Tracking: Implement tracks average operator

Average selected tracks into the new one. This can be used to improve
stability of tracking on blurry or non-very-sharp feature shapes.

Averaging happens for all position, pattern corners and search area.
Disabled markers do not take effect on averaging. Keyframed flag is
copied from source.

Gaps in the source tracks will be linearly interpolated, to reduce
result track jump. Note that this only applies to gaps "inbetween".
This means that if an input track doesn't have markers in the
beginning/end of it, there is nothing to interpolate with and the
result track will jump.

Available from the Track panel, under the Merge category.

Differential Revision: https://developer.blender.org/D6323

3 files changed, 93 insertions, 0 deletions

diff --git a/source/blender/editors/space_clip/clip_intern.h b/source/blender/editors/space_clip/clip_intern.h
index 4848ec72f79..81df8cc8ecd 100644
--- a/source/blender/editors/space_clip/clip_intern.h
+++ b/source/blender/editors/space_clip/clip_intern.h
@@ -191,6 +191,7 @@ void CLIP_OT_clear_solution(struct wmOperatorType *ot);
 
 void CLIP_OT_clear_track_path(struct wmOperatorType *ot);
 void CLIP_OT_join_tracks(struct wmOperatorType *ot);
+void CLIP_OT_average_tracks(struct wmOperatorType *ot);
 
 void CLIP_OT_disable_markers(struct wmOperatorType *ot);
 void CLIP_OT_hide_tracks(struct wmOperatorType *ot);
diff --git a/source/blender/editors/space_clip/space_clip.c b/source/blender/editors/space_clip/space_clip.c
index 33c4bf7c255..085dbccabb2 100644
--- a/source/blender/editors/space_clip/space_clip.c
+++ b/source/blender/editors/space_clip/space_clip.c
@@ -514,6 +514,7 @@ static void clip_operatortypes(void)
   /* clean-up */
   WM_operatortype_append(CLIP_OT_clear_track_path);
   WM_operatortype_append(CLIP_OT_join_tracks);
+  WM_operatortype_append(CLIP_OT_average_tracks);
   WM_operatortype_append(CLIP_OT_track_copy_color);
 
   WM_operatortype_append(CLIP_OT_clean_tracks);
diff --git a/source/blender/editors/space_clip/tracking_ops.c b/source/blender/editors/space_clip/tracking_ops.c
index 49313005c43..10574063ebd 100644
--- a/source/blender/editors/space_clip/tracking_ops.c
+++ b/source/blender/editors/space_clip/tracking_ops.c
@@ -1490,6 +1490,97 @@ void CLIP_OT_join_tracks(wmOperatorType *ot)
   ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
 }
 
+/********************** Average tracks operator *********************/
+
+static int average_tracks_exec(bContext *C, wmOperator *op)
+{
+  SpaceClip *space_clip = CTX_wm_space_clip(C);
+  MovieClip *clip = ED_space_clip_get_clip(space_clip);
+  MovieTracking *tracking = &clip->tracking;
+
+  /* Collect source tracks. */
+  int num_source_tracks;
+  MovieTrackingTrack **source_tracks = BKE_tracking_selected_tracks_in_active_object(
+      tracking, &num_source_tracks);
+  if (num_source_tracks == 0) {
+    return OPERATOR_CANCELLED;
+  }
+
+  /* Create new empty track, which will be the averaged result.
+   * Makes it simple to average all selection  to it. */
+  ListBase *tracks_list = BKE_tracking_get_active_tracks(tracking);
+  MovieTrackingTrack *result_track = BKE_tracking_track_add_empty(tracking, tracks_list);
+
+  /* Perform averaging. */
+  BKE_tracking_tracks_average(result_track, source_tracks, num_source_tracks);
+
+  const bool keep_original = RNA_boolean_get(op->ptr, "keep_original");
+  if (!keep_original) {
+    for (int i = 0; i < num_source_tracks; i++) {
+      clip_delete_track(C, clip, source_tracks[i]);
+    }
+  }
+
+  /* Update selection, making the result track active and selected. */
+  /* TODO(sergey): Should become some sort of utility function available for all operators. */
+
+  BKE_tracking_track_select(tracks_list, result_track, TRACK_AREA_ALL, 0);
+  ListBase *plane_tracks_list = BKE_tracking_get_active_plane_tracks(tracking);
+  BKE_tracking_plane_tracks_deselect_all(plane_tracks_list);
+
+  clip->tracking.act_track = result_track;
+  clip->tracking.act_plane_track = NULL;
+
+  /* Inform the dependency graph and interface about changes. */
+  DEG_id_tag_update(&clip->id, 0);
+  WM_event_add_notifier(C, NC_MOVIECLIP | NA_EDITED, clip);
+
+  /* Free memory. */
+  MEM_freeN(source_tracks);
+
+  return OPERATOR_FINISHED;
+}
+
+static int average_tracks_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
+{
+  PropertyRNA *prop_keep_original = RNA_struct_find_property(op->ptr, "keep_original");
+  if (!RNA_property_is_set(op->ptr, prop_keep_original)) {
+    SpaceClip *space_clip = CTX_wm_space_clip(C);
+    MovieClip *clip = ED_space_clip_get_clip(space_clip);
+    MovieTracking *tracking = &clip->tracking;
+
+    const int num_selected_tracks = BKE_tracking_count_selected_tracks_in_active_object(tracking);
+
+    if (num_selected_tracks == 1) {
+      RNA_property_boolean_set(op->ptr, prop_keep_original, false);
+    }
+  }
+
+  return average_tracks_exec(C, op);
+}
+
+void CLIP_OT_average_tracks(wmOperatorType *ot)
+{
+  /* Identifiers. */
+  ot->name = "Average Tracks";
+  ot->description = "Average selected tracks into active";
+  ot->idname = "CLIP_OT_average_tracks";
+
+  /* API callbacks. */
+  ot->exec = average_tracks_exec;
+  ot->invoke = average_tracks_invoke;
+  ot->poll = ED_space_clip_tracking_poll;
+
+  /* Flags. */
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+
+  /* Properties. */
+  PropertyRNA *prop;
+
+  prop = RNA_def_boolean(ot->srna, "keep_original", 1, "Keep Original", "Keep original tracks");
+  RNA_def_property_flag(prop, PROP_SKIP_SAVE);
+}
+
 /********************** lock tracks operator *********************/
 
 enum {