scripts/startup/bl_ui/space_graph.py

@@ -329,6 +329,7 @@ class GRAPH_MT_slider(Menu):
         layout.operator("graph.breakdown", text="Breakdown")
         layout.operator("graph.blend_to_neighbor", text="Blend to Neighbor")
         layout.operator("graph.blend_to_default", text="Blend to Default Value")
+        layout.operator("graph.blend_to_offset", text="Blend to Offset")
         layout.operator("graph.ease", text="Ease")
         layout.operator("graph.gaussian_smooth", text="Smooth")
 

source/blender/editors/animation/keyframes_general.c

@@ -491,6 +491,53 @@ void ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor
 
 /* ---------------- */
 
+void blend_to_offset_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor)
+{
+  const BezTriple *left_key = fcurve_segment_start_get(fcu, segment->start_index);
+  const float left_x = left_key->vec[1][0];
+  const float left_y = left_key->vec[1][1];
+
+  const BezTriple *right_key = fcurve_segment_end_get(fcu, segment->start_index + segment->length);
+  const float right_x = right_key->vec[1][0];
+  const float right_y = right_key->vec[1][1];
+
+  const BezTriple *segment_first_key = fcurve_segment_start_get(fcu, segment->start_index + 1);
+  const float segment_first_key_y = segment_first_key->vec[1][1];
+
+  const BezTriple *segment_last_key = fcurve_segment_end_get(fcu, segment->start_index + segment->length - 1);
+  const float segment_last_key_y = segment_last_key->vec[1][1];
+
+  const float key_x_range = right_x - left_x;
+
+  /* Happens if there is only 1 key on the FCurve. Needs to be skipped because it
+   * would be a divide by 0. */
+  if (IS_EQF(key_x_range, 0.0f)) {
+    return;
+  }
+
+  /* The calculation needs diferent values for each side of the slider. */
+  const bool slider_right_side = factor > 0.5;
+
+  /* For this tool the calculations are made easier if each side of the slider goes from 0 to porisive 1. */
+  const float ping_pong_factor = fabs(factor * 2 - 1);
+  
+  float y_delta = 0;
+
+  if (slider_right_side) {
+      y_delta = right_y - segment_last_key_y;
+    }
+    else {
+      y_delta = left_y - segment_first_key_y;
+    }
+
+  for (int i = segment->start_index; i < segment->start_index + segment->length; i++) {
+    const float key_y_value = fcu->bezt[i].vec[1][1] + y_delta * ping_pong_factor;
+    move_key(&fcu->bezt[i], key_y_value);
+  }
+}
+
+/* ---------------- */
+
 void breakdown_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor)
 {
   const BezTriple *left_bezt = fcurve_segment_start_get(fcu, segment->start_index);

source/blender/editors/include/ED_keyframes_edit.h

@@ -437,6 +437,7 @@ void smooth_fcurve_segment(struct FCurve *fcu,
                            int kernel_size,
                            double *kernel);
 void ease_fcurve_segment(struct FCurve *fcu, struct FCurveSegment *segment, float factor);
+void blend_to_offset_fcurve_segment(struct FCurve *fcu, struct FCurveSegment *segment, float factor);
 bool decimate_fcurve(struct bAnimListElem *ale, float remove_ratio, float error_sq_max);
 void blend_to_default_fcurve(struct PointerRNA *id_ptr, struct FCurve *fcu, float factor);
 /**

source/blender/editors/space_graph/graph_intern.h

@@ -114,6 +114,7 @@ void GRAPH_OT_clean(struct wmOperatorType *ot);
 void GRAPH_OT_blend_to_neighbor(struct wmOperatorType *ot);
 void GRAPH_OT_breakdown(struct wmOperatorType *ot);
 void GRAPH_OT_ease(struct wmOperatorType *ot);
+void GRAPH_OT_blend_to_offset(struct wmOperatorType *ot);
 void GRAPH_OT_decimate(struct wmOperatorType *ot);
 void GRAPH_OT_blend_to_default(struct wmOperatorType *ot);
 void GRAPH_OT_gaussian_smooth(struct wmOperatorType *ot);

source/blender/editors/space_graph/graph_ops.c

@@ -463,6 +463,7 @@ void graphedit_operatortypes(void)
   WM_operatortype_append(GRAPH_OT_blend_to_neighbor);
   WM_operatortype_append(GRAPH_OT_breakdown);
   WM_operatortype_append(GRAPH_OT_ease);
+  WM_operatortype_append(GRAPH_OT_blend_to_offset);
   WM_operatortype_append(GRAPH_OT_blend_to_default);
   WM_operatortype_append(GRAPH_OT_gaussian_smooth);
   WM_operatortype_append(GRAPH_OT_euler_filter);

source/blender/editors/space_graph/graph_slider_ops.c

@@ -1060,6 +1060,130 @@ void GRAPH_OT_ease(wmOperatorType *ot)
                        1.0f);
 }
 
+/* -------------------------------------------------------------------- */
+/** \name Blend to Offset Operator
+ * \{ */
+
+static void blend_to_offset_graph_keys(bAnimContext *ac, const float factor)
+{
+  ListBase anim_data = {NULL, NULL};
+
+  ANIM_animdata_filter(ac, &anim_data, OPERATOR_DATA_FILTER, ac->data, ac->datatype);
+  LISTBASE_FOREACH (bAnimListElem *, ale, &anim_data) {
+    FCurve *fcu = (FCurve *)ale->key_data;
+    ListBase segments = find_fcurve_segments(fcu);
+
+    LISTBASE_FOREACH (FCurveSegment *, segment, &segments) {
+      blend_to_offset_fcurve_segment(fcu, segment, factor);
+    }
+
+    ale->update |= ANIM_UPDATE_DEFAULT;
+    BLI_freelistN(&segments);
+  }
+
+  ANIM_animdata_update(ac, &anim_data);
+  ANIM_animdata_freelist(&anim_data);
+}
+
+static void blend_to_offset_draw_status_header(bContext *C, tGraphSliderOp *gso)
+{
+  char status_str[UI_MAX_DRAW_STR];
+  char mode_str[32];
+  char slider_string[UI_MAX_DRAW_STR];
+
+  ED_slider_status_string_get(gso->slider, slider_string, UI_MAX_DRAW_STR);
+
+  strcpy(mode_str, TIP_("Blend to Offset Keys"));
+
+  if (hasNumInput(&gso->num)) {
+    char str_ofs[NUM_STR_REP_LEN];
+
+    outputNumInput(&gso->num, str_ofs, &gso->scene->unit);
+
+    BLI_snprintf(status_str, sizeof(status_str), "%s: %s", mode_str, str_ofs);
+  }
+  else {
+    BLI_snprintf(status_str, sizeof(status_str), "%s: %s", mode_str, slider_string);
+  }
+
+  ED_workspace_status_text(C, status_str);
+}
+
+static void blend_to_offset_modal_update(bContext *C, wmOperator *op)
+{
+  tGraphSliderOp *gso = op->customdata;
+
+  blend_to_offset_draw_status_header(C, gso);
+
+  /* Reset keyframes to the state at invoke. */
+  reset_bezts(gso);
+  const float factor = slider_factor_get_and_remember(op);
+  blend_to_offset_graph_keys(&gso->ac, factor);
+  WM_event_add_notifier(C, NC_ANIMATION | ND_KEYFRAME | NA_EDITED, NULL);
+}
+
+static int blend_to_offset_invoke(bContext *C, wmOperator *op, const wmEvent *event)
+{
+  const int invoke_result = graph_slider_invoke(C, op, event);
+
+  if (invoke_result == OPERATOR_CANCELLED) {
+    return invoke_result;
+  }
+
+  tGraphSliderOp *gso = op->customdata;
+  gso->modal_update = blend_to_offset_modal_update;
+  gso->factor_prop = RNA_struct_find_property(op->ptr, "factor");
+  blend_to_offset_draw_status_header(C, gso);
+
+  return invoke_result;
+}
+
+static int blend_to_offset_exec(bContext *C, wmOperator *op)
+{
+  bAnimContext ac;
+
+  /* Get editor data. */
+  if (ANIM_animdata_get_context(C, &ac) == 0) {
+    return OPERATOR_CANCELLED;
+  }
+
+  const float factor = RNA_float_get(op->ptr, "factor");
+
+  blend_to_offset_graph_keys(&ac, factor);
+
+  /* Set notifier that keyframes have changed. */
+  WM_event_add_notifier(C, NC_ANIMATION | ND_KEYFRAME | NA_EDITED, NULL);
+
+  return OPERATOR_FINISHED;
+}
+
+void GRAPH_OT_blend_to_offset(wmOperatorType *ot)
+{
+  /* Identifiers. */
+  ot->name = "Blend to Offset Keyframes";
+  ot->idname = "GRAPH_OT_blend_to_offset";
+  ot->description = "Shift selected keys to the value of the neighboring keys as a block";
+
+  /* API callbacks. */
+  ot->invoke = blend_to_offset_invoke;
+  ot->modal = graph_slider_modal;
+  ot->exec = blend_to_offset_exec;
+  ot->poll = graphop_editable_keyframes_poll;
+
+  /* Flags. */
+  ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+
+  RNA_def_float_factor(ot->srna,
+                       "factor",
+                       0.5f,
+                       -FLT_MAX,
+                       FLT_MAX,
+                       "Curve Bend",
+                       "Control the bend of the curve",
+                       0.0f,
+                       1.0f);
+}
+
 /** \} */
 /* -------------------------------------------------------------------- */
 /** \name Gauss Smooth Operator