Class Tri

A memory-efficient representation of a triangle in a triangulation. Contains three vertices, and links to adjacent Tris for each edge. Tris are constructed independently, and if needed linked into a triangulation using TriangulationBuilder.

An edge of a Tri in a triangulation is called a boundary edge if it has no adjacent triangle.
The set of Tris containing boundary edges are called the triangulation border.

Inheritance

object

Tri

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: NetTopologySuite.Triangulate.Tri

Assembly: NetTopologySuite.dll

Syntax

public class Tri

Constructors

Tri(Coordinate, Coordinate, Coordinate)

Creates a triangle with the given vertices. The vertices should be oriented clockwise.

Declaration

public Tri(Coordinate p0, Coordinate p1, Coordinate p2)

Parameters

Type	Name	Description
Coordinate	p0	The first triangle vertex
Coordinate	p1	The second triangle vertex
Coordinate	p2	The third triangle vertex

Properties

Area

Gets the area of the triangle.

Declaration

public double Area { get; }

Property Value

Type	Description
double	The area of the triangle

Length

Gets the perimeter length of the perimeter of the triangle.

Declaration

public double Length { get; }

Property Value

Type	Description
double

NumAdjacent

Computes the number of triangle adjacent to this triangle. This is a number in the range [0,2].

Declaration

public int NumAdjacent { get; }

Property Value

Type	Description
int	The number of adjacent triangles

P0

Gets a value indicating the 1st point of this Tri.

Declaration

protected Coordinate P0 { get; }

Property Value

Type	Description
Coordinate

P1

Gets a value indicating the 2nd point of this Tri.

Declaration

protected Coordinate P1 { get; }

Property Value

Type	Description
Coordinate

P2

Gets a value indicating the 3rd point of this Tri.

Declaration

protected Coordinate P2 { get; }

Property Value

Type	Description
Coordinate

Tri0

Gets a value indicating the adjacent Tri across the edge P0 clockwise towards the next point.

Declaration

protected Tri Tri0 { get; }

Property Value

Type	Description
Tri

Tri1

Gets a value indicating the adjacent Tri across the edge P1 clockwise towards the next point.

Declaration

protected Tri Tri1 { get; }

Property Value

Type	Description
Tri

Tri2

Gets a value indicating the adjacent Tri across the edge P2 clockwise towards the next point.

Declaration

protected Tri Tri2 { get; }

Property Value

Type	Description
Tri

Methods

AreaOf(IEnumerable<Tri>)

Computes the area of a set of Tris.

Declaration

public static double AreaOf(IEnumerable<Tri> triList)

Parameters

Type	Name	Description
IEnumerable<Tri>	triList	A set of tris

Returns

Type	Description
double	The total area of the triangles

Create(Coordinate, Coordinate, Coordinate)

Creates a triangle with the given vertices. The vertices should be oriented clockwise.

Declaration

public static Tri Create(Coordinate p0, Coordinate p1, Coordinate p2)

Parameters

Type	Name	Description
Coordinate	p0	The first triangle vertex
Coordinate	p1	The second triangle vertex
Coordinate	p2	The third triangle vertex

Returns

Type	Description
Tri	The created trianlge

Create(Coordinate[])

Creates a triangle from an array with three vertex coordinates. The vertices should be oriented clockwise.

Declaration

public static Tri Create(Coordinate[] pts)

Parameters

Type	Name	Description
Coordinate[]	pts	The array of vertex coordinates

Returns

Type	Description
Tri	The created triangle

Degree(int, IList<Tri>)

Computes the degree of a Tri vertex, which is the number of tris containing it. This must be done by searching the entire triangulation, since the containing tris may not be adjacent or edge-connected.

Declaration

public int Degree(int index, IList<Tri> triList)

Parameters

Type	Name	Description
int	index	The vertex index
IList<Tri>	triList	The triangulation

Returns

Type	Description
int	The degree of the vertex

Flip(int)

Interchanges the vertices of this triangle and a neighbor so that their common edge becomes the the other diagonal of the quadrilateral they form. Neighbour triangle links are modified accordingly.

Declaration

public void Flip(int index)

Parameters

Type	Name	Description
int	index	The index of the adjacent tri to flip with

GetAdjacent(int)

Gets the triangle adjacent to an edge.

Declaration

public Tri GetAdjacent(int index)

Parameters

Type	Name	Description
int	index	The edge index

Returns

Type	Description
Tri	The adjacent triangle (may be null)

GetCoordinate(int)

Gets the coordinate for a vertex. This is the start vertex of the edge.

Declaration

public Coordinate GetCoordinate(int index)

Parameters

Type	Name	Description
int	index	The vertex (edge) index

Returns

Type	Description
Coordinate	The vertex coordinate

GetIndex(Coordinate)

Gets the index of the triangle vertex which has a given coordinate (if any). This is also the index of the edge which originates at the vertex.

Declaration

public int GetIndex(Coordinate p)

Parameters

Type	Name	Description
Coordinate	p	The coordinate to find

Returns

Type	Description
int	The vertex index, or -1 if it is not in the triangle

GetIndex(Tri)

Gets the edge index which a triangle is adjacent to (if any), based on the adjacent triangle link.

Declaration

public int GetIndex(Tri tri)

Parameters

Type	Name	Description
Tri	tri	The Tri to find

Returns

Type	Description
int	The index of the edge adjacent to the triangle, or -1 if not found

GetLength(int)

Gets the length of an edge of the triangle.

Declaration

public double GetLength(int edgeIndex)

Parameters

Type	Name	Description
int	edgeIndex	The edge index

Returns

Type	Description
double	The edge length

HasAdjacent()

Tests if this tri has any adjacent tris.

Declaration

public bool HasAdjacent()

Returns

Type	Description
bool	true if there is at least one adjacent tri

HasAdjacent(int)

Tests if there is an adjacent triangle to an edge.

Declaration

public bool HasAdjacent(int index)

Parameters

Type	Name	Description
int	index	The edge index

Returns

Type	Description
bool	true if there is a triangle adjacent to edge

IsAdjacent(Tri)

Tests if a triangle is adjacent to some edge of this triangle.

Declaration

public bool IsAdjacent(Tri tri)

Parameters

Type	Name	Description
Tri	tri	The triangle to test

Returns

Type	Description
bool	true if the triangle is adjacent

IsBorder()

Tests if a tri contains a boundary edge, and thus on the border of the triangulation containing it.

Declaration

public bool IsBorder()

Returns

Type	Description
bool	true if the tri is on the border of the triangulation

IsBoundary(int)

Tests if an edge is on the boundary of a triangulation.

Declaration

public bool IsBoundary(int index)

Parameters

Type	Name	Description
int	index	The index of an edge

Returns

Type	Description
bool	true if the edge is on the boundary

IsInteriorVertex(int)

Tests if a tri vertex is interior. A vertex of a triangle is interior if it is fully surrounded by other triangles.

Declaration

public bool IsInteriorVertex(int index)

Parameters

Type	Name	Description
int	index	The vertex index

Returns

Type	Description
bool	true if the vertex is interior

MidPoint(int)

Computes a coordinate for the midpoint of a triangle edge.

Declaration

public Coordinate MidPoint(int edgeIndex)

Parameters

Type	Name	Description
int	edgeIndex	The edge index

Returns

Type	Description
Coordinate	the midpoint of the triangle edge

Next(int)

Computes the vertex or edge index which is the next one (counter-clockwise) around the triangle.

Declaration

public static int Next(int index)

Parameters

Type	Name	Description
int	index	The index

Returns

Type	Description
int	The next index value

OppEdge(int)

Gets the index of the edge opposite a vertex.

Declaration

public static int OppEdge(int vertexIndex)

Parameters

Type	Name	Description
int	vertexIndex	The index of the vertex

Returns

Type	Description
int	The index of the opposite edge

OppVertex(int)

Gets the index of the vertex opposite an edge.

Declaration

public static int OppVertex(int edgeIndex)

Parameters

Type	Name	Description
int	edgeIndex	The edge index

Returns

Type	Description
int	The index of the opposite vertex

Prev(int)

Computes the vertex or edge index which is the previous one (counter-clockwise) around the triangle.

Declaration

public static int Prev(int index)

Parameters

Type	Name	Description
int	index	The index

Returns

Type	Description
int	The previous index value

Remove()

Removes this triangle from a triangulation. All adjacent references and the references to this Tri in the adjacent Tris are set to null.

Declaration

public void Remove()

Remove(IList<Tri>)

Removes this tri from the triangulation containing it. All links between the tri and adjacent ones are nulled.

Declaration

public void Remove(IList<Tri> triList)

Parameters

Type	Name	Description
IList<Tri>	triList	The triangulation

SetAdjacent(Coordinate, Tri)

Sets the triangle adjacent to the edge originating at a given vertex.
The vertices of the adjacent triangles are assumed to match the appropriate vertices in this triangle.

Declaration

public void SetAdjacent(Coordinate pt, Tri tri)

Parameters

Type	Name	Description
Coordinate	pt	The edge start point
Tri	tri	The adjacent triangle

SetAdjacent(Tri, Tri, Tri)

Sets the adjacent triangles.
The vertices of the adjacent triangles are assumed to match the appropriate vertices in this triangle.

Declaration

public void SetAdjacent(Tri tri0, Tri tri1, Tri tri2)

Parameters

Type	Name	Description
Tri	tri0	The triangle adjacent to edge 0
Tri	tri1	The triangle adjacent to edge 1
Tri	tri2	The triangle adjacent to edge 2

SetTri(int, Tri)

Sets the triangle adjacent to an edge.
The vertices of the adjacent triangle are assumed to match the appropriate vertices in this triangle.

Declaration

public void SetTri(int edgeIndex, Tri tri)

Parameters

Type	Name	Description
int	edgeIndex	The edge triangle is adjacent to
Tri	tri	The adjacent triangle

Split(Coordinate)

Splits a triangle by a point located inside the triangle. Creates the three new resulting triangles with adjacent links set correctly. Returns the new triangle whose 0'th vertex is the splitting point.

Declaration

public Tri Split(Coordinate p)

Parameters

Type	Name	Description
Coordinate	p	The point to insert

Returns

Type	Description
Tri	The new triangle whose 0'th vertex is p

ToGeometry(ICollection<Tri>, GeometryFactory)

Creates a GeometryCollection of NetTopologySuite.Triangulate.Polygons representing the triangles in a list.

Declaration

public static Geometry ToGeometry(ICollection<Tri> tris, GeometryFactory geomFact)

Parameters

Type	Name	Description
ICollection<Tri>	tris	A collection of Tris
GeometryFactory	geomFact	The GeometryFactory to use

Returns

Type	Description
Geometry	The Polygons for the triangles

ToPolygon(GeometryFactory)

Creates a NetTopologySuite.Triangulate.Polygon representing this triangle.

Declaration

public Polygon ToPolygon(GeometryFactory geomFact)

Parameters

Type	Name	Description
GeometryFactory	geomFact	The geometry factory

Returns

Type	Description
Polygon	A polygon

ToString()

Declaration

public override string ToString()

Returns

Type	Description
string

Overrides

object.ToString()

Validate()

Validates that a Tri is correct. Currently just checks that orientation is CW.

Declaration

public void Validate()

Exceptions

Type	Condition
ArgumentException	Thrown if Tri is not valid

Validate(IEnumerable<Tri>)

Validates a list of Tris.

Declaration

public static void Validate(IEnumerable<Tri> triList)

Parameters

Type	Name	Description
IEnumerable<Tri>	triList	The list of Tris to validate

ValidateAdjacent(int)

Validates that the vertices of an adjacent linked triangle are correct.

Declaration

public void ValidateAdjacent(int index)

Parameters

Type	Name	Description
int	index	The index of the adjacent triangle