AMPlane.java

package am2.api.math;

public class AMPlane {
	AMVector3 planeDef[];

	public AMPlane(AMVector3...plane){
		planeDef = plane;
	}

	private AMVector3 planeNormal(){
		AMVector3 vVector1 = new AMVector3(planeDef[2], planeDef[0]);
		AMVector3 vVector2 = new AMVector3(planeDef[1], planeDef[0]);

		AMVector3 vNormal = AMVector3.crossProduct(vVector1, vVector2);

		vNormal.normalize();
		return vNormal;
	}

	private float planeDistance(AMVector3 normal, AMVector3 point){
		float distance = 0;
		distance = - ((normal.x * point.x) + (normal.y * point.y) + (normal.z * point.z));

		return distance;
	}

	public boolean lineSegmentCrosses(AMVector3 p1, AMVector3 p2){
		float distance1=0, distance2=0;

		AMVector3 vNormal = planeNormal();

		float originDistance = planeDistance(vNormal, planeDef[0]);

		distance1 = ((vNormal.x * p1.x)  +					// Ax +
				(vNormal.y * p1.y)  +					// Bx +
				(vNormal.z * p1.z)) + originDistance;	// Cz + D

		distance2 = ((vNormal.x * p2.x)  +					// Ax +
				(vNormal.y * p2.y)  +					// Bx +
				(vNormal.z * p2.z)) + originDistance;	// Cz + D

		if(distance1 * distance2 >= 0)			// Check to see if both point's distances are both negative or both positive
			return false;						// Return false if each point has the same sign.  -1 and 1 would mean each point is on either side of the plane.  -1 -2 or 3 4 wouldn't...

		return true;							// The line intersected the plane, Return TRUE
	}
}