private static void FlipEdgeEvent(DTSweepContext tcx, TriangulationPoint ep, TriangulationPoint eq, DelaunayTriangle t, TriangulationPoint p)
{
DelaunayTriangle ot = t.NeighborAcrossFrom(p);
TriangulationPoint 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");
}
if (tcx.IsDebugEnabled)
{
tcx.DTDebugContext.PrimaryTriangle = t;
tcx.DTDebugContext.SecondaryTriangle = ot;
} // TODO: remove
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)
{
if (tcx.IsDebugEnabled)
{
Console.WriteLine("[FLIP] - constrained edge done"); // TODO: remove
}
t.MarkConstrainedEdge(ep, eq);
ot.MarkConstrainedEdge(ep, eq);
Legalize(tcx, t);
Legalize(tcx, ot);
}
else
{
if (tcx.IsDebugEnabled)
{
Console.WriteLine("[FLIP] - subedge done"); // TODO: remove
}
// XXX: I think one of the triangles should be legalized here?
}
}
else
{
if (tcx.IsDebugEnabled)
{
Console.WriteLine("[FLIP] - flipping and continuing with triangle still crossing edge"); // TODO: remove
}
Orientation o = TriangulationUtil.Orient2d(eq, op, ep);
t = NextFlipTriangle(tcx, o, t, ot, p, op);
FlipEdgeEvent(tcx, ep, eq, t, p);
}
}
else
{
TriangulationPoint newP = null;
if (NextFlipPoint(ep, eq, ot, op, out newP))
{
FlipScanEdgeEvent(tcx, ep, eq, t, ot, newP);
EdgeEvent(tcx, ep, eq, t, p);
}
}
}
/// <summary>
/// If this is a Delaunay Triangulation of a pointset we need to fill so the triangle mesh gets a ConvexHull
/// </summary>
private static void FinalizationConvexHull(DTSweepContext tcx)
{
AdvancingFrontNode n1, n2;
DelaunayTriangle t1, t2;
TriangulationPoint first, p1;
n1 = tcx.Front.Head.Next;
n2 = n1.Next;
first = n1.Point;
TurnAdvancingFrontConvex(tcx, n1, n2);
// Lets remove triangles connected to the two "algorithm" points
// XXX: When the first three nodes are points in a triangle we need to do a flip before
// removing triangles or we will lose a valid triangle.
// Same for last three nodes!
// !!! If I implement ConvexHull for lower right and left boundary this fix should not be
// needed and the removed triangles will be added again by default
n1 = tcx.Front.Tail.Prev;
if (n1.Triangle.Contains(n1.Next.Point) && n1.Triangle.Contains(n1.Prev.Point))
{
t1 = n1.Triangle.NeighborAcrossFrom(n1.Point);
RotateTrianglePair(n1.Triangle, n1.Point, t1, t1.OppositePoint(n1.Triangle, n1.Point));
tcx.MapTriangleToNodes(n1.Triangle);
tcx.MapTriangleToNodes(t1);
}
n1 = tcx.Front.Head.Next;
if (n1.Triangle.Contains(n1.Prev.Point) && n1.Triangle.Contains(n1.Next.Point))
{
t1 = n1.Triangle.NeighborAcrossFrom(n1.Point);
RotateTrianglePair(n1.Triangle, n1.Point, t1, t1.OppositePoint(n1.Triangle, n1.Point));
tcx.MapTriangleToNodes(n1.Triangle);
tcx.MapTriangleToNodes(t1);
}
// Lower right boundary
first = tcx.Front.Head.Point;
n2 = tcx.Front.Tail.Prev;
t1 = n2.Triangle;
p1 = n2.Point;
n2.Triangle = null;
do
{
tcx.RemoveFromList(t1);
p1 = t1.PointCCWFrom(p1);
if (p1 == first)
{
break;
}
t2 = t1.NeighborCCWFrom(p1);
t1.Clear();
t1 = t2;
} while (true);
// Lower left boundary
first = tcx.Front.Head.Next.Point;
p1 = t1.PointCWFrom(tcx.Front.Head.Point);
t2 = t1.NeighborCWFrom(tcx.Front.Head.Point);
t1.Clear();
t1 = t2;
while (p1 != first)
{
tcx.RemoveFromList(t1);
p1 = t1.PointCCWFrom(p1);
t2 = t1.NeighborCCWFrom(p1);
t1.Clear();
t1 = t2;
}
// Remove current head and tail node now that we have removed all triangles attached
// to them. Then set new head and tail node points
tcx.Front.Head = tcx.Front.Head.Next;
tcx.Front.Head.Prev = null;
tcx.Front.Tail = tcx.Front.Tail.Prev;
tcx.Front.Tail.Next = null;
}
private static void EdgeEvent(DTSweepContext tcx, TriangulationPoint ep, TriangulationPoint eq, DelaunayTriangle triangle, TriangulationPoint point)
{
TriangulationPoint p1, p2;
if (tcx.IsDebugEnabled)
{
tcx.DTDebugContext.PrimaryTriangle = triangle;
}
if (IsEdgeSideOfTriangle(triangle, ep, eq))
{
return;
}
p1 = triangle.PointCCWFrom(point);
Orientation o1 = TriangulationUtil.Orient2d(eq, p1, ep);
if (o1 == Orientation.Collinear)
{
if (triangle.Contains(eq) && triangle.Contains(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.NeighborAcrossFrom(point);
EdgeEvent(tcx, ep, p1, triangle, p1);
}
else
{
throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet", ep, eq, p1);
}
if (tcx.IsDebugEnabled)
{
Console.WriteLine("EdgeEvent - Point on constrained edge");
}
return;
}
p2 = triangle.PointCWFrom(point);
Orientation o2 = TriangulationUtil.Orient2d(eq, p2, ep);
if (o2 == Orientation.Collinear)
{
if (triangle.Contains(eq) && triangle.Contains(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.NeighborAcrossFrom(point);
EdgeEvent(tcx, ep, p2, triangle, p2);
}
else
{
throw new PointOnEdgeException("EdgeEvent - Point on constrained edge not supported yet", ep, eq, p2);
}
if (tcx.IsDebugEnabled)
{
Console.WriteLine("EdgeEvent - Point on constrained edge");
}
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 == 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);
}
}
/// <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;
}
TriangulationPoint p = t.Points[i];
TriangulationPoint 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.SetConstrainedEdgeAcross(p, 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);
}
