Fix 2 bugs with scale of position tracks in rest fixer

Both bugs were related to how position animation tracks were adjusted in rest fixer.
First bug: motion scale is applied before subtracting the origin when applying bone roll
Second bug: armature scale was lost when converting basis to quaternion, leading an unscaled position offset to be added to the scaled origin.

editor/import/3d/post_import_plugin_skeleton_rest_fixer.cpp

@@ -436,42 +436,6 @@ void PostImportPluginSkeletonRestFixer::internal_process(InternalImportCategory
 					src_skeleton->set_motion_scale(motion_scale);
 				}
 			}
-
-			TypedArray<Node> nodes = p_base_scene->find_children("*", "AnimationPlayer");
-			while (nodes.size()) {
-				AnimationPlayer *ap = Object::cast_to<AnimationPlayer>(nodes.pop_back());
-				List<StringName> anims;
-				ap->get_animation_list(&anims);
-				for (const StringName &name : anims) {
-					Ref<Animation> anim = ap->get_animation(name);
-					int track_len = anim->get_track_count();
-					for (int i = 0; i < track_len; i++) {
-						if (anim->track_get_path(i).get_subname_count() != 1 || anim->track_get_type(i) != Animation::TYPE_POSITION_3D) {
-							continue;
-						}
-
-						if (anim->track_is_compressed(i)) {
-							continue; // Shouldn't occur in internal_process().
-						}
-
-						String track_path = String(anim->track_get_path(i).get_concatenated_names());
-						Node *node = (ap->get_node(ap->get_root_node()))->get_node(NodePath(track_path));
-						ERR_CONTINUE(!node);
-
-						Skeleton3D *track_skeleton = Object::cast_to<Skeleton3D>(node);
-						if (!track_skeleton || track_skeleton != src_skeleton) {
-							continue;
-						}
-
-						real_t mlt = 1 / src_skeleton->get_motion_scale();
-						int key_len = anim->track_get_key_count(i);
-						for (int j = 0; j < key_len; j++) {
-							Vector3 pos = static_cast<Vector3>(anim->track_get_key_value(i, j));
-							anim->track_set_key_value(i, j, pos * mlt);
-						}
-					}
-				}
-			}
 		}
 
 		// Overwrite axis.
@@ -587,22 +551,24 @@ void PostImportPluginSkeletonRestFixer::internal_process(InternalImportCategory
 									anim->track_set_key_value(i, j, new_pg_q.inverse() * old_pg_q * qt * old_rest_q.inverse() * old_pg_q.inverse() * new_pg_q * new_rest_q);
 								}
 							} else if (anim->track_get_type(i) == Animation::TYPE_SCALE_3D) {
-								Basis old_rest_b = old_rest.basis;
+								Basis old_rest_b_inv = old_rest.basis.inverse();
 								Basis new_rest_b = new_rest.basis;
 								Basis old_pg_b = old_pg.basis;
 								Basis new_pg_b = new_pg.basis;
+								Basis old_pg_b_inv = old_pg.basis.inverse();
+								Basis new_pg_b_inv = new_pg.basis.inverse();
 								for (int j = 0; j < key_len; j++) {
 									Basis sc = Basis().scaled(static_cast<Vector3>(anim->track_get_key_value(i, j)));
-									anim->track_set_key_value(i, j, (new_pg_b.inverse() * old_pg_b * sc * old_rest_b.inverse() * old_pg_b.inverse() * new_pg_b * new_rest_b).get_scale());
+									anim->track_set_key_value(i, j, (new_pg_b_inv * old_pg_b * sc * old_rest_b_inv * old_pg_b_inv * new_pg_b * new_rest_b).get_scale());
 								}
 							} else {
 								Vector3 old_rest_o = old_rest.origin;
 								Vector3 new_rest_o = new_rest.origin;
-								Quaternion old_pg_q = old_pg.basis.get_rotation_quaternion();
-								Quaternion new_pg_q = new_pg.basis.get_rotation_quaternion();
+								Basis old_pg_b = old_pg.basis;
+								Basis new_pg_b = new_pg.basis;
 								for (int j = 0; j < key_len; j++) {
 									Vector3 ps = static_cast<Vector3>(anim->track_get_key_value(i, j));
-									anim->track_set_key_value(i, j, new_pg_q.xform_inv(old_pg_q.xform(ps - old_rest_o)) + new_rest_o);
+									anim->track_set_key_value(i, j, new_pg_b.xform_inv(old_pg_b.xform(ps - old_rest_o)) + new_rest_o);
 								}
 							}
 						}
@@ -637,6 +603,45 @@ void PostImportPluginSkeletonRestFixer::internal_process(InternalImportCategory
 			is_rest_changed = true;
 		}
 
+		// Scale position tracks by motion scale if normalize position tracks.
+		if (bool(p_options["retarget/rest_fixer/normalize_position_tracks"])) {
+			TypedArray<Node> nodes = p_base_scene->find_children("*", "AnimationPlayer");
+			while (nodes.size()) {
+				AnimationPlayer *ap = Object::cast_to<AnimationPlayer>(nodes.pop_back());
+				List<StringName> anims;
+				ap->get_animation_list(&anims);
+				for (const StringName &name : anims) {
+					Ref<Animation> anim = ap->get_animation(name);
+					int track_len = anim->get_track_count();
+					for (int i = 0; i < track_len; i++) {
+						if (anim->track_get_path(i).get_subname_count() != 1 || anim->track_get_type(i) != Animation::TYPE_POSITION_3D) {
+							continue;
+						}
+
+						if (anim->track_is_compressed(i)) {
+							continue; // Shouldn't occur in internal_process().
+						}
+
+						String track_path = String(anim->track_get_path(i).get_concatenated_names());
+						Node *node = (ap->get_node(ap->get_root_node()))->get_node(NodePath(track_path));
+						ERR_CONTINUE(!node);
+
+						Skeleton3D *track_skeleton = Object::cast_to<Skeleton3D>(node);
+						if (!track_skeleton || track_skeleton != src_skeleton) {
+							continue;
+						}
+
+						real_t mlt = 1 / src_skeleton->get_motion_scale();
+						int key_len = anim->track_get_key_count(i);
+						for (int j = 0; j < key_len; j++) {
+							Vector3 pos = static_cast<Vector3>(anim->track_get_key_value(i, j));
+							anim->track_set_key_value(i, j, pos * mlt);
+						}
+					}
+				}
+			}
+		}
+
 		if (is_rest_changed) {
 			// Fix skin.
 			{