/*
 * Moonlight|3D Copyright (C) 2006 The Moonlight|3D team
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 * 
 * Created on Oct 31, 2006
 */
package ml.math;

public class Ray2D {
	public Vector2D start, direction;
	
	public Ray2D() {
		start=new Vector2D();
		direction=new Vector2D();
	}
	
	public Ray2D(Vector2D start, Vector2D direction) {
		this.start=start.clone();
		this.direction=direction.clone();
	}
	
	public Vector2D getIntersectionPoint(Line2D line) {
		Vector2D otherDirection;
		double lambda, tau;
		
		otherDirection=line.end2.sub(line.end1);
		
		double denominator=(-direction.X1*otherDirection.X2+direction.X2*otherDirection.X1);
		
		if(denominator==0) {
			return null; // lines are parallel - no intersection possible
		}
		
		tau = (-direction.X1*start.X2+direction.X1*line.end1.X2+direction.X2*start.X1-direction.X2*line.end1.X1)/denominator;
		lambda = -(-start.X1*otherDirection.X2+line.end1.X1*otherDirection.X2+otherDirection.X1*start.X2-otherDirection.X1*line.end1.X2)/denominator;
		
		if(!(0 <= tau && tau <=1) || !(0 <= lambda)) {
			// calculated intersection point is outside of at least one line - so no intersection
			return null;
		}
		
		Vector2D intersectionPoint=start.add(direction.multiply(lambda));
		
		return intersectionPoint;
	}

	public Vector2D getIntersectionPoint(Ray2D ray) {
		Vector2D otherDirection;
		double lambda, tau;
		
		otherDirection=ray.direction;
		
		double denominator=(-direction.X1*otherDirection.X2+direction.X2*otherDirection.X1);
		
		if(denominator==0) {
			return null; // lines are parallel - no intersection possible
		}
		
		tau = (-direction.X1*start.X2+direction.X1*ray.start.X2+direction.X2*start.X1-direction.X2*ray.start.X1)/denominator;
		lambda = -(-start.X1*otherDirection.X2+ray.start.X1*otherDirection.X2+otherDirection.X1*start.X2-otherDirection.X1*ray.start.X2)/denominator;
		
		if(!(0 <= tau) || !(0 <= lambda)) {
			// calculated intersection point is outside of at least one ray - so no intersection
			return null;
		}
		
		Vector2D intersectionPoint=start.add(direction.multiply(lambda));
		
		return intersectionPoint;
	}
}