/// <summary>
/// Generate a set of mesh faces that represent a delaunay triangulation in the XY plane of the
/// specified set of vertices.
/// Based on the algorithm described here: http://paulbourke.net/papers/triangulate/
/// </summary>
/// <param name="vertices">The vertices to mesh between</param>
/// <param name="faces">Optional. The face collection to which to add the triangles.
/// If null or ommitted, a new MeshFaceCollection will be created.</param>
/// <param name="bounds">The bounding box that contains the triangulation. Should encompass all vertices
/// and, for later voronoi generation, any bounding geometry. If null, the bounding box of the vertices
/// themselves will be used.</param>
/// <param name="clean">Clean up construction Super Triangle. If true, any remaining fragments of the
/// initial generating supertriangle will be removed from the output face list. Set this to false
/// if planning on using this mesh for subsequent voronoi generation so that the edge cells can be extended.</param>
/// <param name="outerVerts">Optional. If input and non-null, this collection will be populated with the exterior vertices - those connected
/// to the original supertriangle. If 'clean' is false, this will instead return the supertriangle vertices.</param>
public static MeshFaceCollection DelaunayTriangulationXY(VertexCollection vertices,
MeshFaceCollection faces = null, BoundingBox bounds = null, bool clean = true, VertexCollection outerVerts = null)
{
List <Vertex> vertexList = vertices.ToList();
vertexList.Sort();
if (faces == null)
{
faces = new MeshFaceCollection();
}
if (bounds == null)
{
bounds = new BoundingBox(vertexList);
}
else
{
bounds = new BoundingBox(bounds);
}
bounds.Scale(5); //Provide a little wriggle room!
// Meshing starts with one 'super triangle' that encloses all vertices.
// This will be removed at the end
MeshFace superTriangle = DelaunayTriangle.GenerateSuperTriangleXY(bounds);
faces.Add(superTriangle);
// Include each vertex in the meshing one at a time
foreach (Vertex v in vertexList)
{
//for (int k = 0; k < 8; k++)
//{
// Vertex v = vertexList[k];
// if (k == 7)
// {
// bool bum = true;
// }
IList <MeshEdge> edges = new List <MeshEdge>(); //The edges of replaced triangles
for (int i = faces.Count - 1; i >= 0; i--)
{
MeshFace face = faces[i];
if (face.XYCircumcircleContainmentQuickCheck(v)) //The vertex lies within the circumcircle of this face
{
//The edges of the triangle are added to the current edge set...
for (int j = 0; j < face.Count; j++)
{
edges.Add(face.GetEdge(j));
}
//...and the triangle is removed.
faces.RemoveAt(i);
}
}
//Remove duplicate edges to retain only the convex hull of edges.
//edges.RemoveDuplicates();
//Replaced with bespoke version
for (int i = edges.Count - 2; i >= 0; i--)
{
MeshEdge itemA = edges[i];
for (int j = edges.Count - 1; j > i; j--)
{
if (itemA.Equals(edges[j]))
{
edges.RemoveAt(j);
edges.RemoveAt(i);
j--;
continue;
}
}
}
// Add triangle fan between all remaining edges and the new vertex
foreach (MeshEdge edge in edges)
{
faces.Add(new DelaunayTriangle(edge, v));
}
}
// Extract outer vertices
if (outerVerts != null)
{
if (clean)
{
var outerFaces = faces.AllWithVertices(new VertexCollection(superTriangle));
foreach (Vertex v in outerFaces.ExtractVertices())
{
outerVerts.Add(v);
}
}
else
{
foreach (Vertex v in superTriangle)
{
outerVerts.Add(v);
}
}
}
// Remove the super triangle and any triangles still attached to it
if (clean)
{
faces.RemoveAllWithVertices(new VertexCollection(superTriangle));
}
return(faces);
}
public bool Equals(ref MeshEdge other)
{
return((Start == other.Start && End == other.End) || (Start == other.End && End == other.Start));
}
