Use poly2tri for triangulation. This fixes some cases where polyPartition couldn't triangulate successfully. Reported as issue #9 in polyPartition repository. Tested with MotorHalter_0.stl cut at 1.2

xs/src/poly2tri/sweep/sweep.cc

@@ -0,0 +1,808 @@
+/*
+ * Poly2Tri Copyright (c) 2009-2010, Poly2Tri Contributors
+ * http://code.google.com/p/poly2tri/
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ * * Neither the name of Poly2Tri nor the names of its contributors may be
+ *   used to endorse or promote products derived from this software without specific
+ *   prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include <stdexcept>
+#include "sweep.h"
+#include "sweep_context.h"
+#include "advancing_front.h"
+#include "../common/utils.h"
+
+namespace p2t {
+
+// Triangulate simple polygon with holes
+void Sweep::Triangulate(SweepContext& tcx)
+{
+  tcx.InitTriangulation();
+  tcx.CreateAdvancingFront(nodes_);
+  // Sweep points; build mesh
+  SweepPoints(tcx);
+  // Clean up
+  FinalizationPolygon(tcx);
+}
+
+void Sweep::SweepPoints(SweepContext& tcx)
+{
+  for (size_t i = 1; i < tcx.point_count(); i++) {
+    Point& point = *tcx.GetPoint(i);
+    Node* node = &PointEvent(tcx, point);
+    for (unsigned int i = 0; i < point.edge_list.size(); i++) {
+      EdgeEvent(tcx, point.edge_list[i], node);
+    }
+  }
+}
+
+void Sweep::FinalizationPolygon(SweepContext& tcx)
+{
+  // Get an Internal triangle to start with
+  Triangle* t = tcx.front()->head()->next->triangle;
+  Point* p = tcx.front()->head()->next->point;
+  while (!t->GetConstrainedEdgeCW(*p)) {
+    t = t->NeighborCCW(*p);
+  }
+
+  // Collect interior triangles constrained by edges
+  tcx.MeshClean(*t);
+}
+
+Node& Sweep::PointEvent(SweepContext& tcx, Point& point)
+{
+  Node& node = tcx.LocateNode(point);
+  Node& new_node = NewFrontTriangle(tcx, point, node);
+
+  // Only need to check +epsilon since point never have smaller
+  // x value than node due to how we fetch nodes from the front
+  if (point.x <= node.point->x + EPSILON) {
+    Fill(tcx, node);
+  }
+
+  //tcx.AddNode(new_node);
+
+  FillAdvancingFront(tcx, new_node);
+  return new_node;
+}
+
+void Sweep::EdgeEvent(SweepContext& tcx, Edge* edge, Node* node)
+{
+  tcx.edge_event.constrained_edge = edge;
+  tcx.edge_event.right = (edge->p->x > edge->q->x);
+
+  if (IsEdgeSideOfTriangle(*node->triangle, *edge->p, *edge->q)) {
+    return;
+  }
+
+  // For now we will do all needed filling
+  // TODO: integrate with flip process might give some better performance
+  //       but for now this avoid the issue with cases that needs both flips and fills
+  FillEdgeEvent(tcx, edge, node);
+  EdgeEvent(tcx, *edge->p, *edge->q, node->triangle, *edge->q);
+}
+
+void Sweep::EdgeEvent(SweepContext& tcx, Point& ep, Point& eq, Triangle* triangle, Point& point)
+{
+  if (IsEdgeSideOfTriangle(*triangle, ep, eq)) {
+    return;
+  }
+
+  Point* p1 = triangle->PointCCW(point);
+  Orientation o1 = Orient2d(eq, *p1, ep);
+  if (o1 == COLLINEAR) {
+    if( triangle->Contains(&eq, p1)) {
+      triangle->MarkConstrainedEdge(&eq, p1 );
+      // We are modifying the constraint maybe it would be better to
+      // not change the given constraint and just keep a variable for the new constraint
+      tcx.edge_event.constrained_edge->q = p1;
+      triangle = &triangle->NeighborAcross(point);
+      EdgeEvent( tcx, ep, *p1, triangle, *p1 );
+    } else {
+      std::runtime_error("EdgeEvent - collinear points not supported");
+      assert(0);
+    }
+    return;
+  }
+
+  Point* p2 = triangle->PointCW(point);
+  Orientation o2 = Orient2d(eq, *p2, ep);
+  if (o2 == COLLINEAR) {
+    if( triangle->Contains(&eq, p2)) {
+      triangle->MarkConstrainedEdge(&eq, p2 );
+      // We are modifying the constraint maybe it would be better to
+      // not change the given constraint and just keep a variable for the new constraint
+      tcx.edge_event.constrained_edge->q = p2;
+      triangle = &triangle->NeighborAcross(point);
+      EdgeEvent( tcx, ep, *p2, triangle, *p2 );
+    } else {
+      std::runtime_error("EdgeEvent - collinear points not supported");
+      assert(0);
+    }
+    return;
+  }
+
+  if (o1 == o2) {
+    // Need to decide if we are rotating CW or CCW to get to a triangle
+    // that will cross edge
+    if (o1 == CW) {
+      triangle = triangle->NeighborCCW(point);
+    }       else{
+      triangle = triangle->NeighborCW(point);
+    }
+    EdgeEvent(tcx, ep, eq, triangle, point);
+  } else {
+    // This triangle crosses constraint so lets flippin start!
+    FlipEdgeEvent(tcx, ep, eq, triangle, point);
+  }
+}
+
+bool Sweep::IsEdgeSideOfTriangle(Triangle& triangle, Point& ep, Point& eq)
+{
+  const int index = triangle.EdgeIndex(&ep, &eq);
+
+  if (index != -1) {
+    triangle.MarkConstrainedEdge(index);
+    Triangle* t = triangle.GetNeighbor(index);
+    if (t) {
+      t->MarkConstrainedEdge(&ep, &eq);
+    }
+    return true;
+  }
+  return false;
+}
+
+Node& Sweep::NewFrontTriangle(SweepContext& tcx, Point& point, Node& node)
+{
+  Triangle* triangle = new Triangle(point, *node.point, *node.next->point);
+
+  triangle->MarkNeighbor(*node.triangle);
+  tcx.AddToMap(triangle);
+
+  Node* new_node = new Node(point);
+  nodes_.push_back(new_node);
+
+  new_node->next = node.next;
+  new_node->prev = &node;
+  node.next->prev = new_node;
+  node.next = new_node;
+
+  if (!Legalize(tcx, *triangle)) {
+    tcx.MapTriangleToNodes(*triangle);
+  }
+
+  return *new_node;
+}
+
+void Sweep::Fill(SweepContext& tcx, Node& node)
+{
+  Triangle* triangle = new Triangle(*node.prev->point, *node.point, *node.next->point);
+
+  // TODO: should copy the constrained_edge value from neighbor triangles
+  //       for now constrained_edge values are copied during the legalize
+  triangle->MarkNeighbor(*node.prev->triangle);
+  triangle->MarkNeighbor(*node.triangle);
+
+  tcx.AddToMap(triangle);
+
+  // Update the advancing front
+  node.prev->next = node.next;
+  node.next->prev = node.prev;
+
+  // If it was legalized the triangle has already been mapped
+  if (!Legalize(tcx, *triangle)) {
+    tcx.MapTriangleToNodes(*triangle);
+  }
+
+}
+
+void Sweep::FillAdvancingFront(SweepContext& tcx, Node& n)
+{
+
+  // Fill right holes
+  Node* node = n.next;
+
+  while (node->next) {
+    // if HoleAngle exceeds 90 degrees then break.
+    if (LargeHole_DontFill(node)) break;
+    Fill(tcx, *node);
+    node = node->next;
+  }
+
+  // Fill left holes
+  node = n.prev;
+
+  while (node->prev) {
+    // if HoleAngle exceeds 90 degrees then break.
+    if (LargeHole_DontFill(node)) break;
+    Fill(tcx, *node);
+    node = node->prev;
+  }
+
+  // Fill right basins
+  if (n.next && n.next->next) {
+    const double angle = BasinAngle(n);
+    if (angle < PI_3div4) {
+      FillBasin(tcx, n);
+    }
+  }
+}
+
+// True if HoleAngle exceeds 90 degrees.
+bool Sweep::LargeHole_DontFill(const Node* node) const {
+
+  const Node* nextNode = node->next;
+  const Node* prevNode = node->prev;
+  if (!AngleExceeds90Degrees(node->point, nextNode->point, prevNode->point))
+          return false;
+
+  // Check additional points on front.
+  const Node* next2Node = nextNode->next;
+  // "..Plus.." because only want angles on same side as point being added.
+  if ((next2Node != NULL) && !AngleExceedsPlus90DegreesOrIsNegative(node->point, next2Node->point, prevNode->point))
+          return false;
+
+  const Node* prev2Node = prevNode->prev;
+  // "..Plus.." because only want angles on same side as point being added.
+  if ((prev2Node != NULL) && !AngleExceedsPlus90DegreesOrIsNegative(node->point, nextNode->point, prev2Node->point))
+          return false;
+
+  return true;
+}
+
+bool Sweep::AngleExceeds90Degrees(const Point* origin, const Point* pa, const Point* pb) const {
+  const double angle = Angle(origin, pa, pb);
+  return ((angle > PI_div2) || (angle < -PI_div2));
+}
+
+bool Sweep::AngleExceedsPlus90DegreesOrIsNegative(const Point* origin, const Point* pa, const Point* pb) const {
+  const double angle = Angle(origin, pa, pb);
+  return (angle > PI_div2) || (angle < 0);
+}
+
+double Sweep::Angle(const Point* origin, const Point* pa, const Point* pb) const {
+  /* 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
+   */
+  const double px = origin->x;
+  const double py = origin->y;
+  const double ax = pa->x- px;
+  const double ay = pa->y - py;
+  const double bx = pb->x - px;
+  const double by = pb->y - py;
+  const double x = ax * by - ay * bx;
+  const double y = ax * bx + ay * by;
+  return atan2(x, y);
+}
+
+double Sweep::BasinAngle(const Node& node) const
+{
+  const double ax = node.point->x - node.next->next->point->x;
+  const double ay = node.point->y - node.next->next->point->y;
+  return atan2(ay, ax);
+}
+
+double Sweep::HoleAngle(const Node& node) const
+{
+  /* 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
+   */
+  const double ax = node.next->point->x - node.point->x;
+  const double ay = node.next->point->y - node.point->y;
+  const double bx = node.prev->point->x - node.point->x;
+  const double by = node.prev->point->y - node.point->y;
+  return atan2(ax * by - ay * bx, ax * bx + ay * by);
+}
+
+bool Sweep::Legalize(SweepContext& tcx, Triangle& t)
+{
+  // To legalize a triangle we start by finding if any of the three edges
+  // violate the Delaunay condition
+  for (int i = 0; i < 3; i++) {
+    if (t.delaunay_edge[i])
+      continue;
+
+    Triangle* ot = t.GetNeighbor(i);
+
+    if (ot) {
+      Point* p = t.GetPoint(i);
+      Point* op = ot->OppositePoint(t, *p);
+      int oi = ot->Index(op);
+
+      // If this is a Constrained Edge or a Delaunay Edge(only during recursive legalization)
+      // then we should not try to legalize
+      if (ot->constrained_edge[oi] || ot->delaunay_edge[oi]) {
+        t.constrained_edge[i] = ot->constrained_edge[oi];
+        continue;
+      }
+
+      bool inside = Incircle(*p, *t.PointCCW(*p), *t.PointCW(*p), *op);
+
+      if (inside) {
+        // Lets mark this shared edge as Delaunay
+        t.delaunay_edge[i] = true;
+        ot->delaunay_edge[oi] = true;
+
+        // Lets rotate shared edge one vertex CW to legalize it
+        RotateTrianglePair(t, *p, *ot, *op);
+
+        // We now got one valid Delaunay Edge shared by two triangles
+        // This gives us 4 new edges to check for Delaunay
+
+        // Make sure that triangle to node mapping is done only one time for a specific triangle
+        bool not_legalized = !Legalize(tcx, t);
+        if (not_legalized) {
+          tcx.MapTriangleToNodes(t);
+        }
+
+        not_legalized = !Legalize(tcx, *ot);
+        if (not_legalized)
+          tcx.MapTriangleToNodes(*ot);
+
+        // Reset the Delaunay edges, since they only are valid Delaunay edges
+        // until we add a new triangle or point.
+        // XXX: need to think about this. Can these edges be tried after we
+        //      return to previous recursive level?
+        t.delaunay_edge[i] = false;
+        ot->delaunay_edge[oi] = false;
+
+        // If triangle have been legalized no need to check the other edges since
+        // the recursive legalization will handles those so we can end here.
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+bool Sweep::Incircle(const Point& pa, const Point& pb, const Point& pc, const Point& pd) const
+{
+  const double adx = pa.x - pd.x;
+  const double ady = pa.y - pd.y;
+  const double bdx = pb.x - pd.x;
+  const double bdy = pb.y - pd.y;
+
+  const double adxbdy = adx * bdy;
+  const double bdxady = bdx * ady;
+  const double oabd = adxbdy - bdxady;
+
+  if (oabd <= 0)
+    return false;
+
+  const double cdx = pc.x - pd.x;
+  const double cdy = pc.y - pd.y;
+
+  const double cdxady = cdx * ady;
+  const double adxcdy = adx * cdy;
+  const double ocad = cdxady - adxcdy;
+
+  if (ocad <= 0)
+    return false;
+
+  const double bdxcdy = bdx * cdy;
+  const double cdxbdy = cdx * bdy;
+
+  const double alift = adx * adx + ady * ady;
+  const double blift = bdx * bdx + bdy * bdy;
+  const double clift = cdx * cdx + cdy * cdy;
+
+  const double det = alift * (bdxcdy - cdxbdy) + blift * ocad + clift * oabd;
+
+  return det > 0;
+}
+
+void Sweep::RotateTrianglePair(Triangle& t, Point& p, Triangle& ot, Point& op) const
+{
+  Triangle* n1, *n2, *n3, *n4;
+  n1 = t.NeighborCCW(p);
+  n2 = t.NeighborCW(p);
+  n3 = ot.NeighborCCW(op);
+  n4 = ot.NeighborCW(op);
+
+  bool ce1, ce2, ce3, ce4;
+  ce1 = t.GetConstrainedEdgeCCW(p);
+  ce2 = t.GetConstrainedEdgeCW(p);
+  ce3 = ot.GetConstrainedEdgeCCW(op);
+  ce4 = ot.GetConstrainedEdgeCW(op);
+
+  bool de1, de2, de3, de4;
+  de1 = t.GetDelunayEdgeCCW(p);
+  de2 = t.GetDelunayEdgeCW(p);
+  de3 = ot.GetDelunayEdgeCCW(op);
+  de4 = ot.GetDelunayEdgeCW(op);
+
+  t.Legalize(p, op);
+  ot.Legalize(op, p);
+
+  // Remap delaunay_edge
+  ot.SetDelunayEdgeCCW(p, de1);
+  t.SetDelunayEdgeCW(p, de2);
+  t.SetDelunayEdgeCCW(op, de3);
+  ot.SetDelunayEdgeCW(op, de4);
+
+  // Remap constrained_edge
+  ot.SetConstrainedEdgeCCW(p, ce1);
+  t.SetConstrainedEdgeCW(p, ce2);
+  t.SetConstrainedEdgeCCW(op, ce3);
+  ot.SetConstrainedEdgeCW(op, ce4);
+
+  // Remap neighbors
+  // XXX: might optimize the markNeighbor by keeping track of
+  //      what side should be assigned to what neighbor after the
+  //      rotation. Now mark neighbor does lots of testing to find
+  //      the right side.
+  t.ClearNeighbors();
+  ot.ClearNeighbors();
+  if (n1) ot.MarkNeighbor(*n1);
+  if (n2) t.MarkNeighbor(*n2);
+  if (n3) t.MarkNeighbor(*n3);
+  if (n4) ot.MarkNeighbor(*n4);
+  t.MarkNeighbor(ot);
+}
+
+void Sweep::FillBasin(SweepContext& tcx, Node& node)
+{
+  if (Orient2d(*node.point, *node.next->point, *node.next->next->point) == CCW) {
+    tcx.basin.left_node = node.next->next;
+  } else {
+    tcx.basin.left_node = node.next;
+  }
+
+  // Find the bottom and right node
+  tcx.basin.bottom_node = tcx.basin.left_node;
+  while (tcx.basin.bottom_node->next
+         && tcx.basin.bottom_node->point->y >= tcx.basin.bottom_node->next->point->y) {
+    tcx.basin.bottom_node = tcx.basin.bottom_node->next;
+  }
+  if (tcx.basin.bottom_node == tcx.basin.left_node) {
+    // No valid basin
+    return;
+  }
+
+  tcx.basin.right_node = tcx.basin.bottom_node;
+  while (tcx.basin.right_node->next
+         && tcx.basin.right_node->point->y < tcx.basin.right_node->next->point->y) {
+    tcx.basin.right_node = tcx.basin.right_node->next;
+  }
+  if (tcx.basin.right_node == tcx.basin.bottom_node) {
+    // No valid basins
+    return;
+  }
+
+  tcx.basin.width = tcx.basin.right_node->point->x - tcx.basin.left_node->point->x;
+  tcx.basin.left_highest = tcx.basin.left_node->point->y > tcx.basin.right_node->point->y;
+
+  FillBasinReq(tcx, tcx.basin.bottom_node);
+}
+
+void Sweep::FillBasinReq(SweepContext& tcx, Node* node)
+{
+  // if shallow stop filling
+  if (IsShallow(tcx, *node)) {
+    return;
+  }
+
+  Fill(tcx, *node);
+
+  if (node->prev == tcx.basin.left_node && node->next == tcx.basin.right_node) {
+    return;
+  } else if (node->prev == tcx.basin.left_node) {
+    Orientation o = Orient2d(*node->point, *node->next->point, *node->next->next->point);
+    if (o == CW) {
+      return;
+    }
+    node = node->next;
+  } else if (node->next == tcx.basin.right_node) {
+    Orientation o = Orient2d(*node->point, *node->prev->point, *node->prev->prev->point);
+    if (o == CCW) {
+      return;
+    }
+    node = node->prev;
+  } else {
+    // Continue with the neighbor node with lowest Y value
+    if (node->prev->point->y < node->next->point->y) {
+      node = node->prev;
+    } else {
+      node = node->next;
+    }
+  }
+
+  FillBasinReq(tcx, node);
+}
+
+bool Sweep::IsShallow(SweepContext& tcx, Node& node)
+{
+  double height;
+
+  if (tcx.basin.left_highest) {
+    height = tcx.basin.left_node->point->y - node.point->y;
+  } else {
+    height = tcx.basin.right_node->point->y - node.point->y;
+  }
+
+  // if shallow stop filling
+  if (tcx.basin.width > height) {
+    return true;
+  }
+  return false;
+}
+
+void Sweep::FillEdgeEvent(SweepContext& tcx, Edge* edge, Node* node)
+{
+  if (tcx.edge_event.right) {
+    FillRightAboveEdgeEvent(tcx, edge, node);
+  } else {
+    FillLeftAboveEdgeEvent(tcx, edge, node);
+  }
+}
+
+void Sweep::FillRightAboveEdgeEvent(SweepContext& tcx, Edge* edge, Node* node)
+{
+  while (node->next->point->x < edge->p->x) {
+    // Check if next node is below the edge
+    if (Orient2d(*edge->q, *node->next->point, *edge->p) == CCW) {
+      FillRightBelowEdgeEvent(tcx, edge, *node);
+    } else {
+      node = node->next;
+    }
+  }
+}
+
+void Sweep::FillRightBelowEdgeEvent(SweepContext& tcx, Edge* edge, Node& node)
+{
+  if (node.point->x < edge->p->x) {
+    if (Orient2d(*node.point, *node.next->point, *node.next->next->point) == CCW) {
+      // Concave
+      FillRightConcaveEdgeEvent(tcx, edge, node);
+    } else{
+      // Convex
+      FillRightConvexEdgeEvent(tcx, edge, node);
+      // Retry this one
+      FillRightBelowEdgeEvent(tcx, edge, node);
+    }
+  }
+}
+
+void Sweep::FillRightConcaveEdgeEvent(SweepContext& tcx, Edge* edge, Node& node)
+{
+  Fill(tcx, *node.next);
+  if (node.next->point != edge->p) {
+    // Next above or below edge?
+    if (Orient2d(*edge->q, *node.next->point, *edge->p) == CCW) {
+      // Below
+      if (Orient2d(*node.point, *node.next->point, *node.next->next->point) == CCW) {
+        // Next is concave
+        FillRightConcaveEdgeEvent(tcx, edge, node);
+      } else {
+        // Next is convex
+      }
+    }
+  }
+
+}
+
+void Sweep::FillRightConvexEdgeEvent(SweepContext& tcx, Edge* edge, Node& node)
+{
+  // Next concave or convex?
+  if (Orient2d(*node.next->point, *node.next->next->point, *node.next->next->next->point) == CCW) {
+    // Concave
+    FillRightConcaveEdgeEvent(tcx, edge, *node.next);
+  } else{
+    // Convex
+    // Next above or below edge?
+    if (Orient2d(*edge->q, *node.next->next->point, *edge->p) == CCW) {
+      // Below
+      FillRightConvexEdgeEvent(tcx, edge, *node.next);
+    } else{
+      // Above
+    }
+  }
+}
+
+void Sweep::FillLeftAboveEdgeEvent(SweepContext& tcx, Edge* edge, Node* node)
+{
+  while (node->prev->point->x > edge->p->x) {
+    // Check if next node is below the edge
+    if (Orient2d(*edge->q, *node->prev->point, *edge->p) == CW) {
+      FillLeftBelowEdgeEvent(tcx, edge, *node);
+    } else {
+      node = node->prev;
+    }
+  }
+}
+
+void Sweep::FillLeftBelowEdgeEvent(SweepContext& tcx, Edge* edge, Node& node)
+{
+  if (node.point->x > edge->p->x) {
+    if (Orient2d(*node.point, *node.prev->point, *node.prev->prev->point) == CW) {
+      // Concave
+      FillLeftConcaveEdgeEvent(tcx, edge, node);
+    } else {
+      // Convex
+      FillLeftConvexEdgeEvent(tcx, edge, node);
+      // Retry this one
+      FillLeftBelowEdgeEvent(tcx, edge, node);
+    }
+  }
+}
+
+void Sweep::FillLeftConvexEdgeEvent(SweepContext& tcx, Edge* edge, Node& node)
+{
+  // Next concave or convex?
+  if (Orient2d(*node.prev->point, *node.prev->prev->point, *node.prev->prev->prev->point) == CW) {
+    // Concave
+    FillLeftConcaveEdgeEvent(tcx, edge, *node.prev);
+  } else{
+    // Convex
+    // Next above or below edge?
+    if (Orient2d(*edge->q, *node.prev->prev->point, *edge->p) == CW) {
+      // Below
+      FillLeftConvexEdgeEvent(tcx, edge, *node.prev);
+    } else{
+      // Above
+    }
+  }
+}
+
+void Sweep::FillLeftConcaveEdgeEvent(SweepContext& tcx, Edge* edge, Node& node)
+{
+  Fill(tcx, *node.prev);
+  if (node.prev->point != edge->p) {
+    // Next above or below edge?
+    if (Orient2d(*edge->q, *node.prev->point, *edge->p) == CW) {
+      // Below
+      if (Orient2d(*node.point, *node.prev->point, *node.prev->prev->point) == CW) {
+        // Next is concave
+        FillLeftConcaveEdgeEvent(tcx, edge, node);
+      } else{
+        // Next is convex
+      }
+    }
+  }
+
+}
+
+void Sweep::FlipEdgeEvent(SweepContext& tcx, Point& ep, Point& eq, Triangle* t, Point& p)
+{
+  Triangle& ot = t->NeighborAcross(p);
+  Point& op = *ot.OppositePoint(*t, p);
+
+  if (&ot == NULL) {
+    // If we want to integrate the fillEdgeEvent do it here
+    // With current implementation we should never get here
+    //throw new RuntimeException( "[BUG:FIXME] FLIP failed due to missing triangle");
+    assert(0);
+  }
+
+  if (InScanArea(p, *t->PointCCW(p), *t->PointCW(p), op)) {
+    // Lets rotate shared edge one vertex CW
+    RotateTrianglePair(*t, p, ot, op);
+    tcx.MapTriangleToNodes(*t);
+    tcx.MapTriangleToNodes(ot);
+
+    if (p == eq && op == ep) {
+      if (eq == *tcx.edge_event.constrained_edge->q && ep == *tcx.edge_event.constrained_edge->p) {
+        t->MarkConstrainedEdge(&ep, &eq);
+        ot.MarkConstrainedEdge(&ep, &eq);
+        Legalize(tcx, *t);
+        Legalize(tcx, ot);
+      } else {
+        // XXX: I think one of the triangles should be legalized here?
+      }
+    } else {
+      Orientation o = Orient2d(eq, op, ep);
+      t = &NextFlipTriangle(tcx, (int)o, *t, ot, p, op);
+      FlipEdgeEvent(tcx, ep, eq, t, p);
+    }
+  } else {
+    Point& newP = NextFlipPoint(ep, eq, ot, op);
+    FlipScanEdgeEvent(tcx, ep, eq, *t, ot, newP);
+    EdgeEvent(tcx, ep, eq, t, p);
+  }
+}
+
+Triangle& Sweep::NextFlipTriangle(SweepContext& tcx, int o, Triangle& t, Triangle& ot, Point& p, Point& op)
+{
+  if (o == CCW) {
+    // ot is not crossing edge after flip
+    int edge_index = ot.EdgeIndex(&p, &op);
+    ot.delaunay_edge[edge_index] = true;
+    Legalize(tcx, ot);
+    ot.ClearDelunayEdges();
+    return t;
+  }
+
+  // t is not crossing edge after flip
+  int edge_index = t.EdgeIndex(&p, &op);
+
+  t.delaunay_edge[edge_index] = true;
+  Legalize(tcx, t);
+  t.ClearDelunayEdges();
+  return ot;
+}
+
+Point& Sweep::NextFlipPoint(Point& ep, Point& eq, Triangle& ot, Point& op)
+{
+  Orientation o2d = Orient2d(eq, op, ep);
+  if (o2d == CW) {
+    // Right
+    return *ot.PointCCW(op);
+  } else if (o2d == CCW) {
+    // Left
+    return *ot.PointCW(op);
+  }
+  throw std::runtime_error("[Unsupported] Opposing point on constrained edge");
+}
+
+void Sweep::FlipScanEdgeEvent(SweepContext& tcx, Point& ep, Point& eq, Triangle& flip_triangle,
+                              Triangle& t, Point& p)
+{
+  Triangle& ot = t.NeighborAcross(p);
+  Point& op = *ot.OppositePoint(t, p);
+
+  if (&t.NeighborAcross(p) == NULL) {
+    // If we want to integrate the fillEdgeEvent do it here
+    // With current implementation we should never get here
+    //throw new RuntimeException( "[BUG:FIXME] FLIP failed due to missing triangle");
+    assert(0);
+  }
+
+  if (InScanArea(eq, *flip_triangle.PointCCW(eq), *flip_triangle.PointCW(eq), op)) {
+    // flip with new edge op->eq
+    FlipEdgeEvent(tcx, eq, op, &ot, op);
+    // TODO: Actually I just figured out that it should be possible to
+    //       improve this by getting the next ot and op before the the above
+    //       flip and continue the flipScanEdgeEvent here
+    // set new ot and op here and loop back to inScanArea test
+    // also need to set a new flip_triangle first
+    // Turns out at first glance that this is somewhat complicated
+    // so it will have to wait.
+  } else{
+    Point& newP = NextFlipPoint(ep, eq, ot, op);
+    FlipScanEdgeEvent(tcx, ep, eq, flip_triangle, ot, newP);
+  }
+}
+
+Sweep::~Sweep() {
+
+    // Clean up memory
+    for(size_t i = 0; i < nodes_.size(); i++) {
+        delete nodes_[i];
+    }
+
+}
+
+}
+