private void EdgeEvent(SweepContext tcx, TriPoint ep, TriPoint eq, Triangle triangle, TriPoint point)
{
if (IsEdgeSideOfTriangle(triangle, ep, eq))
{
return;
}
TriPoint p1 = triangle.PointCCW(point);
Winding o1 = TriUtil.Orient2d(eq, p1, ep);
if (o1 == Winding.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.EdgeEvent.ConstrainedEdge.Q = p1;
triangle = triangle.NeighborAcross(point);
EdgeEvent(tcx, ep, p1, triangle, p1);
}
else
{
throw new NotSupportedException("EdgeEvent - collinear points not supported");
}
return;
}
TriPoint p2 = triangle.PointCW(point);
Winding o2 = TriUtil.Orient2d(eq, p2, ep);
if (o2 == Winding.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.EdgeEvent.ConstrainedEdge.Q = p2;
triangle = triangle.NeighborAcross(point);
EdgeEvent(tcx, ep, p2, triangle, p2);
}
else
{
throw new NotSupportedException("EdgeEvent - collinear points not supported");
}
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 == Winding.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);
}
}
/**
* Rotates a triangle pair one vertex CW
*<pre>
* n2 n2
* P +-----+ P +-----+
* | t /| |\ t |
* | / | | \ |
* n1| / |n3 n1| \ |n3
* | / | after CW | \ |
* |/ oT | | oT \|
* +-----+ oP +-----+
* n4 n4
* </pre>
*/
private void RotateTrianglePair(Triangle t, TriPoint p, Triangle ot, TriPoint op)
{
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.GetDelaunayEdgeCCW(p);
de2 = t.GetDelaunayEdgeCW(p);
de3 = ot.GetDelaunayEdgeCCW(op);
de4 = ot.GetDelaunayEdgeCW(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 != null)
{
ot.MarkNeighbor(n1);
}
if (n2 != null)
{
t.MarkNeighbor(n2);
}
if (n3 != null)
{
t.MarkNeighbor(n3);
}
if (n4 != null)
{
ot.MarkNeighbor(n4);
}
t.MarkNeighbor(ot);
}
private void FlipScanEdgeEvent(SweepContext tcx, TriPoint ep, TriPoint eq, Triangle flip_triangle, Triangle t, TriPoint p)
{
Triangle ot = t.NeighborAcross(p);
TriPoint op = ot.OppositePoint(t, p);
if (TriUtil.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
{
TriPoint newP = NextFlipPoint(ep, eq, ot, op);
FlipScanEdgeEvent(tcx, ep, eq, flip_triangle, ot, newP);
}
}
private bool 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.DelaunayEdge[i])
{
continue;
}
Triangle ot = t.GetNeighbor(i);
if (ot != null)
{
TriPoint p = t.Points[i];
TriPoint 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.ConstrainedEdge[oi] || ot.DelaunayEdge[oi])
{
t.ConstrainedEdge[i] = ot.ConstrainedEdge[oi];
continue;
}
bool inside = Incircle(p, t.PointCCW(p), t.PointCW(p), op);
if (inside)
{
// Lets mark this shared edge as Delaunay
t.DelaunayEdge[i] = true;
ot.DelaunayEdge[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.DelaunayEdge[i] = false;
ot.DelaunayEdge[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);
}
