com.badlogic.gdx.math

Class GeometryUtils

java.lang.Object

com.badlogic.gdx.math.GeometryUtils

public final class GeometryUtils
extends Object

Author:

Nathan Sweet

Constructor Summary

Constructors

Constructor and Description
GeometryUtils()

Method Summary

Methods

Modifier and Type	Method and Description
static boolean	barycoordInsideTriangle(Vector2 barycentric) Returns true if the barycentric coordinates are inside the triangle.
static boolean	colinear(float x1, float y1, float x2, float y2, float x3, float y3)
static void	ensureCCW(float[] polygon)
static float	fromBarycoord(Vector2 barycentric, float a, float b, float c) Returns an interpolated value given the barycentric coordinates of a point in a triangle and the values at each vertex.
static Vector2	fromBarycoord(Vector2 barycentric, Vector2 a, Vector2 b, Vector2 c, Vector2 interpolatedOut) Returns interpolated values given the barycentric coordinates of a point in a triangle and the values at each vertex.
static float	lowestPositiveRoot(float a, float b, float c) Returns the lowest positive root of the quadric equation given by a* x * x + b * x + c = 0.
static float	polygonArea(float[] polygon, int offset, int count) Computes the area for a convex polygon.
static Vector2	polygonCentroid(float[] polygon, int offset, int count, Vector2 centroid) Returns the centroid for the specified non-self-intersecting polygon.
static Vector2	quadrilateralCentroid(float x1, float y1, float x2, float y2, float x3, float y3, float x4, float y4, Vector2 centroid)
static Vector2	toBarycoord(Vector2 p, Vector2 a, Vector2 b, Vector2 c, Vector2 barycentricOut) Computes the barycentric coordinates v,w for the specified point in the triangle.
static float	triangleArea(float x1, float y1, float x2, float y2, float x3, float y3)
static Vector2	triangleCentroid(float x1, float y1, float x2, float y2, float x3, float y3, Vector2 centroid)
static Vector2	triangleCircumcenter(float x1, float y1, float x2, float y2, float x3, float y3, Vector2 circumcenter) Returns the circumcenter of the triangle.

Methods inherited from class java.lang.Object

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

Constructor Detail

GeometryUtils

public GeometryUtils()

Method Detail

toBarycoord

public static Vector2 toBarycoord(Vector2 p,
                  Vector2 a,
                  Vector2 b,
                  Vector2 c,
                  Vector2 barycentricOut)

Computes the barycentric coordinates v,w for the specified point in the triangle.

If barycentric.x >= 0 && barycentric.y >= 0 && barycentric.x + barycentric.y <= 1 then the point is inside the triangle.

If vertices a,b,c have values aa,bb,cc then to get an interpolated value at point p:

 GeometryUtils.barycentric(p, a, b, c, barycentric);
 float u = 1.f - barycentric.x - barycentric.y;
 float x = u * aa.x + barycentric.x * bb.x + barycentric.y * cc.x;
 float y = u * aa.y + barycentric.x * bb.y + barycentric.y * cc.y;
 

Returns:

barycentricOut

barycoordInsideTriangle

public static boolean barycoordInsideTriangle(Vector2 barycentric)

Returns true if the barycentric coordinates are inside the triangle.

fromBarycoord

public static Vector2 fromBarycoord(Vector2 barycentric,
                    Vector2 a,
                    Vector2 b,
                    Vector2 c,
                    Vector2 interpolatedOut)

Returns interpolated values given the barycentric coordinates of a point in a triangle and the values at each vertex.

Returns:

interpolatedOut

fromBarycoord

public static float fromBarycoord(Vector2 barycentric,
                  float a,
                  float b,
                  float c)

Returns an interpolated value given the barycentric coordinates of a point in a triangle and the values at each vertex.

Returns:

interpolatedOut

lowestPositiveRoot

public static float lowestPositiveRoot(float a,
                       float b,
                       float c)

Returns the lowest positive root of the quadric equation given by a* x * x + b * x + c = 0. If no solution is given Float.Nan is returned.

Parameters:

a - the first coefficient of the quadric equation

b - the second coefficient of the quadric equation

c - the third coefficient of the quadric equation

Returns:

the lowest positive root or Float.Nan

colinear

public static boolean colinear(float x1,
               float y1,
               float x2,
               float y2,
               float x3,
               float y3)

triangleCentroid

public static Vector2 triangleCentroid(float x1,
                       float y1,
                       float x2,
                       float y2,
                       float x3,
                       float y3,
                       Vector2 centroid)

triangleCircumcenter

public static Vector2 triangleCircumcenter(float x1,
                           float y1,
                           float x2,
                           float y2,
                           float x3,
                           float y3,
                           Vector2 circumcenter)

Returns the circumcenter of the triangle. The input points must not be colinear.

triangleArea

public static float triangleArea(float x1,
                 float y1,
                 float x2,
                 float y2,
                 float x3,
                 float y3)

quadrilateralCentroid

public static Vector2 quadrilateralCentroid(float x1,
                            float y1,
                            float x2,
                            float y2,
                            float x3,
                            float y3,
                            float x4,
                            float y4,
                            Vector2 centroid)

polygonCentroid

public static Vector2 polygonCentroid(float[] polygon,
                      int offset,
                      int count,
                      Vector2 centroid)

Returns the centroid for the specified non-self-intersecting polygon.

polygonArea

public static float polygonArea(float[] polygon,
                int offset,
                int count)

Computes the area for a convex polygon.

ensureCCW

public static void ensureCCW(float[] polygon)