Class ConformingDelaunayTriangulator

Computes a Conforming Delaunay Triangulation over a set of sites and a set of linear constraints.

Inheritance

object

ConformingDelaunayTriangulator

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: NetTopologySuite.Triangulate

Assembly: NetTopologySuite.dll

Syntax

public class ConformingDelaunayTriangulator

Remarks

A conforming Delaunay triangulation is a true Delaunay triangulation. In it each constraint segment is present as a union of one or more triangulation edges. Constraint segments may be subdivided into two or more triangulation edges by the insertion of additional sites. The additional sites are called Steiner points, and are necessary to allow the segments to be faithfully reflected in the triangulation while maintaining the Delaunay property. Another way of stating this is that in a conforming Delaunay triangulation every constraint segment will be the union of a subset of the triangulation edges (up to tolerance).

A Conforming Delaunay triangulation is distinct from a Constrained Delaunay triangulation. A Constrained Delaunay triangulation is not necessarily fully Delaunay, and it contains the constraint segments exactly as edges of the triangulation.

A typical usage pattern for the triangulator is:

ConformingDelaunayTriangulator cdt = new ConformingDelaunayTriangulator(sites, tolerance);
// optional
cdt.SplitPointFinder = splitPointFinder;
cdt.VertexFactory = vertexFactory;
cdt.SetConstraints(segments,  new List<Vertex>(vertexMap.Values));
cdt.FormInitialDelaunay();
cdt.EnforceConstraints();
subdiv = cdt.Subdivision;

Constructors

ConformingDelaunayTriangulator(IEnumerable<Vertex>, double)

Creates a Conforming Delaunay Triangulation based on the given unconstrained initial vertices. The initial vertex set should not contain any vertices which appear in the constraint set.

Declaration

public ConformingDelaunayTriangulator(IEnumerable<Vertex> initialVertices, double tolerance)

Parameters

Type	Name	Description
IEnumerable<Vertex>	initialVertices	a collection of ConstraintVertex
double	tolerance	the distance tolerance below which points are considered identical

Properties

ConstraintSegments

Gets the Segments which represent the constraints.

Declaration

public ICollection<Segment> ConstraintSegments { get; }

Property Value

Type	Description
ICollection<Segment>

ConvexHull

Gets the convex hull of all the sites in the triangulation, including constraint vertices. Only valid after the constraints have been enforced.

Declaration

public Geometry ConvexHull { get; }

Property Value

Type	Description
Geometry

Remarks

the convex hull of the sites

InitialVertices

Gets the sites (vertices) used to initialize the triangulation.

Declaration

public IList<Vertex> InitialVertices { get; }

Property Value

Type	Description
IList<Vertex>

KDT

Gets the KdTree<T> which contains the vertices of the triangulation.

Declaration

public KdTree<Vertex> KDT { get; }

Property Value

Type	Description
KdTree<Vertex>

SplitPointFinder

Gets or sets the IConstraintSplitPointFinder to be used during constraint enforcement. Different splitting strategies may be appropriate for special situations.

Declaration

public IConstraintSplitPointFinder SplitPointFinder { get; set; }

Property Value

Type	Description
IConstraintSplitPointFinder

Remarks

the ConstraintSplitPointFinder to be used

Subdivision

Gets the QuadEdgeSubdivision which represents the triangulation.

Declaration

public QuadEdgeSubdivision Subdivision { get; }

Property Value

Type	Description
QuadEdgeSubdivision

Tolerance

Gets the tolerance value used to construct the triangulation.

Declaration

public double Tolerance { get; }

Property Value

Type	Description
double

Remarks

a tolerance value

VertexFactory

Gets and sets the ConstraintVertexFactory used to create new constraint vertices at split points.

Declaration

public ConstraintVertexFactory VertexFactory { get; set; }

Property Value

Type	Description
ConstraintVertexFactory

Remarks

Allows the setting of a custom ConstraintVertexFactory to be used to allow vertices carrying extra information to be created.

Methods

EnforceConstraints()

Enforces the supplied constraints into the triangulation.

Declaration

public void EnforceConstraints()

Exceptions

Type	Condition
ConstraintEnforcementException	if the constraints cannot be enforced

FormInitialDelaunay()

Computes the Delaunay triangulation of the initial sites.

Declaration

public void FormInitialDelaunay()

InsertSite(Coordinate)

Inserts a site into the triangulation, maintaining the conformal Delaunay property. This can be used to further refine the triangulation if required (e.g. to approximate the medial axis of the constraints, or to improve the grading of the triangulation).

Declaration

public void InsertSite(Coordinate p)

Parameters

Type	Name	Description
Coordinate	p	the location of the site to insert

SetConstraints(IList<Segment>, IList<Vertex>)

Sets the constraints to be conformed to by the computed triangulation. The constraints must not contain duplicate segments (up to orientation). The unique set of vertices (as ConstraintVertexes) forming the constraints must also be supplied. Supplying it explicitly allows the ConstraintVertexes to be initialized appropriately (e.g. with external data), and avoids re-computing the unique set if it is already available.

Declaration

public void SetConstraints(IList<Segment> segments, IList<Vertex> segVertices)

Parameters

Type	Name	Description
IList<Segment>	segments	list of the constraint Segments
IList<Vertex>	segVertices	the set of unique ConstraintVertexes referenced by the segments