edu.eside.flingbox.math
Class PolygonUtils

java.lang.Object
  edu.eside.flingbox.math.PolygonUtils

public final class PolygonUtils
extends java.lang.Object

Implements some utilities for polygons.

Method Summary

static Vector2D[]	computePolygonNormals(Vector2D[] contour) Computes the polygon's normals.
static float	distanceFromLineToPoint(Vector2D p0, Vector2D p1, Vector2D p) Computes minimum distance from line to point
static Vector2D[]	douglasPeuckerReducer(Vector2D[] points, float epsilon) The Douglas-Peucker algorithm is an algorithm for reducing the number of points in a curve that is approximated by a series of points.
static float	polygonArea(Vector2D[] Vector2Ds) Computes area of polygon.
static Vector2D	polygonCentroid(Vector2D[] contour) Computes the polygon's centroid
static boolean	polygonConatinsPoint(Vector2D[] polygon, Vector2D Vector2D) Checks if a Vector2D is contained by a polygon.
static short[]	triangulatePolygon(Vector2D[] Vector2Ds) Computes the triangulation of a polygon(tesellation) with ear-clipping algorithm.

Methods inherited from class java.lang.Object

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

Method Detail

douglasPeuckerReducer

public static Vector2D[] douglasPeuckerReducer(Vector2D[] points,
                                               float epsilon)

The Douglas-Peucker algorithm is an algorithm for reducing the number of points in a curve that is approximated by a series of points. The end of this function is a good moment to call the GarbageCollector

Parameters:

points - Array of the polygon's points

epsilon - Max distance to ignore a point

Returns:

New array with optimized points

triangulatePolygon

public static short[] triangulatePolygon(Vector2D[] Vector2Ds)

Computes the triangulation of a polygon(tesellation) with ear-clipping algorithm.

Parameters:

Vector2Ds - Array of polygon's points

Returns:

Will return n-2 group of 3 points, for n sides polygon or null if not enough points

polygonConatinsPoint

public static boolean polygonConatinsPoint(Vector2D[] polygon,
                                           Vector2D Vector2D)

Checks if a Vector2D is contained by a polygon. It's based on Winding number algorithm. More info at http://en.wikipedia.org/wiki/Winding_number

Parameters:

polygon - polygon's Vector2Ds

Vector2D - Vector2D to be checked

polygonArea

public static float polygonArea(Vector2D[] Vector2Ds)

Computes area of polygon.

Parameters:

Vector2Ds - Polygon's Vector2Ds

Returns:

Polygon's area. if Vector2Ds are counter-clockwise the result will be positive, else it'll be negative

polygonCentroid

public static Vector2D polygonCentroid(Vector2D[] contour)

Computes the polygon's centroid

Parameters:

Vector2Ds - Polygon's Vector2Ds

Returns:

centroid

computePolygonNormals

public static Vector2D[] computePolygonNormals(Vector2D[] contour)

Computes the polygon's normals.

Parameters:

contour - Counterclockwise polygon points

Returns:

Polygon's normals

distanceFromLineToPoint

public static float distanceFromLineToPoint(Vector2D p0,
                                            Vector2D p1,
                                            Vector2D p)

Computes minimum distance from line to point