Fix T91169: bpy_extras.io_utils.create_derived_objects -> duplis error

This function now takes a depsgraph and a list of objects to avoid
inefficient O(n^2) iteration when extracting instances from all objects
in the scene. Returning an object -> instance map.

Note that keeping compatibility with the existing API wasn't practical
in this case since instances can no longer be generated from the scene
and it's objects.

1 files changed, 34 insertions, 16 deletions

diff --git a/release/scripts/modules/bpy_extras/io_utils.py b/release/scripts/modules/bpy_extras/io_utils.py
index 9e3c5bb64e0..a3b39853b3a 100644
--- a/release/scripts/modules/bpy_extras/io_utils.py
+++ b/release/scripts/modules/bpy_extras/io_utils.py
@@ -25,7 +25,6 @@ __all__ = (
     "axis_conversion",
     "axis_conversion_ensure",
     "create_derived_objects",
-    "free_derived_objects",
     "unpack_list",
     "unpack_face_list",
     "path_reference",
@@ -348,21 +347,40 @@ def axis_conversion_ensure(operator, forward_attr, up_attr):
         return False
 
 
-# return a tuple (free, object list), free is True if memory should be freed
-# later with free_derived_objects()
-def create_derived_objects(scene, ob):
-    if ob.parent and ob.parent.instance_type in {'VERTS', 'FACES'}:
-        return False, None
-
-    if ob.instance_type != 'NONE':
-        ob.dupli_list_create(scene)
-        return True, [(dob.object, dob.matrix) for dob in ob.dupli_list]
-    else:
-        return False, [(ob, ob.matrix_world)]
-
-
-def free_derived_objects(ob):
-    ob.dupli_list_clear()
+def create_derived_objects(depsgraph, objects):
+    """
+    This function takes a sequence of objects, returning their instances.
+
+    :arg depsgraph: The evaluated depsgraph.
+    :type depsgraph: :class:`bpy.types.Depsgraph`
+    :arg objects: A sequencer of objects.
+    :type objects: sequence of :class:`bpy.types.Object`
+    :return: A dictionary where each key is an object from `objects`,
+       values are lists of (:class:`bpy.types.Object`, :class:`mathutils.Matrix`) tuples representing instances.
+    :rtype: dict
+    """
+    result = {}
+    has_instancer = False
+    for ob in objects:
+        ob_parent = ob.parent
+        if ob_parent and ob_parent.instance_type in {'VERTS', 'FACES'}:
+            continue
+        result[ob] = [] if ob.is_instancer else [(ob, ob.matrix_world.copy())]
+
+    if result:
+        for dup in depsgraph.object_instances:
+            dup_parent = dup.parent
+            if dup_parent is None:
+                continue
+            dup_parent_original = dup_parent.original
+            if not dup_parent_original.is_instancer:
+                # The instance has already been added (on assignment).
+                continue
+            instance_list = result.get(dup_parent_original)
+            if instance_list is None:
+                continue
+            instance_list.append((dup.instance_object.original, dup.matrix_world.copy()))
+    return result
 
 
 def unpack_list(list_of_tuples):