Tweak API to support adding evaluated meshes to main database

One of the usecases is to create mesh from an object is a manner similar to
how Apply Modifiers does it, and have it in the bmain so it can be referenced
by other objects.

This usecase is something what went unnoticed in the previous API changes, so
here is a followup.

Summary of changes:

* bpy.meshes.new_from_object() behaves almost the same as before this change.
  The difference now is that it now ensures all referenced data-blocks are
	original (for example, materials referenced by the mesh).

* object.to_mesh() now creates free-standing Mesh data-block which is outside
  of any bmain. The object owns it, which guarantees the memory never leaks.

  It is possible to force free memory by calling object.to_mesh_clear().

Reviewers: brecht

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D4875

1 files changed, 7 insertions, 1 deletions

diff --git a/source/blender/blenkernel/BKE_mesh.h b/source/blender/blenkernel/BKE_mesh.h
index 8ea54457f38..c410946f438 100644
--- a/source/blender/blenkernel/BKE_mesh.h
+++ b/source/blender/blenkernel/BKE_mesh.h
@@ -208,7 +208,13 @@ float (*BKE_mesh_vertexCos_get(const struct Mesh *me, int *r_numVerts))[3];
 
 void BKE_mesh_split_faces(struct Mesh *mesh, bool free_loop_normals);
 
-struct Mesh *BKE_mesh_new_from_object(struct Main *bmain, struct Object *object);
+/* Create new mesh from the given object at its current state.
+ * The owner of this mesh is unknown, it is up to the caller to decide. */
+struct Mesh *BKE_mesh_new_from_object(struct Object *object);
+
+/* This is a version of BKE_mesh_new_from_object() which stores mesh in the given main database. */
+struct Mesh *BKE_mesh_new_from_object_to_bmain(struct Main *bmain, struct Object *object);
+
 struct Mesh *BKE_mesh_create_derived_for_modifier(struct Depsgraph *depsgraph,
                                                   struct Scene *scene,
                                                   struct Object *ob_eval,