From: Barak Itkin <lightningismyname@gmail.com>
Date: Sun, 3 Jun 2012 19:36:03 +0000 (+0300)
Subject: Add changes according to commit acf81f1f1764 in poly2tri (C++)
X-Git-Tag: p2tc-0.1.0~38
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=17860d49cb4f29f7919230a97e6c8af4f8a4e829;p=poly2tri-c

Add changes according to commit acf81f1f1764 in poly2tri (C++)
---

diff --git a/poly2tri-c/p2t/sweep/sweep.c b/poly2tri-c/p2t/sweep/sweep.c
index 2c08af9..7680075 100644
--- a/poly2tri-c/p2t/sweep/sweep.c
+++ b/poly2tri-c/p2t/sweep/sweep.c
@@ -310,8 +310,8 @@ p2t_sweep_fill_advancingfront (P2tSweep *THIS, P2tSweepContext *tcx, P2tNode* n)
 
   while (node->next)
     {
-      double angle = p2t_sweep_hole_angle (THIS, node);
-      if (angle > G_PI_2 || angle < -G_PI_2) break;
+      /* if HoleAngle exceeds 90 degrees then break. */
+      if (p2t_sweep_large_hole_dont_fill (THIS, node)) break;
       p2t_sweep_fill (THIS, tcx, node);
       node = node->next;
     }
@@ -321,8 +321,8 @@ p2t_sweep_fill_advancingfront (P2tSweep *THIS, P2tSweepContext *tcx, P2tNode* n)
 
   while (node->prev)
     {
-      double angle = p2t_sweep_hole_angle (THIS, node);
-      if (angle > G_PI_2 || angle < -G_PI_2) break;
+      /* if HoleAngle exceeds 90 degrees then break. */
+      if (p2t_sweep_large_hole_dont_fill (THIS, node)) break;
       p2t_sweep_fill (THIS, tcx, node);
       node = node->prev;
     }
@@ -338,6 +338,68 @@ p2t_sweep_fill_advancingfront (P2tSweep *THIS, P2tSweepContext *tcx, P2tNode* n)
     }
 }
 
+/* True if HoleAngle exceeds 90 degrees. */
+gboolean
+p2t_sweep_large_hole_dont_fill (P2tSweep *THIS, P2tNode* node)
+{
+  P2tNode* nextNode = node->next;
+  P2tNode* prevNode = node->prev;
+  P2tNode *next2Node, *prev2Node;
+  if (! p2t_sweep_angle_exceeds_90_degrees (THIS, node->point, nextNode->point, prevNode->point))
+    return FALSE;
+
+  /* Check additional points on front. */
+  next2Node = nextNode->next;
+  /* "..Plus.." because only want angles on same side as point being added. */
+  if ((next2Node != NULL) && !p2t_sweep_angle_exceeds_plus_90_degrees_or_is_negative (THIS, node->point, next2Node->point, prevNode->point))
+    return FALSE;
+
+  prev2Node = prevNode->prev;
+  /* "..Plus.." because only want angles on same side as point being added. */
+  if ((prev2Node != NULL) && !p2t_sweep_angle_exceeds_plus_90_degrees_or_is_negative (THIS, node->point, nextNode->point, prev2Node->point))
+    return FALSE;
+
+  return TRUE;
+}
+
+gboolean
+p2t_sweep_angle_exceeds_90_degrees(P2tSweep* THIS, P2tPoint* origin, P2tPoint* pa, P2tPoint* pb)
+{
+  gdouble angle = p2t_sweep_angle (THIS, origin, pa, pb);
+  gboolean exceeds90Degrees = ((angle > G_PI_2) || (angle < -G_PI_2));
+  return exceeds90Degrees;
+}
+
+gboolean
+p2t_sweep_angle_exceeds_plus_90_degrees_or_is_negative (P2tSweep* THIS, P2tPoint* origin, P2tPoint* pa, P2tPoint* pb)
+{
+  gdouble angle = p2t_sweep_angle (THIS, origin, pa, pb);
+  gboolean exceedsPlus90DegreesOrIsNegative = (angle > G_PI_2) || (angle < 0);
+  return exceedsPlus90DegreesOrIsNegative;
+}
+
+gdouble
+p2t_sweep_angle (P2tSweep* THIS, P2tPoint* origin, P2tPoint* pa, P2tPoint* pb) {
+  /* Complex plane
+   * ab = cosA +i*sinA
+   * ab = (ax + ay*i)(bx + by*i) = (ax*bx + ay*by) + i(ax*by-ay*bx)
+   * atan2(y,x) computes the principal value of the argument function
+   * applied to the complex number x+iy
+   * Where x = ax*bx + ay*by
+   *       y = ax*by - ay*bx
+   */
+  double px = origin->x;
+  double py = origin->y;
+  double ax = pa->x - px;
+  double ay = pa->y - py;
+  double bx = pb->x - px;
+  double by = pb->y - py;
+  double x = ax * by - ay * bx;
+  double y = ax * bx + ay * by;
+  double angle = atan2(x, y);
+  return angle;
+}
+
 double
 p2t_sweep_basin_angle (P2tSweep *THIS, P2tNode* node)
 {
diff --git a/poly2tri-c/p2t/sweep/sweep.h b/poly2tri-c/p2t/sweep/sweep.h
index e030c9c..7105fc4 100644
--- a/poly2tri-c/p2t/sweep/sweep.h
+++ b/poly2tri-c/p2t/sweep/sweep.h
@@ -172,6 +172,13 @@ void p2t_sweep_rotate_triangle_pair (P2tSweep *THIS, P2tTriangle *t, P2tPoint* p
  */
 void p2t_sweep_fill_advancingfront (P2tSweep *THIS, P2tSweepContext *tcx, P2tNode* n);
 
+/* Decision-making about when to Fill hole.
+ * Contributed by ToolmakerSteve2 */
+gboolean p2t_sweep_large_hole_dont_fill (P2tSweep* THIS, P2tNode* node);
+gboolean p2t_sweep_angle_exceeds_90_degrees (P2tSweep* THIS, P2tPoint* origin, P2tPoint* pa, P2tPoint* pb);
+gboolean p2t_sweep_angle_exceeds_plus_90_degrees_or_is_negative (P2tSweep* THIS, P2tPoint* origin, P2tPoint* pa, P2tPoint* pb);
+gdouble  p2t_sweep_angle (P2tSweep* THIS, P2tPoint* origin, P2tPoint* pa, P2tPoint* pb);
+
 /**
  *
  * @param node - middle node