From 71fd0f7b7b0a136511949e25a185d90f5738749e Mon Sep 17 00:00:00 2001
From: Cian Jinks <cjinks99@gmail.com>
Date: Tue, 26 Oct 2021 20:29:01 +0100
Subject: Fix: Knife measurements broken when a cut point is in space

Knife angle measurements were mis-aligned if a cut point was in space.
Specifically, the arc drawing would not match with the cut line.

Fixed by removing a correction for kcd->prev.cage.
This correction was originally added for panning with measurements to work.
In hindsight it is not needed and only introduces issues like this.
---
 source/blender/editors/mesh/editmesh_knife.c | 42 ++++++++--------------------
 1 file changed, 12 insertions(+), 30 deletions(-)

(limited to 'source/blender/editors')

diff --git a/source/blender/editors/mesh/editmesh_knife.c b/source/blender/editors/mesh/editmesh_knife.c
index d073f5f2ba4..826a9ce2b6b 100644
--- a/source/blender/editors/mesh/editmesh_knife.c
+++ b/source/blender/editors/mesh/editmesh_knife.c
@@ -184,8 +184,6 @@ typedef struct KnifeMeasureData {
   float cage[3];
   float mval[2];
   bool is_stored;
-  float corr_prev_cage[3]; /* "knife_start_cut" updates prev.cage breaking angle calculations,
-                            * store correct version. */
 } KnifeMeasureData;
 
 typedef struct KnifeUndoFrame {
@@ -496,7 +494,7 @@ static void knifetool_draw_visible_distances(const KnifeTool_OpData *kcd)
   const int distance_precision = 4;
 
   /* Calculate distance and convert to string. */
-  const float cut_len = len_v3v3(kcd->mdata.corr_prev_cage, kcd->curr.cage);
+  const float cut_len = len_v3v3(kcd->prev.cage, kcd->curr.cage);
 
   UnitSettings *unit = &kcd->scene->unit;
   if (unit->system == USER_UNIT_NONE) {
@@ -703,7 +701,7 @@ static void knifetool_draw_visible_angles(const KnifeTool_OpData *kcd)
       else {
         tempkfv = tempkfe->v2;
       }
-      angle = angle_v3v3v3(kcd->mdata.corr_prev_cage, kcd->curr.cage, tempkfv->cageco);
+      angle = angle_v3v3v3(kcd->prev.cage, kcd->curr.cage, tempkfv->cageco);
       if (angle < min_angle) {
         min_angle = angle;
         kfe = tempkfe;
@@ -717,7 +715,7 @@ static void knifetool_draw_visible_angles(const KnifeTool_OpData *kcd)
       ED_view3d_project_float_global(kcd->region, end, end_ss, V3D_PROJ_TEST_NOP);
 
       knifetool_draw_angle(kcd,
-                           kcd->mdata.corr_prev_cage,
+                           kcd->prev.cage,
                            kcd->curr.cage,
                            end,
                            kcd->prev.mval,
@@ -730,11 +728,11 @@ static void knifetool_draw_visible_angles(const KnifeTool_OpData *kcd)
     kfe = kcd->curr.edge;
 
     /* Check for most recent cut (if cage is part of previous cut). */
-    if (!compare_v3v3(kfe->v1->cageco, kcd->mdata.corr_prev_cage, KNIFE_FLT_EPSBIG) &&
-        !compare_v3v3(kfe->v2->cageco, kcd->mdata.corr_prev_cage, KNIFE_FLT_EPSBIG)) {
+    if (!compare_v3v3(kfe->v1->cageco, kcd->prev.cage, KNIFE_FLT_EPSBIG) &&
+        !compare_v3v3(kfe->v2->cageco, kcd->prev.cage, KNIFE_FLT_EPSBIG)) {
       /* Determine acute angle. */
-      float angle1 = angle_v3v3v3(kcd->mdata.corr_prev_cage, kcd->curr.cage, kfe->v1->cageco);
-      float angle2 = angle_v3v3v3(kcd->mdata.corr_prev_cage, kcd->curr.cage, kfe->v2->cageco);
+      float angle1 = angle_v3v3v3(kcd->prev.cage, kcd->curr.cage, kfe->v1->cageco);
+      float angle2 = angle_v3v3v3(kcd->prev.cage, kcd->curr.cage, kfe->v2->cageco);
 
       float angle;
       float *end;
@@ -751,14 +749,8 @@ static void knifetool_draw_visible_angles(const KnifeTool_OpData *kcd)
       float end_ss[2];
       ED_view3d_project_float_global(kcd->region, end, end_ss, V3D_PROJ_TEST_NOP);
 
-      knifetool_draw_angle(kcd,
-                           kcd->mdata.corr_prev_cage,
-                           kcd->curr.cage,
-                           end,
-                           kcd->prev.mval,
-                           kcd->curr.mval,
-                           end_ss,
-                           angle);
+      knifetool_draw_angle(
+          kcd, kcd->prev.cage, kcd->curr.cage, end, kcd->prev.mval, kcd->curr.mval, end_ss, angle);
     }
   }
 
@@ -852,10 +844,10 @@ static void knifetool_draw_visible_angles(const KnifeTool_OpData *kcd)
         kcd, kcd->curr.cage, kcd->prev.cage, end, kcd->curr.mval, kcd->prev.mval, end_ss, angle);
   }
   else if (kcd->mdata.is_stored && !kcd->prev.is_space) {
-    float angle = angle_v3v3v3(kcd->curr.cage, kcd->mdata.corr_prev_cage, kcd->mdata.cage);
+    float angle = angle_v3v3v3(kcd->curr.cage, kcd->prev.cage, kcd->mdata.cage);
     knifetool_draw_angle(kcd,
                          kcd->curr.cage,
-                         kcd->mdata.corr_prev_cage,
+                         kcd->prev.cage,
                          kcd->mdata.cage,
                          kcd->curr.mval,
                          kcd->prev.mval,
@@ -2396,7 +2388,7 @@ static void knife_add_cut(KnifeTool_OpData *kcd)
   }
 
   /* Save values for angle drawing calculations. */
-  copy_v3_v3(kcd->mdata.cage, kcd->mdata.corr_prev_cage);
+  copy_v3_v3(kcd->mdata.cage, kcd->prev.cage);
   copy_v2_v2(kcd->mdata.mval, kcd->prev.mval);
   kcd->mdata.is_stored = true;
 
@@ -4525,16 +4517,6 @@ static int knifetool_modal(bContext *C, wmOperator *op, const wmEvent *event)
             kcd->init = kcd->curr;
           }
 
-          /* Preserve correct prev.cage for angle drawing calculations. */
-          if (kcd->prev.edge == NULL && kcd->prev.vert == NULL) {
-            /* "knife_start_cut" moves prev.cage so needs to be recalculated. */
-            /* Only occurs if prev was started on a face. */
-            knifetool_recast_cageco(kcd, kcd->prev.mval, kcd->mdata.corr_prev_cage);
-          }
-          else {
-            copy_v3_v3(kcd->mdata.corr_prev_cage, kcd->prev.cage);
-          }
-
           /* Freehand drawing is incompatible with cut-through. */
           if (kcd->cut_through == false) {
             kcd->is_drag_hold = true;
-- 
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