_curves.cc
@@ -211,6 +211,23 @@ bool AbcCurveReader::valid() const
 	return m_curves_schema.valid();
 }
 
+bool AbcCurveReader::accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+                                         const Object *const ob,
+                                         const char **err_str) const
+{
+	if (!Alembic::AbcGeom::ICurves::matches(alembic_header)) {
+		*err_str = "Object type mismatch, Alembic object path pointed to Curves when importing, but not any more.";
+		return false;
+	}
+
+	if (ob->type != OB_EMPTY) {
+		*err_str = "Object type mismatch, Alembic object path points to Curves.";
+		return false;
+	}
+
+	return true;
+}
+
 void AbcCurveReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel)
 {
 	Curve *cu = BKE_curve_add(bmain, m_data_name.c_str(), OB_CURVE);
diff --git a/source/blender/alembic/intern/abc_curves.h b/source/blender/alembic/intern/abc_curves.h
index 1ad6d0bf278..a9231f947b2 100644
--- a/source/blender/alembic/intern/abc_curves.h
+++ b/source/blender/alembic/intern/abc_curves.h
@@ -54,6 +54,9 @@ public:
 	AbcCurveReader(const Alembic::Abc::IObject &object, ImportSettings &settings);
 
 	bool valid() const;
+	bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+	                         const Object *const ob,
+	                         const char **err_str) const;
 
 	void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel);
 	DerivedMesh *read_derivedmesh(DerivedMesh *dm,
diff --git a/source/blender/alembic/intern/abc_mesh.cc b/source/blender/alembic/intern/abc_mesh.cc
index 39186ec55dc..32795e70e92 100644
--- a/source/blender/alembic/intern/abc_mesh.cc
+++ b/source/blender/alembic/intern/abc_mesh.cc
@@ -1048,6 +1048,23 @@ void AbcMeshReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelec
 	}
 }
 
+bool AbcMeshReader::accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+                                        const Object *const ob,
+                                        const char **err_str) const
+{
+	if (!Alembic::AbcGeom::IPolyMesh::matches(alembic_header)) {
+		*err_str = "Object type mismatch, Alembic object path pointed to PolyMesh when importing, but not any more.";
+		return false;
+	}
+
+	if (ob->type != OB_MESH) {
+		*err_str = "Object type mismatch, Alembic object path points to PolyMesh.";
+		return false;
+	}
+
+	return true;
+}
+
 DerivedMesh *AbcMeshReader::read_derivedmesh(DerivedMesh *dm,
                                              const ISampleSelector &sample_sel,
                                              int read_flag,
@@ -1239,6 +1256,23 @@ bool AbcSubDReader::valid() const
 	return m_schema.valid();
 }
 
+bool AbcSubDReader::accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+                                        const Object *const ob,
+                                        const char **err_str) const
+{
+	if (!Alembic::AbcGeom::ISubD::matches(alembic_header)) {
+		*err_str = "Object type mismatch, Alembic object path pointed to SubD when importing, but not any more.";
+		return false;
+	}
+
+	if (ob->type != OB_MESH) {
+		*err_str = "Object type mismatch, Alembic object path points to SubD.";
+		return false;
+	}
+
+	return true;
+}
+
 void AbcSubDReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel)
 {
 	Mesh *mesh = BKE_mesh_add(bmain, m_data_name.c_str());
diff --git a/source/blender/alembic/intern/abc_mesh.h b/source/blender/alembic/intern/abc_mesh.h
index 1b67c80cc72..6bf1dde3d1d 100644
--- a/source/blender/alembic/intern/abc_mesh.h
+++ b/source/blender/alembic/intern/abc_mesh.h
@@ -99,7 +99,9 @@ public:
 	AbcMeshReader(const Alembic::Abc::IObject &object, ImportSettings &settings);
 
 	bool valid() const;
-
+	bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+	                       const Object *const ob,
+	                       const char **err_str) const;
 	void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel);
 
 	DerivedMesh *read_derivedmesh(DerivedMesh *dm,
@@ -123,7 +125,9 @@ public:
 	AbcSubDReader(const Alembic::Abc::IObject &object, ImportSettings &settings);
 
 	bool valid() const;
-
+	bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+	                         const Object *const ob,
+	                         const char **err_str) const;
 	void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel);
 	DerivedMesh *read_derivedmesh(DerivedMesh *dm,
 	                              const Alembic::Abc::ISampleSelector &sample_sel,
diff --git a/source/blender/alembic/intern/abc_object.h b/source/blender/alembic/intern/abc_object.h
index c5da84d3c2a..1462f93a422 100644
--- a/source/blender/alembic/intern/abc_object.h
+++ b/source/blender/alembic/intern/abc_object.h
@@ -169,6 +169,9 @@ public:
 	const std::string & data_name() const { return m_data_name; }
 
 	virtual bool valid() const = 0;
+	virtual bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+	                                 const Object *const ob,
+	                                 const char **err_str) const = 0;
 
 	virtual void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel) = 0;
 
diff --git a/source/blender/alembic/intern/abc_points.cc b/source/blender/alembic/intern/abc_points.cc
index d5ecf16b793..3a2ca8a1b47 100644
--- a/source/blender/alembic/intern/abc_points.cc
+++ b/source/blender/alembic/intern/abc_points.cc
@@ -151,6 +151,23 @@ bool AbcPointsReader::valid() const
 	return m_schema.valid();
 }
 
+bool AbcPointsReader::accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+                                          const Object *const ob,
+                                          const char **err_str) const
+{
+	if (!Alembic::AbcGeom::IPoints::matches(alembic_header)) {
+		*err_str = "Object type mismatch, Alembic object path pointed to Points when importing, but not any more.";
+		return false;
+	}
+
+	if (ob->type != OB_EMPTY) {
+		*err_str = "Object type mismatch, Alembic object path points to Points.";
+		return false;
+	}
+
+	return true;
+}
+
 void AbcPointsReader::readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel)
 {
 	Mesh *mesh = BKE_mesh_add(bmain, m_data_name.c_str());
diff --git a/source/blender/alembic/intern/abc_points.h b/source/blender/alembic/intern/abc_points.h
index 1f74351d302..369a802d763 100644
--- a/source/blender/alembic/intern/abc_points.h
+++ b/source/blender/alembic/intern/abc_points.h
@@ -58,6 +58,9 @@ public:
 	AbcPointsReader(const Alembic::Abc::IObject &object, ImportSettings &settings);
 
 	bool valid() const;
+	bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+	                         const Object *const ob,
+	                         const char **err_str) const;
 
 	void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel);
 
diff --git a/source/blender/alembic/intern/abc_transform.cc b/source/blender/alembic/intern/abc_transform.cc
index c48be361877..e2369e80618 100644
--- a/source/blender/alembic/intern/abc_transform.cc
+++ b/source/blender/alembic/intern/abc_transform.cc
@@ -154,6 +154,23 @@ bool AbcEmptyReader::valid() const
 	return m_schema.valid();
 }
 
+bool AbcEmptyReader::accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+                                         const Object *const ob,
+                                         const char **err_str) const
+{
+	if (!Alembic::AbcGeom::IXform::matches(alembic_header)) {
+		*err_str = "Object type mismatch, Alembic object path pointed to XForm when importing, but not any more.";
+		return false;
+	}
+
+	if (ob->type != OB_EMPTY) {
+		*err_str = "Object type mismatch, Alembic object path points to XForm.";
+		return false;
+	}
+
+	return true;
+}
+
 void AbcEmptyReader::readObjectData(Main *bmain, const ISampleSelector &UNUSED(sample_sel))
 {
 	m_object = BKE_object_add_only_object(bmain, OB_EMPTY,
diff --git a/source/blender/alembic/intern/abc_transform.h b/source/blender/alembic/intern/abc_transform.h
index f2e2edf8010..753a4247e9f 100644
--- a/source/blender/alembic/intern/abc_transform.h
+++ b/source/blender/alembic/intern/abc_transform.h
@@ -68,6 +68,9 @@ public:
 	AbcEmptyReader(const Alembic::Abc::IObject &object, ImportSettings &settings);
 
 	bool valid() const;
+	bool accepts_object_type(const Alembic::AbcCoreAbstract::ObjectHeader &alembic_header,
+	                         const Object *const ob,
+	                         const char **err_str) const;
 
 	void readObjectData(Main *bmain, const Alembic::Abc::ISampleSelector &sample_sel);
 };
diff --git a/source/blender/alembic/intern/alembic_capi.cc b/source/blender/alembic/intern/alembic_capi.cc
index 74b472fdb4e..52864799133 100644
--- a/source/blender/alembic/intern/alembic_capi.cc
+++ b/source/blender/alembic/intern/alembic_capi.cc
@@ -939,43 +939,13 @@ DerivedMesh *ABC_read_mesh(CacheReader *reader,
 	}
 
 	const ObjectHeader &header = iobject.getHeader();
-	ISampleSelector sample_sel(time);
-
-	if (IPolyMesh::matches(header)) {
-		if (ob->type != OB_MESH) {
-			*err_str = "Object type mismatch: object path points to a mesh!";
-			return NULL;
-		}
-
-		return abc_reader->read_derivedmesh(dm, sample_sel, read_flag, err_str);
-	}
-	else if (ISubD::matches(header)) {
-		if (ob->type != OB_MESH) {
-			*err_str = "Object type mismatch: object path points to a subdivision mesh!";
-			return NULL;
-		}
-
-		return abc_reader->read_derivedmesh(dm, sample_sel, read_flag, err_str);
-	}
-	else if (IPoints::matches(header)) {
-		if (ob->type != OB_MESH) {
-			*err_str = "Object type mismatch: object path points to a point cloud (requires a mesh object)!";
-			return NULL;
-		}
-
-		return abc_reader->read_derivedmesh(dm, sample_sel, read_flag, err_str);
-	}
-	else if (ICurves::matches(header)) {
-		if (ob->type != OB_CURVE) {
-			*err_str = "Object type mismatch: object path points to a curve!";
-			return NULL;
-		}
-
-		return abc_reader->read_derivedmesh(dm, sample_sel, read_flag, err_str);
+	if (!abc_reader->accepts_object_type(header, ob, err_str)) {
+		/* err_str is set by acceptsObjectType() */
+		return NULL;
 	}
 
-	*err_str = "Unsupported object type: verify object path"; // or poke developer
-	return NULL;
+	ISampleSelector sample_sel(time);
+	return abc_reader->read_derivedmesh(dm, sample_sel, read_flag, err_str);
 }
 
 /* ************************************************************************** */