here you go

`/*`

* Copyright (c) 2003-2007 jMonkeyEngine

* All rights reserved.

*

* Redistribution and use in source and binary forms, with or without

* modification, are permitted provided that the following conditions are

* met:

*

* * Redistributions of source code must retain the above copyright

* notice, this list of conditions and the following disclaimer.

*

* * Redistributions in binary form must reproduce the above copyright

* notice, this list of conditions and the following disclaimer in the

* documentation and/or other materials provided with the distribution.

*

* * Neither the name of 'jMonkeyEngine' nor the names of its contributors

* may be used to endorse or promote products derived from this software

* without specific prior written permission.

*

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED

* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR

* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

package com.jmex.simplephysics;

import java.io.IOException;

import java.io.Serializable;

import java.util.logging.Logger;

import com.jme.math.Triangle;

import com.jme.math.Vector3f;

import com.jme.util.export.InputCapsule;

import com.jme.util.export.JMEExporter;

import com.jme.util.export.JMEImporter;

import com.jme.util.export.OutputCapsule;

import com.jme.util.export.Savable;

/**

* <code>Plane</code> defines a plane where Normal dot (x,y,z) = Constant.

* This provides methods for calculating a "distance" of a point from this

* plane. The distance is pseudo due to the fact that it can be negative if the

* point is on the non-normal side of the plane.

*

* @author Mark Powell

* @version $Id: Plane.java,v 1.15 2007/09/21 15:45:26 nca Exp $

*/

public class Plane implements Serializable, Savable {

private static final Logger logger = Logger

.getLogger(Plane.class.getName());

private static final long serialVersionUID = 1L;

/**

* NO_SIDE represents the plane itself.

*/

public static final int NO_SIDE = 0;

/**

* POSITIVE_SIDE represents a point on the side the normal points.

*/

public static final int POSITIVE_SIDE = 1;

/**

* NEGATIVE_SIDE represents a point on the opposite side the normal points.

*/

public static final int NEGATIVE_SIDE = 2;

/** Vector normal to the plane. */

public Vector3f normal;

/** Constant of the plane. See formula in class definition. */

public float constant;

/**

* Constructor instantiates a new <code>Plane</code> object. This is the

* default object and contains a normal of (0,0,0) and a constant of 0.

*/

public Plane() {

normal = new Vector3f();

}

/**

* Constructor instantiates a new <code>Plane</code> object. The normal

* and constant values are set at creation.

*

* @param normal

* the normal of the plane.

* @param constant

* the constant of the plane.

*/

public Plane(Vector3f normal, float constant) {

if (normal == null) {

logger.warning("Normal was null, created default normal.");

normal = new Vector3f();

}

this.normal = normal;

this.constant = constant;

}

/**

* <code>setNormal</code> sets the normal of the plane.

*

* @param normal

* the new normal of the plane.

*/

public void setNormal(Vector3f normal) {

if (normal == null) {

logger.warning("Normal was null, created default normal.");

normal = new Vector3f();

}

this.normal = normal;

}

/**

* <code>getNormal</code> retrieves the normal of the plane.

*

* @return the normal of the plane.

*/

public Vector3f getNormal() {

return normal;

}

/**

* <code>setConstant</code> sets the constant value that helps define the

* plane.

*

* @param constant

* the new constant value.

*/

public void setConstant(float constant) {

this.constant = constant;

}

/**

* <code>getConstant</code> returns the constant of the plane.

*

* @return the constant of the plane.

*/

public float getConstant() {

return constant;

}

/**

* <code>pseudoDistance</code> calculates the distance from this plane to

* a provided point. If the point is on the negative side of the plane the

* distance returned is negative, otherwise it is positive. If the point is

* on the plane, it is zero.

*

* @param point

* the point to check.

* @return the signed distance from the plane to a point.

*/

public float pseudoDistance(Vector3f point) {

return normal.dot(point) - constant;

}

/**

* <code>whichSide</code> returns the side at which a point lies on the

* plane. The positive values returned are: NEGATIVE_SIDE, POSITIVE_SIDE and

* NO_SIDE.

*

* @param point

* the point to check.

* @return the side at which the point lies.

*/

public int whichSide(Vector3f point) {

float dis = pseudoDistance(point);

if (dis < 0) {

return NEGATIVE_SIDE;

} else if (dis > 0) {

return POSITIVE_SIDE;

} else {

return NO_SIDE;

}

}

/**

* Initialize this plane using the three points of the given triangle.

*

* @param t

* the triangle

*/

public void setPlanePoints(Triangle t) {

setPlanePoints(t.get(0), t.get(1), t.get(2));

}

/**

* Initialize the Plane using the given 3 points as coplanar.

*

* @param v1

* the first point

* @param v2

* the second point

* @param v3

* the third point

*/

public void setPlanePoints(Vector3f v1, Vector3f v2, Vector3f v3) {

normal.set(v2).subtractLocal(v1);

normal.crossLocal(v3.x - v1.x, v3.y - v1.y, v3.z - v1.z).normalizeLocal();

constant = -(normal.x * v1.x + normal.y * v1.y + normal.z * v1.z);

//normal.crossLocal(v3.x - v1.x, v3.y - v1.y, v3.z - v1.z).normalizeLocal();

//constant = -(normal.x * v1.x + normal.y * v1.y + normal.z * v1.z);

}

/**

* <code>toString</code> returns a string thta represents the string

* representation of this plane. It represents the normal as a

* <code>Vector3f</code> object, so the format is the following:

* com.jme.math.Plane [Normal: org.jme.math.Vector3f [X=XX.XXXX, Y=YY.YYYY,

* Z=ZZ.ZZZZ] - Constant: CC.CCCCC]

*

* @return the string representation of this plane.

*/

public String toString() {

return "com.jme.math.Plane [Normal: " + normal + " - Constant: "

+ constant + "]";

}

public void write(JMEExporter e) throws IOException {

OutputCapsule capsule = e.getCapsule(this);

capsule.write(normal, "normal", Vector3f.ZERO);

capsule.write(constant, "constant", 0);

}

public void read(JMEImporter e) throws IOException {

InputCapsule capsule = e.getCapsule(this);

normal = (Vector3f) capsule.readSavable("normal", Vector3f.ZERO.clone());

constant = capsule.readFloat("constant", 0);

}

public Class getClassTag() {

return this.getClass();

}

}