// PhotonPath.java
// This class calculates and stores a photons path through a cloud using 
// a given cloud and scattering model.

import java.util.*;

public class PhotonPath {
	public PhotonPath(Cloud c,ScatteringModel s,RTVector mu) {
		in_dir=new RTVector(mu);
		current_dir=in_dir;
		current_r=c.RandomStartLocation(in_dir);
		path=new Vector(20,10);
		cloud=c;
		sm=s;
		path.addElement(current_r);
	}

	// You can call the Follow function to have the photon followed for a certain
	// number of steps.  When it returns true then the photon has left the cloud and
	// there is no point calling Follow any more so create another PhotonPath and do
	// another one.
	public boolean Follow(int max_steps) {
		int step;
		RTVector tmp_r;

		if(!cloud.IsInCloud(current_r)) return(true);
		for(step=0; step<max_steps; step++) {
			tmp_r=cloud.ScatterAt(current_r,current_dir);
			path_length+=RTVector.DistBetween(tmp_r,current_r);
			current_r=tmp_r;
			current_dir=sm.ScatteringDirection(current_dir);
			path.addElement(current_r);
			if(!cloud.IsInCloud(current_r)) return(true);
		}
		if(cloud.IsInCloud(current_r)) return(false);
		return(true);
	}

	public double GetPathLength() {
		return(path_length);
	}

	public Vector GetPath() {
		return(path);
	}

	public boolean WasTransmitted() {
		return((!cloud.IsInCloud(current_r)) && (cloud.IsBelowCloud(current_r)));
	}

	private double path_length=0;
	private RTVector current_r=null,current_dir=null;
	private Vector path=null;
	private Cloud cloud=null;
	private ScatteringModel sm=null;
	private RTVector in_dir=null,out_dir=null;
}