/// <summary>
/// Triangulates the shape.
/// </summary>
/// <returns>The output list.</returns>
public List<float[]> Triangulate(float[] offset, float scale = 1.0f)
{
var output = new List<float[]>();
Points.Reverse();
var context = new SweepContext();
context.AddPoints(Points);
// Hole edges
foreach (Shape h in Holes)
context.AddHole(h.Points);
context.InitTriangulation();
var sweep = new Sweep();
sweep.Triangulate(context);
var triangles = context.GetTriangles();
foreach (Triangle tri in triangles)
{
//tri.ReversePointFlow();
output.Add(((float[])tri.Points[0]).VectorScale(scale).Add(offset));
output.Add(((float[])tri.Points[2]).VectorScale(scale).Add(offset));
output.Add(((float[])tri.Points[1]).VectorScale(scale).Add(offset));
}
return output;
}
private void FillEdgeEvent(SweepContext tcx, Edge edge, Node node)
{
if (tcx.EdgeEvent.Right)
{
FillRightAboveEdgeEvent(tcx, edge, node);
}
else
{
FillLeftAboveEdgeEvent(tcx, edge, node);
}
}
public void Triangulate(SweepContext tcx)
{
_nodes = new List <Node>();
tcx.InitTriangulation();
tcx.CreateAdvancingFront(_nodes);
// Sweep points; build mesh
SweepPoints(tcx);
// Clean up
FinalizationPolygon(tcx);
}
private void FinalizationPolygon(SweepContext tcx)
{
// Get an Internal triangle to start with
Triangle t = tcx.Front._head.Next.Triangle;
TriPoint p = tcx.Front._head.Next.Point;
while (!t.GetConstrainedEdgeCW(p))
{
t = t.NeighborCCW(p);
}
tcx.MeshClean(t);
}
private void FillBasinReq(SweepContext tcx, Node node)
{
// if shallow stop filling
if (IsShallow(tcx, node))
{
return;
}
Fill(tcx, node);
if (node.Prev == tcx.Basin.LeftNode && node.Next == tcx.Basin.RightNode)
{
return;
}
else if (node.Prev == tcx.Basin.LeftNode)
{
Winding o = TriUtil.Orient2d(node.Point, node.Next.Point, node.Next.Next.Point);
if (o == Winding.CW)
{
return;
}
node = node.Next;
}
else if (node.Next == tcx.Basin.RightNode)
{
Winding o = TriUtil.Orient2d(node.Point, node.Prev.Point, node.Prev.Prev.Point);
if (o == Winding.CCW)
{
return;
}
node = node.Prev;
}
else
{
// Continue with the neighbor node with lowest Y value
if (node.Prev.Point.Y < node.Next.Point.Y)
{
node = node.Prev;
}
else
{
node = node.Next;
}
}
FillBasinReq(tcx, node);
}
private void FillLeftAboveEdgeEvent(SweepContext tcx, Edge edge, Node node)
{
while (node.Prev.Point.X > edge.P.X)
{
// Check if next node is below the edge
if (TriUtil.Orient2d(edge.Q, node.Prev.Point, edge.P) == Winding.CW)
{
FillLeftBelowEdgeEvent(tcx, edge, node);
}
else
{
node = node.Prev;
}
}
}
private void SweepPoints(SweepContext tcx)
{
for (int i = 1; i < tcx.PointCount(); i++)
{
TriPoint point = tcx.GetPoint(i);
Node node = PointEvent(tcx, point);
if (point.EdgeList != null)
{
for (int j = 0; j < point.EdgeList.Count; j++)
{
EdgeEvent(tcx, point.EdgeList[j], node);
}
}
}
}
private void EdgeEvent(SweepContext tcx, Edge edge, Node node)
{
tcx.EdgeEvent.ConstrainedEdge = edge;
tcx.EdgeEvent.Right = (edge.P.X > edge.Q.X);
if (IsEdgeSideOfTriangle(node.Triangle, edge.P, edge.Q))
{
return;
}
// For now we will do all needed filling
// TODO: integrate with flip process might give some better performance
// but for now this avoid the issue with cases that needs both flips and fills
FillEdgeEvent(tcx, edge, node);
EdgeEvent(tcx, edge.P, edge.Q, node.Triangle, edge.Q);
}
private Node PointEvent(SweepContext tcx, TriPoint point)
{
Node node = tcx.LocateNode(point);
Node new_node = NewFrontTriangle(tcx, point, node);
// Only need to check +epsilon since point never have smaller
// x value than node due to how we fetch nodes from the front
if (point.X <= node.Point.X + TriUtil.EPSILON)
{
Fill(tcx, node);
}
//tcx.AddNode(new_node);
FillAdvancingFront(tcx, new_node);
return(new_node);
}
private void FillLeftBelowEdgeEvent(SweepContext tcx, Edge edge, Node node)
{
if (node.Point.X > edge.P.X)
{
if (TriUtil.Orient2d(node.Point, node.Prev.Point, node.Prev.Prev.Point) == Winding.CW)
{
// Concave
FillLeftConcaveEdgeEvent(tcx, edge, node);
}
else
{
// Convex
FillLeftConvexEdgeEvent(tcx, edge, node);
// Retry this one
FillLeftBelowEdgeEvent(tcx, edge, node);
}
}
}
/// <summary>
/// Triangulates the shape.
/// </summary>
/// <returns>The output list.</returns>
public List<Triangle> Triangulate()
{
var context = new SweepContext();
var distinctPoints = Points.Distinct().ToList();
context.AddPoints(distinctPoints);
foreach (var hole in Holes)
context.AddHole(hole.Points);
context.InitTriangulation();
var sweep = new Sweep();
sweep.Triangulate(context);
return context.GetTriangles();
}
private void Fill(SweepContext tcx, Node node)
{
Triangle triangle = new Triangle(node.Prev.Point, node.Point, node.Next.Point);
triangle.MarkNeighbor(node.Prev.Triangle);
triangle.MarkNeighbor(node.Triangle);
tcx.AddToMap(triangle);
// Update the advancing front
node.Prev.Next = node.Next;
node.Next.Prev = node.Prev;
// If it was legalized the triangle has already been mapped
if (!Legalize(tcx, triangle))
{
tcx.MapTriangleToNodes(triangle);
}
}
private void FillBasin(SweepContext tcx, Node node)
{
if (TriUtil.Orient2d(node.Point, node.Next.Point, node.Next.Next.Point) == Winding.CCW)
{
tcx.Basin.LeftNode = node.Next.Next;
}
else
{
tcx.Basin.LeftNode = node.Next;
}
// Find the bottom and right node
tcx.Basin.BottomNode = tcx.Basin.LeftNode;
while (tcx.Basin.BottomNode.Next != null &&
tcx.Basin.BottomNode.Point.Y >= tcx.Basin.BottomNode.Next.Point.Y)
{
tcx.Basin.BottomNode = tcx.Basin.BottomNode.Next;
}
if (tcx.Basin.BottomNode == tcx.Basin.LeftNode)
{
// No valid basin
return;
}
tcx.Basin.RightNode = tcx.Basin.BottomNode;
while (tcx.Basin.RightNode.Next != null &&
tcx.Basin.RightNode.Point.Y < tcx.Basin.RightNode.Next.Point.Y)
{
tcx.Basin.RightNode = tcx.Basin.RightNode.Next;
}
if (tcx.Basin.RightNode == tcx.Basin.BottomNode)
{
// No valid basins
return;
}
tcx.Basin.Width = tcx.Basin.RightNode.Point.X - tcx.Basin.LeftNode.Point.X;
tcx.Basin.LeftHighest = tcx.Basin.LeftNode.Point.Y > tcx.Basin.RightNode.Point.Y;
FillBasinReq(tcx, tcx.Basin.BottomNode);
}
private void FillLeftConcaveEdgeEvent(SweepContext tcx, Edge edge, Node node)
{
Fill(tcx, node.Prev);
if (node.Prev.Point != edge.P)
{
// Next above or below edge?
if (TriUtil.Orient2d(edge.Q, node.Prev.Point, edge.P) == Winding.CW)
{
// Below
if (TriUtil.Orient2d(node.Point, node.Prev.Point, node.Prev.Prev.Point) == Winding.CW)
{
// Next is concave
FillLeftConcaveEdgeEvent(tcx, edge, node);
}
else
{
// Next is convex
}
}
}
}
private bool IsShallow(SweepContext tcx, Node node)
{
double height;
if (tcx.Basin.LeftHighest)
{
height = tcx.Basin.LeftNode.Point.Y - node.Point.Y;
}
else
{
height = tcx.Basin.RightNode.Point.Y - node.Point.Y;
}
// if shallow stop filling
if (tcx.Basin.Width > height)
{
return(true);
}
return(false);
}
private void FlipEdgeEvent(SweepContext tcx, TriPoint ep, TriPoint eq, Triangle t, TriPoint p)
{
Triangle ot = t.NeighborAcross(p);
TriPoint op = ot.OppositePoint(t, p);
if (TriUtil.InScanArea(p, t.PointCCW(p), t.PointCW(p), op))
{
// 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
{
Winding o = TriUtil.Orient2d(eq, op, ep);
t = NextFlipTriangle(tcx, o, t, ot, p, op);
FlipEdgeEvent(tcx, ep, eq, t, p);
}
}
else
{
TriPoint newP = NextFlipPoint(ep, eq, ot, op);
FlipScanEdgeEvent(tcx, ep, eq, t, ot, newP);
EdgeEvent(tcx, ep, eq, t, p);
}
}
private void FillAdvancingFront(SweepContext tcx, Node n)
{
// Fill right holes
Node node = n.Next;
while (node.Next != null)
{
// if HoleAngle exceeds 90 degrees then break.
if (LargeHole_DontFill(node))
{
break;
}
Fill(tcx, node);
node = node.Next;
}
// Fill left holes
node = n.Prev;
while (node.Prev != null)
{
// if HoleAngle exceeds 90 degrees then break.
if (LargeHole_DontFill(node))
{
break;
}
Fill(tcx, node);
node = node.Prev;
}
// Fill right basins
if (n.Next != null && n.Next.Next != null)
{
double angle = BasinAngle(n);
if (angle < TriUtil.PI_3div4)
{
FillBasin(tcx, n);
}
}
}
private Triangle NextFlipTriangle(SweepContext tcx, Winding o, Triangle t, Triangle ot, TriPoint p, TriPoint op)
{
int edge_index;
if (o == Winding.CCW)
{
// ot is not crossing edge after flip
edge_index = ot.EdgeIndex(p, op);
ot.DelaunayEdge[edge_index] = true;
Legalize(tcx, ot);
ot.ClearDelaunayEdges();
return(t);
}
// t is not crossing edge after flip
edge_index = t.EdgeIndex(p, op);
t.DelaunayEdge[edge_index] = true;
Legalize(tcx, t);
t.ClearDelaunayEdges();
return(ot);
}
private Node NewFrontTriangle(SweepContext tcx, TriPoint point, Node node)
{
Triangle triangle = new Triangle(point, node.Point, node.Next.Point);
triangle.MarkNeighbor(node.Triangle);
tcx.AddToMap(triangle);
Node new_node = new Node(point);
_nodes.Add(new_node);
new_node.Next = node.Next;
new_node.Prev = node;
node.Next.Prev = new_node;
node.Next = new_node;
if (!Legalize(tcx, triangle))
{
tcx.MapTriangleToNodes(triangle);
}
return(new_node);
}
private void FillRightConvexEdgeEvent(SweepContext tcx, Edge edge, Node node)
{
// Next concave or convex?
if (TriUtil.Orient2d(node.Next.Point, node.Next.Next.Point, node.Next.Next.Next.Point) == Winding.CCW)
{
// Concave
FillRightConcaveEdgeEvent(tcx, edge, node.Next);
}
else
{
// Convex
// Next above or below edge?
if (TriUtil.Orient2d(edge.Q, node.Next.Next.Point, edge.P) == Winding.CCW)
{
// Below
FillRightConvexEdgeEvent(tcx, edge, node.Next);
}
else
{
// Above
}
}
}
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 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);
}
}
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);
}
