Package org.robwork.sdurw_geometry

Class PolygonUtil

java.lang.Object

org.robwork.sdurw_geometry.PolygonUtil

public class PolygonUtil
extends java.lang.Object

Utility functions for operations on polygons, such as convex partitioning.

The algorithm for convex partitioning of polygons has time complexity O(n r^2 \log r)
where n is the number of vertices and r is the number of reflex vertices (vertices that gives
an inward notch). The algorithm is due to J. Mark Keil [1]. For more information, see also
[2] and [3]. The polygons must not contain holes, and no new vertices are introduced (no
Steiner points).

[1] Minimum Decompostions of Polygonal Objects. J. Mark Keil. 1985.

[2] http://cgm.cs.mcgill.ca/~athens/cs644/Projects/2004/LiliSang-YunjunLiu/project/MAIN3.htm

[3] On the time bound for convex decomposition of simple polygons. Mark Keil & Jack Snoeyink.
1998. 10th Canadian Conference on Computational Geometry, Aug 1998. See
http://www.cs.ubc.ca/~snoeyink/convdecomp for full version paper.

Constructor Summary

Constructors

Constructor	Description
PolygonUtil(long cPtr, boolean cMemoryOwn)

Method Summary

Modifier and Type	Method	Description
static double	area(Polygon2D polygon)	Get the signed area of a 2D polygon.
static SWIGTYPE_p_std__vectorT_rw__geometry__PolygonT_rw__math__Vector2DT_double_t_t_t	convexDecomposition(Polygon2D polygon)	Convex decomposition of a polygon.
static VecotrVecotrULong	convexDecompositionIndexed(Polygon2D polygon)	Convex decomposition of a polygon.
void	delete()
static long	getCPtr(PolygonUtil obj)
static boolean	isInsideConvex(Vector2D point, Polygon2D polygon, double eps)	Check if point lies inside convex polygon.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PolygonUtil

public PolygonUtil(long cPtr,
                   boolean cMemoryOwn)

Method Detail

getCPtr

public static long getCPtr(PolygonUtil obj)

delete

public void delete()

convexDecompositionIndexed

public static VecotrVecotrULong convexDecompositionIndexed(Polygon2D polygon)

Convex decomposition of a polygon.

Parameters:

polygon - [in] the polygon to decompose into convex subpolygons.

Returns:

a vector of indexed polygons. Each indexed polygon is returned as an ordered
vector of indices.

convexDecomposition

public static SWIGTYPE_p_std__vectorT_rw__geometry__PolygonT_rw__math__Vector2DT_double_t_t_t convexDecomposition(Polygon2D polygon)

Convex decomposition of a polygon.

Parameters:

polygon - [in] the polygon to decompose into convex subpolygons.

Returns:

a vector of convex polygons.

isInsideConvex

public static boolean isInsideConvex(Vector2D point,
                                     Polygon2D polygon,
                                     double eps)

Check if point lies inside convex polygon.

Parameters:

point - [in] the point.

polygon - [in] the polygon.

eps - [in] distance threshold for when to consider a point inside the polygon.

Returns:

true if point is strictly inside the polygon, or false if on the border or
outside.

area

public static double area(Polygon2D polygon)

Get the signed area of a 2D polygon.

Parameters:

polygon - [in] the polygon to find area of.

Returns:

area of the polygon, with negative sign if vertices are given clockwise, or
positive sign if given counter-clockwise.