1 files changed, 41 insertions, 0 deletions

diff --git a/source/blender/io/alembic/exporter/abc_writer_abstract.h b/source/blender/io/alembic/exporter/abc_writer_abstract.h
index 59c55330443..d23e69cf73e 100644
--- a/source/blender/io/alembic/exporter/abc_writer_abstract.h
+++ b/source/blender/io/alembic/exporter/abc_writer_abstract.h
@@ -19,6 +19,7 @@
 #pragma once
 
 #include "IO_abstract_hierarchy_iterator.h"
+#include "abc_custom_props.h"
 #include "abc_hierarchy_iterator.h"
 
 #include <Alembic/Abc/OObject.h>
@@ -27,6 +28,7 @@
 #include "DEG_depsgraph_query.h"
 #include "DNA_material_types.h"
 
+struct IDProperty;
 struct Material;
 struct Object;
 
@@ -44,6 +46,9 @@ class ABCAbstractWriter : public AbstractHierarchyWriter {
   /* Visibility of this writer's data in Alembic. */
   Alembic::Abc::OCharProperty abc_visibility_;
 
+  /* Optional writer for custom properties. */
+  std::unique_ptr<CustomPropertiesExporter> custom_props_;
+
  public:
   explicit ABCAbstractWriter(const ABCWriterConstructorArgs &args);
   virtual ~ABCAbstractWriter();
@@ -59,6 +64,7 @@ class ABCAbstractWriter : public AbstractHierarchyWriter {
    * Empty). */
   virtual bool is_supported(const HierarchyContext *context) const;
 
+  uint32_t timesample_index() const;
   const Imath::Box3d &bounding_box() const;
 
   /* Called by AlembicHierarchyCreator after checking that the data is supported via
@@ -67,12 +73,47 @@ class ABCAbstractWriter : public AbstractHierarchyWriter {
 
   virtual Alembic::Abc::OObject get_alembic_object() const = 0;
 
+  /* Return the Alembic object's CompoundProperty that'll contain the custom properties.
+   *
+   * This function is called whenever there are custom properties to be written to Alembic. It
+   * should call abc_schema_prop_for_custom_props() with the writer's Alembic schema object.
+   *
+   * If custom properties are not supported by a specific subclass, it should return an empty
+   * OCompoundProperty() and override ensure_custom_properties_exporter() to do nothing.
+   */
+  virtual Alembic::Abc::OCompoundProperty abc_prop_for_custom_props() = 0;
+
  protected:
   virtual void do_write(HierarchyContext &context) = 0;
 
   virtual void update_bounding_box(Object *object);
 
+  /* Return ID properties of whatever ID datablock is written by this writer. Defaults to the
+   * properties of the object data. Can return nullptr if no custom properties are to be written.
+   */
+  virtual const IDProperty *get_id_properties(const HierarchyContext &context) const;
+
+  virtual void ensure_custom_properties_exporter(const HierarchyContext &context);
+
   void write_visibility(const HierarchyContext &context);
+
+  /* Return the Alembic schema's compound property, which will be used for writing custom
+   * properties.
+   *
+   * This can return either abc_schema.getUserProperties() or abc_schema.getArbGeomParams(). The
+   * former only holds values similar to Blender's custom properties, whereas the latter can also
+   * specify that certain custom properties vary per mesh component (so per face, vertex, etc.). As
+   * such, .userProperties is more suitable for custom properties. However, Maya, Houdini use
+   * .arbGeomParams for custom data.
+   *
+   * Because of this, the code uses this templated function so that there is one place that
+   * determines where custom properties are exporter to.
+   */
+  template<typename T>
+  Alembic::Abc::OCompoundProperty abc_schema_prop_for_custom_props(T abc_schema)
+  {
+    return abc_schema.getUserProperties();
+  }
 };
 
 }  // namespace blender::io::alembic