C# Class Loyc.Geometry.PolygonMath

Contains useful basic polygon algorithms: hit testing, area calculation, orientation detection.

Datei anzeigen Open project: qwertie/ecsharp Class Usage Examples

Public Methods

Method	Description
GetWindingNumber ( this poly, System.Point p ) : int	Counts the number of times the polygon winds around a test point, using a rightward raycasting test. The test point is considered to be within the polygon if it lies on a top or left edge, but not on a bottom or right edge (within the precision limits of 'double' arithmetic). The test point will never be considered inside a degenerate (zero-width) area.
IsPointInPolygon ( IEnumerable poly, System.Point p ) : bool	Finds out if a point is inside the polygon using a winding test.
IsPointInPolygon ( IEnumerator e, System.Point p ) : bool
Orientation ( IEnumerable poly ) : int	Returns Math.Sign(PolygonArea(poly)): positive when clockwise and increasing Y goes upward. A common approach to this problem is to look at the topmost point and the two points on either side. However, if one is not careful, this technique may be unable to detect the orientation in case the polygon has duplicate points, horizontal lines on top, or a degenerate top in which the top part of the polygon is zero-width (these problems can occur even if the polygon's lines do not cross one another.) That's why I chose to compute orientation based on area instead.
Orientation ( IEnumerator poly ) : int
PolygonArea ( IEnumerable polygon ) : FPL16	Computes the area of a polygon. http://www.codeproject.com/Tips/601272/Calculating-the-area-of-a-polygon
PolygonArea ( IEnumerator e ) : FPL16
PolygonArea ( IEnumerable polygon ) : FPL32	Computes the area of a polygon. http://www.codeproject.com/Tips/601272/Calculating-the-area-of-a-polygon
PolygonArea ( IEnumerator e ) : FPL32
PolygonArea ( IEnumerable polygon ) : double	Computes the area of a polygon. http://www.codeproject.com/Tips/601272/Calculating-the-area-of-a-polygon
PolygonArea ( IEnumerator e ) : double
PolygonArea ( IEnumerable polygon ) : float	Computes the area of a polygon. http://www.codeproject.com/Tips/601272/Calculating-the-area-of-a-polygon
PolygonArea ( IEnumerator e ) : float
PolygonArea ( IEnumerable polygon ) : long	Computes the area of a polygon. http://www.codeproject.com/Tips/601272/Calculating-the-area-of-a-polygon
PolygonArea ( IEnumerator e ) : long

Private Methods

Method	Description
GWN_NextLine ( System.Point p, System.Point p1, System.Point p2 ) : int

Method Details

GetWindingNumber() public static method

Counts the number of times the polygon winds around a test point, using a rightward raycasting test.

The test point is considered to be within the polygon if it lies on a top or left edge, but not on a bottom or right edge (within the precision limits of 'double' arithmetic). The test point will never be considered inside a degenerate (zero-width) area.

public static GetWindingNumber ( this poly, System.Point p ) : int
poly	this
p	System.Point
return	int

IsPointInPolygon() public static method

Finds out if a point is inside the polygon using a winding test.

public static IsPointInPolygon ( IEnumerable poly, System.Point p ) : bool
poly	IEnumerable
p	System.Point
return	bool

IsPointInPolygon() public static method

public static IsPointInPolygon ( IEnumerator e, System.Point p ) : bool
e	IEnumerator
p	System.Point
return	bool

Orientation() public static method

Returns Math.Sign(PolygonArea(poly)): positive when clockwise and increasing Y goes upward.

A common approach to this problem is to look at the topmost point and the two points on either side. However, if one is not careful, this technique may be unable to detect the orientation in case the polygon has duplicate points, horizontal lines on top, or a degenerate top in which the top part of the polygon is zero-width (these problems can occur even if the polygon's lines do not cross one another.) That's why I chose to compute orientation based on area instead.

public static Orientation ( IEnumerable poly ) : int
poly	IEnumerable
return	int