/// <param name="t">Opposite triangle</param>
/// <param name="p">The point in t that isn't shared between the triangles</param>
public TriangulationPoint OppositePoint( DelaunayTriangle t, TriangulationPoint p )
{
Debug.Assert( t != this, "self-pointer error" );
return PointCW( t.PointCW( p ) );
}
public void MarkEdge( DelaunayTriangle triangle )
{
for( int i = 0; i < 3; i++ )
if( edgeIsConstrained[i] )
{
triangle.MarkConstrainedEdge( points[( i + 1 ) % 3], points[( i + 2 ) % 3] );
}
}
/// <summary>
/// Exhaustive search to update neighbor pointers
/// </summary>
public void MarkNeighbor( DelaunayTriangle t )
{
if( t.Contains( points[1], points[2] ) )
{
neighbors[0] = t;
t.MarkNeighbor( points[1], points[2], this );
}
else if( t.Contains( points[0], points[2] ) )
{
neighbors[1] = t;
t.MarkNeighbor( points[0], points[2], this );
}
else if( t.Contains( points[0], points[1] ) )
{
neighbors[2] = t;
t.MarkNeighbor( points[0], points[1], this );
}
else
{
Debug.WriteLine( "markNeighbor failed" );
}
}
public void ClearNeighbor( DelaunayTriangle triangle )
{
if( neighbors[0] == triangle )
{
neighbors[0] = null;
}
else if( neighbors[1] == triangle )
{
neighbors[1] = null;
}
else
{
neighbors[2] = null;
}
}
public void AddTriangle( DelaunayTriangle t )
{
_triangles.Add( t );
}
/// <summary>
/// Update neighbor pointers
/// </summary>
/// <param name="p1">Point 1 of the shared edge</param>
/// <param name="p2">Point 2 of the shared edge</param>
/// <param name="t">This triangle's new neighbor</param>
private void MarkNeighbor( TriangulationPoint p1, TriangulationPoint p2, DelaunayTriangle t )
{
if( ( p1 == points[2] && p2 == points[1] ) || ( p1 == points[1] && p2 == points[2] ) )
{
neighbors[0] = t;
}
else if( ( p1 == points[0] && p2 == points[2] ) || ( p1 == points[2] && p2 == points[0] ) )
{
neighbors[1] = t;
}
else if( ( p1 == points[0] && p2 == points[1] ) || ( p1 == points[1] && p2 == points[0] ) )
{
neighbors[2] = t;
}
else
{
Debug.WriteLine( "Neighbor error, please report!" );
// throw new Exception("Neighbor error, please report!");
}
}
/// <summary>
/// oppposite point
/// </summary>
/// <param name="t">Opposite triangle</param>
/// <param name="p">The point in t that isn't shared between the triangles</param>
public TriangulationPoint OppositePoint(DelaunayTriangle t, TriangulationPoint p)
{
Debug.Assert(t != this, "self-pointer error");
return(PointCW(t.PointCW(p)));
}
/// <summary>
/// Rotates a triangle pair one vertex CW
/// n2 n2
/// P +-----+ P +-----+
/// | t /| |\ t |
/// | / | | \ |
/// n1| / |n3 n1| \ |n3
/// | / | after CW | \ |
/// |/ oT | | oT \|
/// +-----+ oP +-----+
/// n4 n4
/// </summary>
private static void RotateTrianglePair(DelaunayTriangle t, PolygonPoint p, DelaunayTriangle ot,
PolygonPoint op)
{
DelaunayTriangle n1, n2, n3, n4;
n1 = t.NeighborCCWFrom(p);
n2 = t.NeighborCWFrom(p);
n3 = ot.NeighborCCWFrom(op);
n4 = ot.NeighborCWFrom(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 dEdge
ot.SetDelaunayEdgeCCW(p, de1);
t.SetDelaunayEdgeCW(p, de2);
t.SetDelaunayEdgeCCW(op, de3);
ot.SetDelaunayEdgeCW(op, de4);
// Remap cEdge
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.Neighbors.Clear();
ot.Neighbors.Clear();
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);
}
/// <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>
/// After a flip we have two triangles and know that only one will still be
/// intersecting the edge. So decide which to contiune with and legalize the other
/// </summary>
/// <param name="tcx"></param>
/// <param name="o">should be the result of an TriangulationUtil.orient2d( eq, op, ep )</param>
/// <param name="t">triangle 1</param>
/// <param name="ot">triangle 2</param>
/// <param name="p">a point shared by both triangles</param>
/// <param name="op">another point shared by both triangles</param>
/// <returns>returns the triangle still intersecting the edge</returns>
private static DelaunayTriangle NextFlipTriangle(DTSweepContext tcx, Orientation o, DelaunayTriangle t,
DelaunayTriangle ot, PolygonPoint p,
PolygonPoint op)
{
int edgeIndex;
if (o == Orientation.CCW)
{
// ot is not crossing edge after flip
edgeIndex = ot.EdgeIndex(p, op);
ot.EdgeIsDelaunay[edgeIndex] = true;
Legalize(tcx, ot);
ot.EdgeIsDelaunay.Clear();
return(t);
}
// t is not crossing edge after flip
edgeIndex = t.EdgeIndex(p, op);
t.EdgeIsDelaunay[edgeIndex] = true;
Legalize(tcx, t);
t.EdgeIsDelaunay.Clear();
return(ot);
}
/// <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)));
}
