Animation: add function to apply a pose from an Action

Add `BKE_pose_apply_action(object, action, anim_eval_context)` function
and expose in RNA as `Pose.apply_action(action, evaluation_time)`.

This makes it possible to do the following:

- Have a rig in pose mode.
- Select a subset of the bones.
- Have some Action loaded that contains the pose you want to apply.
- Run `C.object.pose.apply_pose_from_action(D.actions['PoseName'])`
- The selected bones are now posed as determined by the Action.

Just like Blender's current pose library, having no bones selected acts
the same as having all bones selected.

Manifest Task: T86159

Reviewed By: Severin

Differential Revision: https://developer.blender.org/D10578

1 files changed, 47 insertions, 5 deletions

diff --git a/source/blender/makesrna/intern/rna_pose_api.c b/source/blender/makesrna/intern/rna_pose_api.c
index 59704b00391..d93972aa0ad 100644
--- a/source/blender/makesrna/intern/rna_pose_api.c
+++ b/source/blender/makesrna/intern/rna_pose_api.c
@@ -38,9 +38,14 @@
 
 #ifdef RNA_RUNTIME
 
-/* #include "DNA_anim_types.h" */
+#  include "BKE_animsys.h"
 #  include "BKE_armature.h"
-#  include "DNA_action_types.h" /* bPose */
+#  include "BKE_context.h"
+
+#  include "DNA_action_types.h"
+#  include "DNA_anim_types.h"
+
+#  include "BLI_ghash.h"
 
 static float rna_PoseBone_do_envelope(bPoseChannel *chan, float *vec)
 {
@@ -102,12 +107,49 @@ static void rna_PoseBone_compute_bbone_handles(bPoseChannel *pchan,
   BKE_pchan_bbone_handles_compute(
       &params, ret_h1, ret_roll1, ret_h2, ret_roll2, ease || offsets, offsets);
 }
+
+static void rna_Pose_apply_pose_from_action(ID *pose_owner,
+                                            bContext *C,
+                                            bAction *action,
+                                            const float evaluation_time)
+{
+  BLI_assert(GS(pose_owner->name) == ID_OB);
+  Object *pose_owner_ob = (Object *)pose_owner;
+
+  AnimationEvalContext anim_eval_context = {CTX_data_depsgraph_pointer(C), evaluation_time};
+  BKE_pose_apply_action(pose_owner_ob, action, &anim_eval_context);
+
+  /* Do NOT tag with ID_RECALC_ANIMATION, as that would overwrite the just-applied pose. */
+  DEG_id_tag_update(pose_owner, ID_RECALC_GEOMETRY);
+  WM_event_add_notifier(C, NC_OBJECT | ND_POSE, pose_owner);
+}
+
 #else
 
-void RNA_api_pose(StructRNA *UNUSED(srna))
+void RNA_api_pose(StructRNA *srna)
 {
-  /* FunctionRNA *func; */
-  /* PropertyRNA *parm; */
+  FunctionRNA *func;
+  PropertyRNA *parm;
+
+  func = RNA_def_function(srna, "apply_pose_from_action", "rna_Pose_apply_pose_from_action");
+  RNA_def_function_flag(func, FUNC_USE_SELF_ID | FUNC_NO_SELF | FUNC_USE_CONTEXT);
+  RNA_def_function_ui_description(
+      func,
+      "Apply the given action to this pose by evaluating it at a specific time. Only updates the "
+      "pose of selected bones, or all bones if none are selected");
+
+  parm = RNA_def_pointer(func, "action", "Action", "Action", "The Action containing the pose");
+  RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
+
+  parm = RNA_def_float(func,
+                       "evaluation_time",
+                       0.0f,
+                       -FLT_MAX,
+                       FLT_MAX,
+                       "Evaluation Time",
+                       "Time at which the given action is evaluated to obtain the pose",
+                       -FLT_MAX,
+                       FLT_MAX);
 }
 
 void RNA_api_pose_channel(StructRNA *srna)