Class TrianglePredicate

Algorithms for computing values and predicates associated with triangles.

Inheritance

object

TrianglePredicate

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: NetTopologySuite.Triangulate.QuadEdge

Assembly: NetTopologySuite.dll

Syntax

public static class TrianglePredicate

Remarks

For some algorithms extended-precision implementations are provided, which are more robust (i.e. they produce correct answers in more cases). Also, some more robust formulations of some algorithms are provided, which utilize normalization to the origin.

Methods

IsInCircleCC(Coordinate, Coordinate, Coordinate, Coordinate)

Computes the inCircle test using distance from the circumcentre. Uses standard double-precision arithmetic.

Declaration

public static bool IsInCircleCC(Coordinate a, Coordinate b, Coordinate c, Coordinate p)

Parameters

Type	Name	Description
Coordinate	a	A vertex of the triangle
Coordinate	b	A vertex of the triangle
Coordinate	c	A vertex of the triangle
Coordinate	p	The point to test

Returns

Type	Description
bool	The area of a triangle defined by the points a, b and c

Remarks

In general this doesn't appear to be any more robust than the standard calculation. However, there is at least one case where the test point is far enough from the circumcircle that this test gives the correct answer.

LINESTRING (1507029.9878 518325.7547, 1507022.1120341457 518332.8225183258,
1507029.9833 518325.7458, 1507029.9896965567 518325.744909031)

IsInCircleDDFast(Coordinate, Coordinate, Coordinate, Coordinate)

Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise).

Declaration

public static bool IsInCircleDDFast(Coordinate a, Coordinate b, Coordinate c, Coordinate p)

Parameters

Type	Name	Description
Coordinate	a	A vertex of the triangle
Coordinate	b	A vertex of the triangle
Coordinate	c	A vertex of the triangle
Coordinate	p	The point to test

Returns

Type	Description
bool	true if this point is inside the circle defined by the points a, b, c

Remarks

The computation uses DD arithmetic for robustness, but a faster approach.

IsInCircleDDNormalized(Coordinate, Coordinate, Coordinate, Coordinate)

Declaration

public static bool IsInCircleDDNormalized(Coordinate a, Coordinate b, Coordinate c, Coordinate p)

Parameters

Type	Name	Description
Coordinate	a
Coordinate	b
Coordinate	c
Coordinate	p

Returns

Type	Description
bool

IsInCircleNonRobust(Coordinate, Coordinate, Coordinate, Coordinate)

Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise). This test uses simple double-precision arithmetic, and thus is not 100% robust.

Declaration

public static bool IsInCircleNonRobust(Coordinate a, Coordinate b, Coordinate c, Coordinate p)

Parameters

Type	Name	Description
Coordinate	a	A vertex of the triangle
Coordinate	b	A vertex of the triangle
Coordinate	c	A vertex of the triangle
Coordinate	p	The point to test

Returns

Type	Description
bool	true if this point is inside the circle defined by the points a, b, c

IsInCircleNormalized(Coordinate, Coordinate, Coordinate, Coordinate)

Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise).

Declaration

public static bool IsInCircleNormalized(Coordinate a, Coordinate b, Coordinate c, Coordinate p)

Parameters

Type	Name	Description
Coordinate	a	A vertex of the triangle
Coordinate	b	A vertex of the triangle
Coordinate	c	A vertex of the triangle
Coordinate	p	The point to test

Returns

Type	Description
bool	true if this point is inside the circle defined by the points a, b, c

Remarks

This test uses simple double-precision arithmetic, and thus is not 100% robust. However, by using normalization to the origin it provides improved robustness and increased performance.

Based on code by J.R.Shewchuk.

IsInCircleRobust(Coordinate, Coordinate, Coordinate, Coordinate)

Tests if a point is inside the circle defined by the triangle with vertices a, b, c (oriented counter-clockwise).

Declaration

public static bool IsInCircleRobust(Coordinate a, Coordinate b, Coordinate c, Coordinate p)

Parameters

Type	Name	Description
Coordinate	a	A vertex of the triangle
Coordinate	b	A vertex of the triangle
Coordinate	c	A vertex of the triangle
Coordinate	p	The point to test

Returns

Type	Description
bool	true if this point is inside the circle defined by the points a, b, c

Remarks

This method uses more robust computation.