From 9d1c03966bca72f33368c69490c8d94563147887 Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Sun, 2 Apr 2023 20:09:47 -0700
Subject: [PATCH 01/11] Added functions

---
 scripts/startup/bl_ui/space_graph.py          |   1 +
 .../editors/animation/keyframes_general.c     |  64 +++++++++
 .../editors/include/ED_keyframes_edit.h       |   1 +
 .../editors/space_graph/graph_intern.h        |   1 +
 .../blender/editors/space_graph/graph_ops.c   |   1 +
 .../editors/space_graph/graph_slider_ops.c    | 124 ++++++++++++++++++
 6 files changed, 192 insertions(+)

diff --git a/scripts/startup/bl_ui/space_graph.py b/scripts/startup/bl_ui/space_graph.py
index 999a9e3cef7..3b7a93d798f 100644
--- a/scripts/startup/bl_ui/space_graph.py
+++ b/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_ease", text="Blend to Ease")
         layout.operator("graph.ease", text="Ease")
         layout.operator("graph.gaussian_smooth", text="Smooth")
 
diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index f1848e4cc42..70d5cdff3d8 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -491,6 +491,70 @@ void ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor
 
 /* ---------------- */
 
+float s_curve(float x, float slope, float width, float height, float xshift, float yshift) {
+    /* Formula for 'S' curve we use for the "ease" sliders. The shift values move the curve vertiacly or horizontaly.
+     * The range of the curve used is from 0 to 1 on "x" and "y" so we can scale it (width and height) and move it (xshift and y yshift) 
+     * to crop the part of the curve we need. Slope determins how curvy the shape is */
+    float curve = height * pow((x - xshift), slope) / (pow((x - xshift), slope) + pow((width - (x - xshift)), slope)) + yshift;
+
+    /* The curve has some noise beyond our margins so we clamp the values */
+    if (x > xshift + width) {
+        curve = height + yshift;
+    } else if (x < xshift) {
+        curve = yshift;
+    }
+    return curve;
+}
+
+void ease_b_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 key_x_range = right_key->vec[1][0] - left_x;
+  const float key_y_range = right_key->vec[1][1] - left_y;
+
+  /* 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;
+
+  /* The factor goes from 0 to 1, but for this tool it needs to go from 0 to 1 on each side of the slider. */
+  const float ping_pong_factor = fabs(factor * 2 - 1) * 5;
+
+  /* By duplicating the size of the curve we get only half of the "S" shape (kind of a "C" shape). */
+  const float width = 2.0;
+  const float height = 2.0;
+  float xshift = 0.0;
+  float yshift = 0.0;
+
+  for (int i = segment->start_index; i < segment->start_index + segment->length; i++) {
+    /* For easy calculation of the curve, the  values are normalized. */
+    const float normalized_x = (fcu->bezt[i].vec[1][0] - left_key->vec[1][0]) / key_x_range;
+
+    /* For values on the right side of the slider we need the other half of the "S" shape. */
+    if (slider_right_side) {
+      xshift = -1.0;
+      yshift = -1.0;
+    }
+
+    /* The factor is used to affect the slope of the the "C" shape. */
+    float ease = s_curve(normalized_x, ping_pong_factor, width, height, xshift, yshift);
+
+    const float key_y_value = left_key->vec[1][1] + key_y_range * ease;
+    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);
diff --git a/source/blender/editors/include/ED_keyframes_edit.h b/source/blender/editors/include/ED_keyframes_edit.h
index 69f103c6cba..dd631b724e0 100644
--- a/source/blender/editors/include/ED_keyframes_edit.h
+++ b/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_ease_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);
 /**
diff --git a/source/blender/editors/space_graph/graph_intern.h b/source/blender/editors/space_graph/graph_intern.h
index 7128f805a23..013620fd854 100644
--- a/source/blender/editors/space_graph/graph_intern.h
+++ b/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_ease(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);
diff --git a/source/blender/editors/space_graph/graph_ops.c b/source/blender/editors/space_graph/graph_ops.c
index b64884da06c..350afb38f5b 100644
--- a/source/blender/editors/space_graph/graph_ops.c
+++ b/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_ease);
   WM_operatortype_append(GRAPH_OT_blend_to_default);
   WM_operatortype_append(GRAPH_OT_gaussian_smooth);
   WM_operatortype_append(GRAPH_OT_euler_filter);
diff --git a/source/blender/editors/space_graph/graph_slider_ops.c b/source/blender/editors/space_graph/graph_slider_ops.c
index 184bd8329e8..e7347903596 100644
--- a/source/blender/editors/space_graph/graph_slider_ops.c
+++ b/source/blender/editors/space_graph/graph_slider_ops.c
@@ -1060,6 +1060,130 @@ void GRAPH_OT_ease(wmOperatorType *ot)
                        1.0f);
 }
 
+/* -------------------------------------------------------------------- */
+/** \name Blend Ease Operator
+ * \{ */
+
+static void blend_ease_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_ease_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_ease_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 Ease 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_ease_modal_update(bContext *C, wmOperator *op)
+{
+  tGraphSliderOp *gso = op->customdata;
+
+  blend_ease_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_ease_graph_keys(&gso->ac, factor);
+  WM_event_add_notifier(C, NC_ANIMATION | ND_KEYFRAME | NA_EDITED, NULL);
+}
+
+static int blend_ease_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_ease_modal_update;
+  gso->factor_prop = RNA_struct_find_property(op->ptr, "factor");
+  blend_ease_draw_status_header(C, gso);
+
+  return invoke_result;
+}
+
+static int blend_ease_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_ease_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_ease(wmOperatorType *ot)
+{
+  /* Identifiers. */
+  ot->name = "Blend Ease Keyframes";
+  ot->idname = "GRAPH_OT_blend_ease";
+  ot->description = "Align keyframes on a ease-in or ease-out curve";
+
+  /* API callbacks. */
+  ot->invoke = blend_ease_invoke;
+  ot->modal = graph_slider_modal;
+  ot->exec = blend_ease_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
-- 
2.30.2


From cb45fcb306c1c1bdbd04e841240a854dd3f72871 Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Sun, 2 Apr 2023 20:28:40 -0700
Subject: [PATCH 02/11] change names of the functions to include "to" and fixed
 one functions that was actually the wrong one

---
 scripts/startup/bl_ui/space_graph.py          |  2 +-
 .../editors/animation/keyframes_general.c     | 33 ++++++++--------
 .../editors/include/ED_keyframes_edit.h       |  2 +-
 .../editors/space_graph/graph_intern.h        |  2 +-
 .../blender/editors/space_graph/graph_ops.c   |  2 +-
 .../editors/space_graph/graph_slider_ops.c    | 38 +++++++++----------
 6 files changed, 40 insertions(+), 39 deletions(-)

diff --git a/scripts/startup/bl_ui/space_graph.py b/scripts/startup/bl_ui/space_graph.py
index 3b7a93d798f..38ef96fe3ad 100644
--- a/scripts/startup/bl_ui/space_graph.py
+++ b/scripts/startup/bl_ui/space_graph.py
@@ -329,7 +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_ease", text="Blend to Ease")
+        layout.operator("graph.blend_to_ease", text="Blend to Ease")
         layout.operator("graph.ease", text="Ease")
         layout.operator("graph.gaussian_smooth", text="Smooth")
 
diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index 70d5cdff3d8..fc48807ba1c 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -506,7 +506,7 @@ float s_curve(float x, float slope, float width, float height, float xshift, flo
     return curve;
 }
 
-void ease_b_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor)
+void blend_to_ease_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];
@@ -515,7 +515,7 @@ void ease_b_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float fact
   const BezTriple *right_key = fcurve_segment_end_get(fcu, segment->start_index + segment->length);
 
   const float key_x_range = right_key->vec[1][0] - left_x;
-  const float key_y_range = right_key->vec[1][1] - left_y;
+  const float key_y_range = right_key->vec[1][1] - left_x;
 
   /* Happens if there is only 1 key on the FCurve. Needs to be skipped because it
    * would be a divide by 0. */
@@ -526,29 +526,30 @@ void ease_b_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float fact
   /* The calculation needs diferent values for each side of the slider. */
   const bool slider_right_side = factor > 0.5;
 
-  /* The factor goes from 0 to 1, but for this tool it needs to go from 0 to 1 on each side of the slider. */
-  const float ping_pong_factor = fabs(factor * 2 - 1) * 5;
+  /* The factor goes from 0 to 1, but for this tool it needs to go from -1 to 1. */
+  const float long_factor =  factor * 2 - 1;
+
+  float y_delta = 0;
+  float base = 0;
 
-  /* By duplicating the size of the curve we get only half of the "S" shape (kind of a "C" shape). */
-  const float width = 2.0;
-  const float height = 2.0;
-  float xshift = 0.0;
-  float yshift = 0.0;
 
   for (int i = segment->start_index; i < segment->start_index + segment->length; i++) {
     /* For easy calculation of the curve, the  values are normalized. */
     const float normalized_x = (fcu->bezt[i].vec[1][0] - left_key->vec[1][0]) / key_x_range;
 
-    /* For values on the right side of the slider we need the other half of the "S" shape. */
+
     if (slider_right_side) {
-      xshift = -1.0;
-      yshift = -1.0;
+      float ease = s_curve(normalized_x, 3, 2.0, 2.0, -1.0, -1.0);
+      base = left_key->vec[1][1] + key_y_range * ease;
+      y_delta = base - fcu->bezt[i].vec[1][1];
+    }
+    else {
+      float ease = s_curve(normalized_x, 3, 2.0, 2.0, 0.0, 0.0);
+      base = left_key->vec[1][1] + key_y_range * ease;
+      y_delta = fcu->bezt[i].vec[1][1] - base;
     }
 
-    /* The factor is used to affect the slope of the the "C" shape. */
-    float ease = s_curve(normalized_x, ping_pong_factor, width, height, xshift, yshift);
-
-    const float key_y_value = left_key->vec[1][1] + key_y_range * ease;
+    const float key_y_value = fcu->bezt[i].vec[1][1] + y_delta * long_factor;
     move_key(&fcu->bezt[i], key_y_value);
   }
 }
diff --git a/source/blender/editors/include/ED_keyframes_edit.h b/source/blender/editors/include/ED_keyframes_edit.h
index dd631b724e0..fc2f249369a 100644
--- a/source/blender/editors/include/ED_keyframes_edit.h
+++ b/source/blender/editors/include/ED_keyframes_edit.h
@@ -437,7 +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_ease_fcurve_segment(struct FCurve *fcu, struct FCurveSegment *segment, float factor);
+void blend_to_ease_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);
 /**
diff --git a/source/blender/editors/space_graph/graph_intern.h b/source/blender/editors/space_graph/graph_intern.h
index 013620fd854..0ee281ac403 100644
--- a/source/blender/editors/space_graph/graph_intern.h
+++ b/source/blender/editors/space_graph/graph_intern.h
@@ -114,7 +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_ease(struct wmOperatorType *ot);
+void GRAPH_OT_blend_to_ease(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);
diff --git a/source/blender/editors/space_graph/graph_ops.c b/source/blender/editors/space_graph/graph_ops.c
index 350afb38f5b..646a432ad2e 100644
--- a/source/blender/editors/space_graph/graph_ops.c
+++ b/source/blender/editors/space_graph/graph_ops.c
@@ -463,7 +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_ease);
+  WM_operatortype_append(GRAPH_OT_blend_to_ease);
   WM_operatortype_append(GRAPH_OT_blend_to_default);
   WM_operatortype_append(GRAPH_OT_gaussian_smooth);
   WM_operatortype_append(GRAPH_OT_euler_filter);
diff --git a/source/blender/editors/space_graph/graph_slider_ops.c b/source/blender/editors/space_graph/graph_slider_ops.c
index e7347903596..b78ccdf6e63 100644
--- a/source/blender/editors/space_graph/graph_slider_ops.c
+++ b/source/blender/editors/space_graph/graph_slider_ops.c
@@ -1061,10 +1061,10 @@ void GRAPH_OT_ease(wmOperatorType *ot)
 }
 
 /* -------------------------------------------------------------------- */
-/** \name Blend Ease Operator
+/** \name Blend to Ease Operator
  * \{ */
 
-static void blend_ease_graph_keys(bAnimContext *ac, const float factor)
+static void blend_to_ease_graph_keys(bAnimContext *ac, const float factor)
 {
   ListBase anim_data = {NULL, NULL};
 
@@ -1074,7 +1074,7 @@ static void blend_ease_graph_keys(bAnimContext *ac, const float factor)
     ListBase segments = find_fcurve_segments(fcu);
 
     LISTBASE_FOREACH (FCurveSegment *, segment, &segments) {
-      blend_ease_fcurve_segment(fcu, segment, factor);
+      blend_to_ease_fcurve_segment(fcu, segment, factor);
     }
 
     ale->update |= ANIM_UPDATE_DEFAULT;
@@ -1085,7 +1085,7 @@ static void blend_ease_graph_keys(bAnimContext *ac, const float factor)
   ANIM_animdata_freelist(&anim_data);
 }
 
-static void blend_ease_draw_status_header(bContext *C, tGraphSliderOp *gso)
+static void blend_to_ease_draw_status_header(bContext *C, tGraphSliderOp *gso)
 {
   char status_str[UI_MAX_DRAW_STR];
   char mode_str[32];
@@ -1093,7 +1093,7 @@ static void blend_ease_draw_status_header(bContext *C, tGraphSliderOp *gso)
 
   ED_slider_status_string_get(gso->slider, slider_string, UI_MAX_DRAW_STR);
 
-  strcpy(mode_str, TIP_("Blend Ease Keys"));
+  strcpy(mode_str, TIP_("Blend to Ease Keys"));
 
   if (hasNumInput(&gso->num)) {
     char str_ofs[NUM_STR_REP_LEN];
@@ -1109,20 +1109,20 @@ static void blend_ease_draw_status_header(bContext *C, tGraphSliderOp *gso)
   ED_workspace_status_text(C, status_str);
 }
 
-static void blend_ease_modal_update(bContext *C, wmOperator *op)
+static void blend_to_ease_modal_update(bContext *C, wmOperator *op)
 {
   tGraphSliderOp *gso = op->customdata;
 
-  blend_ease_draw_status_header(C, gso);
+  blend_to_ease_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_ease_graph_keys(&gso->ac, factor);
+  blend_to_ease_graph_keys(&gso->ac, factor);
   WM_event_add_notifier(C, NC_ANIMATION | ND_KEYFRAME | NA_EDITED, NULL);
 }
 
-static int blend_ease_invoke(bContext *C, wmOperator *op, const wmEvent *event)
+static int blend_to_ease_invoke(bContext *C, wmOperator *op, const wmEvent *event)
 {
   const int invoke_result = graph_slider_invoke(C, op, event);
 
@@ -1131,14 +1131,14 @@ static int blend_ease_invoke(bContext *C, wmOperator *op, const wmEvent *event)
   }
 
   tGraphSliderOp *gso = op->customdata;
-  gso->modal_update = blend_ease_modal_update;
+  gso->modal_update = blend_to_ease_modal_update;
   gso->factor_prop = RNA_struct_find_property(op->ptr, "factor");
-  blend_ease_draw_status_header(C, gso);
+  blend_to_ease_draw_status_header(C, gso);
 
   return invoke_result;
 }
 
-static int blend_ease_exec(bContext *C, wmOperator *op)
+static int blend_to_ease_exec(bContext *C, wmOperator *op)
 {
   bAnimContext ac;
 
@@ -1149,7 +1149,7 @@ static int blend_ease_exec(bContext *C, wmOperator *op)
 
   const float factor = RNA_float_get(op->ptr, "factor");
 
-  blend_ease_graph_keys(&ac, factor);
+  blend_to_ease_graph_keys(&ac, factor);
 
   /* Set notifier that keyframes have changed. */
   WM_event_add_notifier(C, NC_ANIMATION | ND_KEYFRAME | NA_EDITED, NULL);
@@ -1157,17 +1157,17 @@ static int blend_ease_exec(bContext *C, wmOperator *op)
   return OPERATOR_FINISHED;
 }
 
-void GRAPH_OT_blend_ease(wmOperatorType *ot)
+void GRAPH_OT_blend_to_ease(wmOperatorType *ot)
 {
   /* Identifiers. */
-  ot->name = "Blend Ease Keyframes";
-  ot->idname = "GRAPH_OT_blend_ease";
-  ot->description = "Align keyframes on a ease-in or ease-out curve";
+  ot->name = "Blend to Ease Keyframes";
+  ot->idname = "GRAPH_OT_blend_to_ease";
+  ot->description = "Blends keyframes from current state to an ease-in or ease-out curve";
 
   /* API callbacks. */
-  ot->invoke = blend_ease_invoke;
+  ot->invoke = blend_to_ease_invoke;
   ot->modal = graph_slider_modal;
-  ot->exec = blend_ease_exec;
+  ot->exec = blend_to_ease_exec;
   ot->poll = graphop_editable_keyframes_poll;
 
   /* Flags. */
-- 
2.30.2


From 6ddc483989e6713a4af0d61bd27b389b86181bfe Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Sun, 2 Apr 2023 22:57:45 -0700
Subject: [PATCH 03/11] changed some variables to constant

---
 source/blender/editors/animation/keyframes_general.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index fc48807ba1c..78c58e1e961 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -530,8 +530,6 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
   const float long_factor =  factor * 2 - 1;
 
   float y_delta = 0;
-  float base = 0;
-
 
   for (int i = segment->start_index; i < segment->start_index + segment->length; i++) {
     /* For easy calculation of the curve, the  values are normalized. */
@@ -540,13 +538,13 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
 
     if (slider_right_side) {
       float ease = s_curve(normalized_x, 3, 2.0, 2.0, -1.0, -1.0);
-      base = left_key->vec[1][1] + key_y_range * ease;
-      y_delta = base - fcu->bezt[i].vec[1][1];
+      const float base = left_key->vec[1][1] + key_y_range * ease;
+      const float y_delta = base - fcu->bezt[i].vec[1][1];
     }
     else {
       float ease = s_curve(normalized_x, 3, 2.0, 2.0, 0.0, 0.0);
-      base = left_key->vec[1][1] + key_y_range * ease;
-      y_delta = fcu->bezt[i].vec[1][1] - base;
+      const float base = left_key->vec[1][1] + key_y_range * ease;
+      const float y_delta = fcu->bezt[i].vec[1][1] - base;
     }
 
     const float key_y_value = fcu->bezt[i].vec[1][1] + y_delta * long_factor;
-- 
2.30.2


From 1ef18cc8c70b7cbdb7d581eb939090e51940a4b2 Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Sun, 2 Apr 2023 23:07:09 -0700
Subject: [PATCH 04/11] changed some variables declaration

---
 source/blender/editors/animation/keyframes_general.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index 78c58e1e961..cda560ba43f 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -529,7 +529,7 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
   /* The factor goes from 0 to 1, but for this tool it needs to go from -1 to 1. */
   const float long_factor =  factor * 2 - 1;
 
-  float y_delta = 0;
+  float y_delta;
 
   for (int i = segment->start_index; i < segment->start_index + segment->length; i++) {
     /* For easy calculation of the curve, the  values are normalized. */
@@ -537,14 +537,14 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
 
 
     if (slider_right_side) {
-      float ease = s_curve(normalized_x, 3, 2.0, 2.0, -1.0, -1.0);
+      const float ease = s_curve(normalized_x, 3, 2.0, 2.0, -1.0, -1.0);
       const float base = left_key->vec[1][1] + key_y_range * ease;
-      const float y_delta = base - fcu->bezt[i].vec[1][1];
+      y_delta = base - fcu->bezt[i].vec[1][1];
     }
     else {
-      float ease = s_curve(normalized_x, 3, 2.0, 2.0, 0.0, 0.0);
+      const float ease = s_curve(normalized_x, 3, 2.0, 2.0, 0.0, 0.0);
       const float base = left_key->vec[1][1] + key_y_range * ease;
-      const float y_delta = fcu->bezt[i].vec[1][1] - base;
+      y_delta = fcu->bezt[i].vec[1][1] - base;
     }
 
     const float key_y_value = fcu->bezt[i].vec[1][1] + y_delta * long_factor;
-- 
2.30.2


From 181c5389ebeb124d05f3d1d2e18999afd3c5ec49 Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Mon, 3 Apr 2023 10:57:08 -0700
Subject: [PATCH 05/11] Fixed some formating

---
 .../editors/animation/keyframes_general.c     | 32 +++++++++++--------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index cda560ba43f..f96c0e5f1c7 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -491,19 +491,24 @@ void ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor
 
 /* ---------------- */
 
-float s_curve(float x, float slope, float width, float height, float xshift, float yshift) {
-    /* Formula for 'S' curve we use for the "ease" sliders. The shift values move the curve vertiacly or horizontaly.
-     * The range of the curve used is from 0 to 1 on "x" and "y" so we can scale it (width and height) and move it (xshift and y yshift) 
-     * to crop the part of the curve we need. Slope determins how curvy the shape is */
-    float curve = height * pow((x - xshift), slope) / (pow((x - xshift), slope) + pow((width - (x - xshift)), slope)) + yshift;
+float s_curve(float x, float slope, float width, float height, float xshift, float yshift)
+{
+  /* Formula for 'S' curve we use for the "ease" sliders. The shift values move the curve vertiacly
+   * or horizontaly. The range of the curve used is from 0 to 1 on "x" and "y" so we can scale it
+   * (width and height) and move it (xshift and y yshift) to crop the part of the curve we need.
+   * Slope determins how curvy the shape is */
+  float curve = height * pow((x - xshift), slope) /
+                    (pow((x - xshift), slope) + pow((width - (x - xshift)), slope)) +
+                yshift;
 
-    /* The curve has some noise beyond our margins so we clamp the values */
-    if (x > xshift + width) {
-        curve = height + yshift;
-    } else if (x < xshift) {
-        curve = yshift;
-    }
-    return curve;
+  /* The curve has some noise beyond our margins so we clamp the values */
+  if (x > xshift + width) {
+    curve = height + yshift;
+  }
+  else if (x < xshift) {
+    curve = yshift;
+  }
+  return curve;
 }
 
 void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor)
@@ -527,7 +532,7 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
   const bool slider_right_side = factor > 0.5;
 
   /* The factor goes from 0 to 1, but for this tool it needs to go from -1 to 1. */
-  const float long_factor =  factor * 2 - 1;
+  const float long_factor = factor * 2 - 1;
 
   float y_delta;
 
@@ -535,7 +540,6 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
     /* For easy calculation of the curve, the  values are normalized. */
     const float normalized_x = (fcu->bezt[i].vec[1][0] - left_key->vec[1][0]) / key_x_range;
 
-
     if (slider_right_side) {
       const float ease = s_curve(normalized_x, 3, 2.0, 2.0, -1.0, -1.0);
       const float base = left_key->vec[1][1] + key_y_range * ease;
-- 
2.30.2


From 1e5227c635ab4f595e1d65fce012d63430fc5c51 Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Mon, 10 Apr 2023 16:04:42 -0700
Subject: [PATCH 06/11] simplified the function and fixed an error

---
 source/blender/editors/animation/keyframes_general.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index f96c0e5f1c7..85239a2a8dc 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -491,7 +491,7 @@ void ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor
 
 /* ---------------- */
 
-float s_curve(float x, float slope, float width, float height, float xshift, float yshift)
+static float s_curve(float x, float slope, float width, float height, float xshift, float yshift)
 {
   /* Formula for 'S' curve we use for the "ease" sliders. The shift values move the curve vertiacly
    * or horizontaly. The range of the curve used is from 0 to 1 on "x" and "y" so we can scale it
@@ -514,13 +514,10 @@ float s_curve(float x, float slope, float width, float height, float xshift, flo
 void blend_to_ease_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 key_x_range = right_key->vec[1][0] - left_x;
-  const float key_y_range = right_key->vec[1][1] - left_x;
+  const float key_x_range = right_key->vec[1][0] - left_key->vec[1][0];
+  const float key_y_range = right_key->vec[1][1] - left_key->vec[1][1];
 
   /* Happens if there is only 1 key on the FCurve. Needs to be skipped because it
    * would be a divide by 0. */
-- 
2.30.2


From c17a5dda7fb0d676952196b2b466307fac0160eb Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Fri, 14 Apr 2023 11:29:21 -0700
Subject: [PATCH 07/11] addressed Christoph's notes to change variable name and
 simplify

---
 .../editors/animation/keyframes_general.c       | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index 85239a2a8dc..c1e26640c2e 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -497,18 +497,18 @@ static float s_curve(float x, float slope, float width, float height, float xshi
    * or horizontaly. The range of the curve used is from 0 to 1 on "x" and "y" so we can scale it
    * (width and height) and move it (xshift and y yshift) to crop the part of the curve we need.
    * Slope determins how curvy the shape is */
-  float curve = height * pow((x - xshift), slope) /
-                    (pow((x - xshift), slope) + pow((width - (x - xshift)), slope)) +
-                yshift;
+  float y = height * pow((x - xshift), slope) /
+                (pow((x - xshift), slope) + pow((width - (x - xshift)), slope)) +
+            yshift;
 
   /* The curve has some noise beyond our margins so we clamp the values */
   if (x > xshift + width) {
-    curve = height + yshift;
+    y = height + yshift;
   }
   else if (x < xshift) {
-    curve = yshift;
+    y = yshift;
   }
-  return curve;
+  return y;
 }
 
 void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor)
@@ -525,9 +525,6 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
     return;
   }
 
-  /* The calculation needs diferent values for each side of the slider. */
-  const bool slider_right_side = factor > 0.5;
-
   /* The factor goes from 0 to 1, but for this tool it needs to go from -1 to 1. */
   const float long_factor = factor * 2 - 1;
 
@@ -537,7 +534,7 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
     /* For easy calculation of the curve, the  values are normalized. */
     const float normalized_x = (fcu->bezt[i].vec[1][0] - left_key->vec[1][0]) / key_x_range;
 
-    if (slider_right_side) {
+    if (factor > 0.5) {
       const float ease = s_curve(normalized_x, 3, 2.0, 2.0, -1.0, -1.0);
       const float base = left_key->vec[1][1] + key_y_range * ease;
       y_delta = base - fcu->bezt[i].vec[1][1];
-- 
2.30.2


From 90fdaf9ad7c8f562e33c7982697b90902ff82308 Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Mon, 17 Apr 2023 22:06:14 -0700
Subject: [PATCH 08/11] converted the slider to bidirectional and disabled the
 offset

---
 source/blender/editors/animation/keyframes_general.c  | 7 ++-----
 source/blender/editors/space_graph/graph_slider_ops.c | 3 +++
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index c1e26640c2e..a1777d37892 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -525,16 +525,13 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
     return;
   }
 
-  /* The factor goes from 0 to 1, but for this tool it needs to go from -1 to 1. */
-  const float long_factor = factor * 2 - 1;
-
   float y_delta;
 
   for (int i = segment->start_index; i < segment->start_index + segment->length; i++) {
     /* For easy calculation of the curve, the  values are normalized. */
     const float normalized_x = (fcu->bezt[i].vec[1][0] - left_key->vec[1][0]) / key_x_range;
 
-    if (factor > 0.5) {
+    if (factor > 0) {
       const float ease = s_curve(normalized_x, 3, 2.0, 2.0, -1.0, -1.0);
       const float base = left_key->vec[1][1] + key_y_range * ease;
       y_delta = base - fcu->bezt[i].vec[1][1];
@@ -545,7 +542,7 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
       y_delta = fcu->bezt[i].vec[1][1] - base;
     }
 
-    const float key_y_value = fcu->bezt[i].vec[1][1] + y_delta * long_factor;
+    const float key_y_value = fcu->bezt[i].vec[1][1] + y_delta * factor;
     move_key(&fcu->bezt[i], key_y_value);
   }
 }
diff --git a/source/blender/editors/space_graph/graph_slider_ops.c b/source/blender/editors/space_graph/graph_slider_ops.c
index b78ccdf6e63..c379353c879 100644
--- a/source/blender/editors/space_graph/graph_slider_ops.c
+++ b/source/blender/editors/space_graph/graph_slider_ops.c
@@ -1134,6 +1134,9 @@ static int blend_to_ease_invoke(bContext *C, wmOperator *op, const wmEvent *even
   gso->modal_update = blend_to_ease_modal_update;
   gso->factor_prop = RNA_struct_find_property(op->ptr, "factor");
   blend_to_ease_draw_status_header(C, gso);
+  ED_slider_allow_overshoot_set(gso->slider, false);
+  ED_slider_is_bidirectional_set(gso->slider, true);
+  ED_slider_factor_set(gso->slider, 0.0f);
 
   return invoke_result;
 }
-- 
2.30.2


From 5a2d9b9012d50d5bf19e35d90acb62eff9362f63 Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Wed, 19 Apr 2023 01:52:19 -0700
Subject: [PATCH 09/11] removed magic numbers and took some lines out of the
 loop

---
 .../editors/animation/keyframes_general.c     | 21 +++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index a1777d37892..02801a44759 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -525,20 +525,29 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
     return;
   }
 
+  const float slope = 3.0;
+  const float width = 2.0;
+  const float height = 2.0;
+  float xy_shift;
   float y_delta;
 
+  if (factor > 0) {
+    xy_shift = -1.0;
+  }
+  else {
+    xy_shift = 0.0;
+  }
+
   for (int i = segment->start_index; i < segment->start_index + segment->length; i++) {
-    /* For easy calculation of the curve, the  values are normalized. */
-    const float normalized_x = (fcu->bezt[i].vec[1][0] - left_key->vec[1][0]) / key_x_range;
+    
+    const float x = (fcu->bezt[i].vec[1][0] - left_key->vec[1][0]) / key_x_range;
+    const float ease = s_curve(x, slope, width, height, xy_shift, xy_shift);
+    const float base = left_key->vec[1][1] + key_y_range * ease;
 
     if (factor > 0) {
-      const float ease = s_curve(normalized_x, 3, 2.0, 2.0, -1.0, -1.0);
-      const float base = left_key->vec[1][1] + key_y_range * ease;
       y_delta = base - fcu->bezt[i].vec[1][1];
     }
     else {
-      const float ease = s_curve(normalized_x, 3, 2.0, 2.0, 0.0, 0.0);
-      const float base = left_key->vec[1][1] + key_y_range * ease;
       y_delta = fcu->bezt[i].vec[1][1] - base;
     }
 
-- 
2.30.2


From f898da502269d686c3a7310aff3804255f5df595 Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Wed, 19 Apr 2023 02:05:23 -0700
Subject: [PATCH 10/11] added some comments

---
 source/blender/editors/animation/keyframes_general.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/source/blender/editors/animation/keyframes_general.c b/source/blender/editors/animation/keyframes_general.c
index 02801a44759..ee602d92d6a 100644
--- a/source/blender/editors/animation/keyframes_general.c
+++ b/source/blender/editors/animation/keyframes_general.c
@@ -493,7 +493,7 @@ void ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const float factor
 
 static float s_curve(float x, float slope, float width, float height, float xshift, float yshift)
 {
-  /* Formula for 'S' curve we use for the "ease" sliders. The shift values move the curve vertiacly
+  /* Formula for 'S' curve we use for the "ease" sliders. The shift values move the curve verticaly
    * or horizontaly. The range of the curve used is from 0 to 1 on "x" and "y" so we can scale it
    * (width and height) and move it (xshift and y yshift) to crop the part of the curve we need.
    * Slope determins how curvy the shape is */
@@ -526,11 +526,13 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
   }
 
   const float slope = 3.0;
+  /* By doubling the size of the "S" curve we just one side of it, a "C" shape. */
   const float width = 2.0;
   const float height = 2.0;
   float xy_shift;
   float y_delta;
 
+  /* Shifting the x and y values we can decide what side of the "S" shape to use. */
   if (factor > 0) {
     xy_shift = -1.0;
   }
@@ -539,7 +541,7 @@ void blend_to_ease_fcurve_segment(FCurve *fcu, FCurveSegment *segment, const flo
   }
 
   for (int i = segment->start_index; i < segment->start_index + segment->length; i++) {
-    
+
     const float x = (fcu->bezt[i].vec[1][0] - left_key->vec[1][0]) / key_x_range;
     const float ease = s_curve(x, slope, width, height, xy_shift, xy_shift);
     const float base = left_key->vec[1][1] + key_y_range * ease;
-- 
2.30.2


From 27ae422111c15e08ce0ca1dc6eeee793b5a485a6 Mon Sep 17 00:00:00 2001
From: Ares Deveaux <aresdevo@gmail.com>
Date: Thu, 20 Apr 2023 12:45:13 -0700
Subject: [PATCH 11/11] corrected a small error in the operator

---
 source/blender/editors/space_graph/graph_slider_ops.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/source/blender/editors/space_graph/graph_slider_ops.c b/source/blender/editors/space_graph/graph_slider_ops.c
index c379353c879..181c9b90d9c 100644
--- a/source/blender/editors/space_graph/graph_slider_ops.c
+++ b/source/blender/editors/space_graph/graph_slider_ops.c
@@ -1178,12 +1178,12 @@ void GRAPH_OT_blend_to_ease(wmOperatorType *ot)
 
   RNA_def_float_factor(ot->srna,
                        "factor",
-                       0.5f,
+                       0.0f,
                        -FLT_MAX,
                        FLT_MAX,
                        "Curve Bend",
                        "Control the bend of the curve",
-                       0.0f,
+                       -1.0f,
                        1.0f);
 }
 
-- 
2.30.2