private static void EdgeEvent(DTSweepContext tcx, PolygonPoint ep, PolygonPoint eq,
DelaunayTriangle triangle, PolygonPoint point)
{
PolygonPoint p1, p2;
if (IsEdgeSideOfTriangle(triangle, ep, eq))
{
return;
}
p1 = triangle.PointCCWFrom(point);
Orientation o1 = TriangulationUtil.Orient2D(eq, p1, ep);
if (o1 == Orientation.Collinear)
{
// TODO: Split edge in two
//// splitEdge( ep, eq, p1 );
// edgeEvent( tcx, p1, eq, triangle, point );
// edgeEvent( tcx, ep, p1, triangle, p1 );
// return;
throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet", eq, p1, ep);
}
p2 = triangle.PointCWFrom(point);
Orientation o2 = TriangulationUtil.Orient2D(eq, p2, ep);
if (o2 == Orientation.Collinear)
{
// TODO: Split edge in two
// edgeEvent( tcx, p2, eq, triangle, point );
// edgeEvent( tcx, ep, p2, triangle, p2 );
// return;
throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet", eq, p2, ep);
}
if (o1 == o2)
{
// Need to decide if we are rotating CW or CCW to get to a triangle
// that will cross edge
if (o1 == Orientation.CW)
{
triangle = triangle.NeighborCCWFrom(point);
}
else
{
triangle = triangle.NeighborCWFrom(point);
}
EdgeEvent(tcx, ep, eq, triangle, point);
}
else
{
// This triangle crosses constraint so lets flippin start!
FlipEdgeEvent(tcx, ep, eq, triangle, point);
}
}
private static void FlipEdgeEvent(DTSweepContext tcx, PolygonPoint ep, PolygonPoint eq,
DelaunayTriangle t, PolygonPoint p)
{
DelaunayTriangle ot = t.NeighborAcrossFrom(p);
PolygonPoint 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 InvalidOperationException("[BUG:FIXME] FLIP failed due to missing triangle");
}
bool inScanArea = TriangulationUtil.InScanArea(p, t.PointCCWFrom(p), t.PointCWFrom(p), op);
if (inScanArea)
{
// 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.EdgeEvent.ConstrainedEdge.Q &&
ep == tcx.EdgeEvent.ConstrainedEdge.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 = TriangulationUtil.Orient2D(eq, op, ep);
t = NextFlipTriangle(tcx, o, t, ot, p, op);
FlipEdgeEvent(tcx, ep, eq, t, p);
}
}
else
{
PolygonPoint newP = NextFlipPoint(ep, eq, ot, op);
FlipScanEdgeEvent(tcx, ep, eq, t, ot, newP);
EdgeEvent(tcx, ep, eq, t, p);
}
}
/// <summary>
/// Try to map a node to all sides of this triangle that don't have
/// a neighbor.
/// </summary>
public void MapTriangleToNodes(DelaunayTriangle t)
{
for (int i = 0; i < 3; i++)
{
if (t.Neighbors[i] == null)
{
AdvancingFrontNode n = Front.LocatePoint(t.PointCWFrom(t.Points[i]));
if (n != null)
{
n.Triangle = t;
}
}
}
}
/// <summary>
/// When we need to traverse from one triangle to the next we need
/// the point in current triangle that is the opposite point to the next
/// triangle.
/// </summary>
private static PolygonPoint NextFlipPoint(PolygonPoint ep, PolygonPoint eq,
DelaunayTriangle ot, PolygonPoint op)
{
Orientation o2d = TriangulationUtil.Orient2D(eq, op, ep);
switch (o2d)
{
case Orientation.CW:
return(ot.PointCCWFrom(op));
case Orientation.CCW:
return(ot.PointCWFrom(op));
case Orientation.Collinear:
// TODO: implement support for point on constraint edge
throw new PointOnEdgeException("Point on constrained edge not supported yet", eq, op, ep);
default:
throw new NotImplementedException("Orientation not handled");
}
}
/// <summary>
/// Returns true if triangle was legalized
/// </summary>
private static bool Legalize(DTSweepContext tcx, DelaunayTriangle 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++)
{
// TODO: fix so that cEdge is always valid when creating new triangles then we can check it here
// instead of below with ot
if (t.EdgeIsDelaunay[i])
{
continue;
}
DelaunayTriangle ot = t.Neighbors[i];
if (ot == null)
{
continue;
}
PolygonPoint p = t.Points[i];
PolygonPoint op = ot.OppositePoint(t, p);
int oi = ot.IndexOf(op);
// If this is a Constrained Edge or a Delaunay Edge(only during recursive legalization)
// then we should not try to legalize
if (ot.EdgeIsConstrained[oi] || ot.EdgeIsDelaunay[oi])
{
t.EdgeIsConstrained[i] = ot.EdgeIsConstrained[oi];
// XXX: have no good way of setting this property when creating new triangles so lets set it here
continue;
}
if (!TriangulationUtil.SmartIncircle(p, t.PointCCWFrom(p), t.PointCWFrom(p), op))
{
continue;
}
// Lets mark this shared edge as Delaunay
t.EdgeIsDelaunay[i] = true;
ot.EdgeIsDelaunay[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
if (!Legalize(tcx, t))
{
tcx.MapTriangleToNodes(t);
}
if (!Legalize(tcx, ot))
{
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.EdgeIsDelaunay[i] = false;
ot.EdgeIsDelaunay[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);
}
/// <summary>
/// Scan part of the FlipScan algorithm<br>
/// When a triangle pair isn't flippable we will scan for the next
/// point that is inside the flip triangle scan area. When found
/// we generate a new flipEdgeEvent
/// </summary>
/// <param name="tcx"></param>
/// <param name="ep">last point on the edge we are traversing</param>
/// <param name="eq">first point on the edge we are traversing</param>
/// <param name="flipTriangle">the current triangle sharing the point eq with edge</param>
/// <param name="t"></param>
/// <param name="p"></param>
private static void FlipScanEdgeEvent(DTSweepContext tcx, PolygonPoint ep, PolygonPoint eq,
DelaunayTriangle flipTriangle, DelaunayTriangle t, PolygonPoint p)
{
DelaunayTriangle ot;
PolygonPoint op, newP;
bool inScanArea;
ot = t.NeighborAcrossFrom(p);
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 Exception("[BUG:FIXME] FLIP failed due to missing triangle");
}
inScanArea = TriangulationUtil.InScanArea(eq, flipTriangle.PointCCWFrom(eq), flipTriangle.PointCWFrom(eq),
op);
if (inScanArea)
{
// 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 flipTriangle first
// Turns out at first glance that this is somewhat complicated
// so it will have to wait.
}
else
{
newP = NextFlipPoint(ep, eq, ot, op);
FlipScanEdgeEvent(tcx, ep, eq, flipTriangle, ot, newP);
}
}
/// <param name="t">Opposite triangle</param>
/// <param name="p">The point in t that isn't shared between the triangles</param>
public PolygonPoint OppositePoint(DelaunayTriangle t, PolygonPoint p)
{
Debug.Assert(t != this, "self-pointer error");
return(PointCWFrom(t.PointCWFrom(p)));
}