Animation: add function to blend Action into pose

Add function `BKE_pose_apply_action_blend()`, which blends a given
Action into current pose. The Action is evaluated at a specified frame,
and the result is applied to the armature's pose.

A blend factor can be given to blend between the current pose and the
one in the Action. Quaternions are interpolated with SLERP; it is
assumed that their FCurves are consecutively stored in the Action.

This function will be used in the upcoming new Pose Library.

1 files changed, 6 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_animsys.h b/source/blender/blenkernel/BKE_animsys.h
index 030560015a9..07da9d75e59 100644
--- a/source/blender/blenkernel/BKE_animsys.h
+++ b/source/blender/blenkernel/BKE_animsys.h
@@ -268,6 +268,12 @@ void animsys_evaluate_action(struct PointerRNA *ptr,
                              const struct AnimationEvalContext *anim_eval_context,
                              bool flush_to_original);
 
+/* Evaluate action, and blend the result into the current values (instead of overwriting fully). */
+void animsys_blend_in_action(struct PointerRNA *ptr,
+                             struct bAction *act,
+                             const AnimationEvalContext *anim_eval_context,
+                             float blend_factor);
+
 /* Evaluate Action Group */
 void animsys_evaluate_action_group(struct PointerRNA *ptr,
                                    struct bAction *act,