C++ Triangle::PointCW方法代码示例

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;
}

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);
  }
}

void SweepContext::MapTriangleToNodes(Triangle& t)
{
  for (int i = 0; i < 3; i++) {
    if (!t.GetNeighbor(i)) {
      Node* n = front_->LocatePoint(t.PointCW(*t.GetPoint(i)));
      if (n)
        n->triangle = &t;
    }
  }
}