javax.media.j3d
Class BoundingPolytope

java.lang.Object
  javax.media.j3d.Bounds
      javax.media.j3d.BoundingPolytope

All Implemented Interfaces:

java.lang.Cloneable

public class BoundingPolytope
extends Bounds

A BoundingPolytope defines a polyhedral bounding region using the intersection of four or more half spaces. The region defined by a BoundingPolytope is always convex and must be closed.

Each plane in the BoundingPolytope specifies a half-space defined by the equation:

Ax + By + Cz + D <= 0

where A, B, C, D are the parameters that specify the plane. The parameters are passed in the x, y, z, and w fields, respectively, of a Vector4d object. The intersection of the set of half-spaces corresponding to the planes in this BoundingPolytope defines the bounding region.

Constructor Summary

BoundingPolytope()
Constructs a BoundingPolytope and initializes it to a set of 6 planes that defines a cube such that -1 <= x,y,z <= 1.

BoundingPolytope(Bounds boundsObject)
Constructs a BoundingPolytope from the specified bounds object.

BoundingPolytope(Bounds[] boundsObjects)
Constructs a BoundingPolytope from the specified array of bounds objects.

BoundingPolytope(Vector4d[] planes)
Constructs a BoundingPolytope using the specified planes.

Method Summary

java.lang.Object	clone() Creates a copy of a polytope.
Bounds	closestIntersection(Bounds[] boundsObjects) Finds closest bounding object that intersects this bounding polytope.
void	combine(Bounds boundsObject) Combines this bounding polytope with a bounding object so that the resulting bounding polytope encloses the original bounding polytope and the given bounds object.
void	combine(Bounds[] boundsObjects) Combines this bounding polytope with an array of bounding objects so that the resulting bounding polytope encloses the original bounding polytope and the given array of bounds object.
void	combine(Point3d point) Combines this bounding polytope with a point.
void	combine(Point3d[] points) Combines this bounding polytope with an array of points.
boolean	equals(java.lang.Object bounds) Indicates whether the specified bounds object is equal to this BoundingPolytope object.
void	getCenter(Point3d center) Gets the centroid of this bounding region.
int	getNumPlanes()
void	getPlanes(Vector4d[] planes) Returns the equations of the bounding planes for this bounding polytope.
int	hashCode() Returns a hash code value for this BoundingPolytope object based on the data values in this object.
boolean	intersect(Bounds boundsObject) Test for intersection with another bounds object.
boolean	intersect(Bounds[] boundsObjects) Test for intersection with another bounds object.
boolean	intersect(Bounds[] boundsObjects, BoundingPolytope newBoundingPolytope) Test for intersection with an array of bounds objects.
boolean	intersect(Bounds boundsObject, BoundingPolytope newBoundPolytope) Test for intersection with another bounds object.
boolean	intersect(Point3d point) Test for intersection with a point.
boolean	intersect(Point3d origin, Vector3d direction) Test for intersection with a ray.
boolean	isEmpty() Tests whether the bounding polytope is empty.
void	set(Bounds boundsObject) Sets the planes for this BoundingPolytope by keeping its current number and position of planes and computing new planes positions to enclose the given bounds object.
void	setPlanes(Vector4d[] planes) Sets the bounding planes for this polytope.
java.lang.String	toString() Returns a string representation of this class
void	transform(Bounds boundsObject, Transform3D matrix) Modifies the bounding polytope so that it bounds the volume generated by transforming the given bounding object.
void	transform(Transform3D matrix) Transforms this bounding polytope by the given transformation matrix.

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

BoundingPolytope

public BoundingPolytope(Vector4d[] planes)

Constructs a BoundingPolytope using the specified planes.

Parameters:

planes - a set of planes defining the polytope.

Throws:

java.lang.IllegalArgumentException - if the length of the specified array of planes is less than 4.

BoundingPolytope

public BoundingPolytope()

Constructs a BoundingPolytope and initializes it to a set of 6 planes that defines a cube such that -1 <= x,y,z <= 1. The values of the planes are as follows:

planes[0] : x <= 1 (1,0,0,-1)
planes[1] : -x <= 1 (-1,0,0,-1)
planes[2] : y <= 1 (0,1,0,-1)
planes[3] : -y <= 1 (0,-1,0,-1)
planes[4] : z <= 1 (0,0,1,-1)
planes[5] : -z <= 1 (0,0,-1,-1)

BoundingPolytope

public BoundingPolytope(Bounds boundsObject)

Constructs a BoundingPolytope from the specified bounds object. The new polytope will circumscribe the region specified by the input bounds.

Parameters:

boundsObject - the bounds object from which this polytope is constructed.

BoundingPolytope

public BoundingPolytope(Bounds[] boundsObjects)

Constructs a BoundingPolytope from the specified array of bounds objects. The new polytope will circumscribe the union of the regions specified by the input bounds objects.

Parameters:

boundsObjects - the array bounds objects from which this polytope is constructed.

Method Detail

setPlanes

public void setPlanes(Vector4d[] planes)

Sets the bounding planes for this polytope.

Parameters:

planes - the new set of planes for this polytope

Throws:

java.lang.IllegalArgumentException - if the length of the specified array of planes is less than 4.

getPlanes

public void getPlanes(Vector4d[] planes)

Returns the equations of the bounding planes for this bounding polytope. The equations are copied into the specified array. The array must be large enough to hold all of the vectors. The individual array elements must be allocated by the caller.

Parameters:

planes - an array Vector4d to receive the bounding planes

getNumPlanes

public int getNumPlanes()

set

public void set(Bounds boundsObject)

Sets the planes for this BoundingPolytope by keeping its current number and position of planes and computing new planes positions to enclose the given bounds object.

Specified by:

set in class Bounds

Parameters:

boundsObject - another bounds object

clone

public java.lang.Object clone()

Creates a copy of a polytope.

Specified by:

clone in class Bounds

Returns:

a new BoundingPolytope

equals

public boolean equals(java.lang.Object bounds)

Indicates whether the specified bounds object is equal to this BoundingPolytope object. They are equal if the specified bounds object is an instance of BoundingPolytope and all of the data members of bounds are equal to the corresponding data members in this BoundingPolytope.

Specified by:

equals in class Bounds

Parameters:

bounds - the object with which the comparison is made.

Returns:

true if this BoundingPolytope is equal to bounds; otherwise false

Since:

Java 3D 1.2

hashCode

public int hashCode()

Returns a hash code value for this BoundingPolytope object based on the data values in this object. Two different BoundingPolytope objects with identical data values (i.e., BoundingPolytope.equals returns true) will return the same hash code value. Two BoundingPolytope objects with different data members may return the same hash code value, although this is not likely.

Specified by:

hashCode in class Bounds

Returns:

a hash code value for this BoundingPolytope object.

Since:

Java 3D 1.2

combine

public void combine(Bounds boundsObject)

Combines this bounding polytope with a bounding object so that the resulting bounding polytope encloses the original bounding polytope and the given bounds object.

Specified by:

combine in class Bounds

Parameters:

boundsObject - another bounds object

combine

public void combine(Bounds[] boundsObjects)

Combines this bounding polytope with an array of bounding objects so that the resulting bounding polytope encloses the original bounding polytope and the given array of bounds object.

Specified by:

combine in class Bounds

Parameters:

boundsObjects - an array of bounds objects

combine

public void combine(Point3d point)

Combines this bounding polytope with a point.

Specified by:

combine in class Bounds

Parameters:

point - a 3d point in space

combine

public void combine(Point3d[] points)

Combines this bounding polytope with an array of points.

Specified by:

combine in class Bounds

Parameters:

points - an array of 3d points in space

transform

public void transform(Bounds boundsObject,
                      Transform3D matrix)

Modifies the bounding polytope so that it bounds the volume generated by transforming the given bounding object.

Specified by:

transform in class Bounds

Parameters:

boundsObject - the bounding object to be transformed

matrix - a transformation matrix

transform

public void transform(Transform3D matrix)

Transforms this bounding polytope by the given transformation matrix.

Specified by:

transform in class Bounds

Parameters:

matrix - a transformation matrix

intersect

public boolean intersect(Point3d origin,
                         Vector3d direction)

Test for intersection with a ray.

Specified by:

intersect in class Bounds

Parameters:

origin - the starting point of the ray

direction - the direction of the ray

Returns:

true or false indicating if an intersection occured

isEmpty

public boolean isEmpty()

Tests whether the bounding polytope is empty. A bounding polytope is empty if it is null (either by construction or as the result of a null intersection) or if its volume is negative. A bounding polytope with a volume of zero is not empty.

Specified by:

isEmpty in class Bounds

Returns:

true if the bounding polytope is empty; otherwise, it returns false

intersect

public boolean intersect(Point3d point)

Test for intersection with a point.

Specified by:

intersect in class Bounds

Parameters:

point - a Point defining a position in 3-space

Returns:

true or false indicating if an intersection occured

intersect

public boolean intersect(Bounds boundsObject)

Test for intersection with another bounds object.

Specified by:

intersect in class Bounds

Parameters:

boundsObject - another bounds object

Returns:

true or false indicating if an intersection occured

intersect

public boolean intersect(Bounds[] boundsObjects)

Test for intersection with another bounds object.

Specified by:

intersect in class Bounds

Parameters:

boundsObjects - an array of bounding objects

Returns:

true or false indicating if an intersection occured

intersect

public boolean intersect(Bounds boundsObject,
                         BoundingPolytope newBoundPolytope)

Test for intersection with another bounds object.

Parameters:

boundsObject - another bounds object

newBoundPolytope - the new bounding polytope, which is the intersection of the boundsObject and this BoundingPolytope

Returns:

true or false indicating if an intersection occured

intersect

public boolean intersect(Bounds[] boundsObjects,
                         BoundingPolytope newBoundingPolytope)

Test for intersection with an array of bounds objects.

Parameters:

boundsObjects - an array of bounds objects

newBoundingPolytope - the new bounding polytope, which is the intersection of the boundsObject and this BoundingPolytope

Returns:

true or false indicating if an intersection occured

closestIntersection

public Bounds closestIntersection(Bounds[] boundsObjects)

Finds closest bounding object that intersects this bounding polytope.

Specified by:

closestIntersection in class Bounds

Parameters:

boundsObjects - is an array of bounds objects

Returns:

closest bounding object

toString

public java.lang.String toString()

Returns a string representation of this class

Overrides:

toString in class java.lang.Object

getCenter

public void getCenter(Point3d center)

Description copied from class: Bounds

Gets the centroid of this bounding region.

Specified by:

getCenter in class Bounds

Parameters:

center - a Point to receive the centroid of the bounding region