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, 133 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/armature_pose.cc b/source/blender/blenkernel/intern/armature_pose.cc
new file mode 100644
index 00000000000..a9613da2335
--- /dev/null
+++ b/source/blender/blenkernel/intern/armature_pose.cc
@@ -0,0 +1,133 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2015 Blender Foundation.
+ * All rights reserved.
+ *
+ * Defines and code for core node types
+ */
+
+/** \file
+ * \ingroup bke
+ */
+
+#include "BKE_animsys.h"
+#include "BKE_armature.h"
+
+#include "BLI_set.hh"
+
+#include "DNA_action_types.h"
+#include "DNA_anim_types.h"
+#include "DNA_armature_types.h"
+#include "DNA_object_types.h"
+
+#include "RNA_access.h"
+
+namespace {
+using BoneNameSet = blender::Set<std::string>;
+
+// Forward declarations.
+BoneNameSet pose_apply_find_selected_bones(const bPose *pose);
+void pose_apply_disable_fcurves_for_unselected_bones(bAction *action,
+                                                     const BoneNameSet &selected_bone_names);
+void pose_apply_restore_fcurves(bAction *action);
+}  // namespace
+
+void BKE_pose_apply_action(struct Object *ob,
+                           struct bAction *action,
+                           struct AnimationEvalContext *anim_eval_context)
+{
+  bPose *pose = ob->pose;
+  if (pose == NULL) {
+    return;
+  }
+
+  const BoneNameSet selected_bone_names = pose_apply_find_selected_bones(pose);
+  const bool limit_to_selected_bones = !selected_bone_names.is_empty();
+
+  if (limit_to_selected_bones) {
+    /* Mute all FCurves that are not associated with selected bones. This separates the concept of
+     * bone selection from the FCurve evaluation code. */
+    pose_apply_disable_fcurves_for_unselected_bones(action, selected_bone_names);
+  }
+
+  /* Apply the Action. */
+  PointerRNA pose_owner_ptr;
+  RNA_id_pointer_create(&ob->id, &pose_owner_ptr);
+  animsys_evaluate_action(&pose_owner_ptr, action, anim_eval_context, false);
+
+  if (limit_to_selected_bones) {
+    pose_apply_restore_fcurves(action);
+  }
+}
+
+namespace {
+BoneNameSet pose_apply_find_selected_bones(const bPose *pose)
+{
+  BoneNameSet selected_bone_names;
+  bool all_bones_selected = true;
+  bool no_bones_selected = true;
+
+  LISTBASE_FOREACH (bPoseChannel *, pchan, &pose->chanbase) {
+    const bool is_selected = (pchan->bone->flag & BONE_SELECTED) != 0 &&
+                             (pchan->bone->flag & BONE_HIDDEN_P) == 0;
+    all_bones_selected &= is_selected;
+    no_bones_selected &= !is_selected;
+
+    if (is_selected) {
+      /* Bone names are unique, so no need to check for duplicates. */
+      selected_bone_names.add_new(pchan->name);
+    }
+  }
+
+  /* If no bones are selected, act as if all are. */
+  if (all_bones_selected || no_bones_selected) {
+    return BoneNameSet(); /* An empty set means "ignore bone selection". */
+  }
+  return selected_bone_names;
+}
+
+void pose_apply_restore_fcurves(bAction *action)
+{
+  /* TODO(Sybren): Restore the FCurve flags, instead of just erasing the 'disabled' flag. */
+  LISTBASE_FOREACH (FCurve *, fcu, &action->curves) {
+    fcu->flag &= ~FCURVE_DISABLED;
+  }
+}
+
+void pose_apply_disable_fcurves_for_unselected_bones(bAction *action,
+                                                     const BoneNameSet &selected_bone_names)
+{
+  LISTBASE_FOREACH (FCurve *, fcu, &action->curves) {
+    if (!fcu->rna_path || !strstr(fcu->rna_path, "pose.bones[")) {
+      continue;
+    }
+
+    /* Get bone name, and check if this bone is selected. */
+    char *bone_name = BLI_str_quoted_substrN(fcu->rna_path, "pose.bones[");
+    if (!bone_name) {
+      continue;
+    }
+    const bool is_selected = selected_bone_names.contains(bone_name);
+    MEM_freeN(bone_name);
+    if (is_selected) {
+      continue;
+    }
+
+    fcu->flag |= FCURVE_DISABLED;
+  }
+}
+
+}  // namespace