/// <summary>
/// This is called by the "ConvexHull" class.
/// </summary>
/// <typeparam name="TVertex"></typeparam>
/// <typeparam name="TFace"></typeparam>
/// <param name="data"></param>
/// <returns></returns>
internal static Tuple <IEnumerable <TVertex>, IEnumerable <TFace> > GetConvexHullAndFaces <TVertex, TFace>(IEnumerable <IVertexPosition> data)
where TFace : ConvexFace <TVertex, TFace>, new()
where TVertex : IVertexPosition
{
ConvexHullInternal ch = new ConvexHullInternal(data);
return(Tuple.Create(
ch.GetConvexHullInternal <TVertex>(),
ch.GetConvexFacesInternal <TVertex, TFace>()));
}
/// <summary>
/// This is called by the "ConvexHull" class.
/// </summary>
/// <typeparam name="TVertex"></typeparam>
/// <typeparam name="TFace"></typeparam>
/// <param name="data"></param>
/// <returns></returns>
internal static void GetConvexHullAndFaces <TVertex, TFace>(IEnumerable <IVertex> data, out IEnumerable <TVertex> points, out IEnumerable <TFace> faces)
where TFace : ConvexFace <TVertex, TFace>, new()
where TVertex : IVertex
{
ConvexHullInternal ch = new ConvexHullInternal(data);
points = ch.GetConvexHullInternal <TVertex>();
faces = ch.GetConvexFacesInternal <TVertex, TFace>();
// return Tuple.Create(
// ch.GetConvexHullInternal<TVertex>(),
// ch.GetConvexFacesInternal<TVertex, TFace>());
}
/// <summary>
/// Creates the Delaunay triangulation of the input data.
/// Be careful with concurrency, because during the computation, the vertex position arrays get resized.
/// </summary>
/// <param name="data"></param>
/// <returns></returns>
public static DelaunayTriangulation <TVertex, TCell> Create(IEnumerable <TVertex> data)
{
if (data == null)
{
throw new ArgumentException("data can't be null.");
}
if (!(data is IList <TVertex>))
{
data = data.ToArray();
}
if (data.Count() == 0)
{
return new DelaunayTriangulation <TVertex, TCell> {
Cells = Enumerable.Empty <TCell>()
}
}
;
int dimension = data.First().Position.Length;
// Resize the arrays and lift the data.
foreach (var p in data)
{
double lenSq = StarMath.norm2(p.Position, dimension, true);
var v = p.Position;
Array.Resize(ref v, dimension + 1);
p.Position = v;
p.Position[dimension] = lenSq;
}
// Find the convex hull
var delaunayFaces = ConvexHullInternal.GetConvexFacesInternal <TVertex, TCell>(data);
// Resize the data back
foreach (var p in data)
{
var v = p.Position;
Array.Resize(ref v, dimension);
p.Position = v;
}
// Remove the "upper" faces
for (var i = delaunayFaces.Count - 1; i >= 0; i--)
{
var candidate = delaunayFaces[i];
if (candidate.Normal[dimension] >= 0)
{
for (int fi = 0; fi < candidate.AdjacentFaces.Length; fi++)
{
var f = candidate.AdjacentFaces[fi];
if (f != null)
{
for (int j = 0; j < f.AdjacentFaces.Length; j++)
{
if (object.ReferenceEquals(f.AdjacentFaces[j], candidate))
{
f.AdjacentFaces[j] = null;
}
}
}
}
var li = delaunayFaces.Count - 1;
delaunayFaces[i] = delaunayFaces[li];
delaunayFaces.RemoveAt(li);
}
}
// Create the "TCell" representation.
int cellCount = delaunayFaces.Count;
var cells = new TCell[cellCount];
for (int i = 0; i < cellCount; i++)
{
var face = delaunayFaces[i];
var vertices = new TVertex[dimension + 1];
for (int j = 0; j <= dimension; j++)
{
vertices[j] = (TVertex)face.Vertices[j].Vertex;
}
cells[i] = new TCell
{
Vertices = vertices,
Adjacency = new TCell[dimension + 1]
};
face.Tag = i;
}
for (int i = 0; i < cellCount; i++)
{
var face = delaunayFaces[i];
var cell = cells[i];
for (int j = 0; j <= dimension; j++)
{
if (face.AdjacentFaces[j] == null)
{
continue;
}
cell.Adjacency[j] = cells[face.AdjacentFaces[j].Tag];
}
}
return(new DelaunayTriangulation <TVertex, TCell> {
Cells = cells
});
}
