// Slab3D.java
// This class implements a 3D slab cloud.

import java.awt.*;
import java.util.*;

public class Slab3D extends Cloud {
	public int Dimension() {
		return(3);
	}

	public Slab3D(double od) {
		int i;

		data=new DataSet2D(20,10);
		data.SetSortOrder(DataSet2D.SORT_Y);
		for(i=0; i<20; i++) {
			data.AddElement(new Point2D(od,(double)i/19.0));
		}
	}

	// The only requirement to use this ScatterAt function is that when the
	// last component of the vector is zero you are out of the cloud.
	public RTVector ScatterAt(RTVector r,RTVector dir) {
		RTVector ret=new RTVector(r),next;
		double tau,p;
		double density1,density2;

		dir.Normalize();
		// First calculate an optical depth to use.
		p=Math.random();
		if(p<1e-3) {
			if(dir.Get(2)<0.0) {
				ret.Set(ret.Dimension()-1,0.0);
			} else {
				ret.Set(ret.Dimension()-1,1.01);
			}
			return(ret);
		}
		tau=-Math.log(p);

		// Now figure out where that is in the cloud.
		while(tau>0.0) {
			density1=this.OpticalDensity(ret);
			next=ret.Add(dir.Scale(0.01));
			density2=this.OpticalDensity(next);
			if(tau<(density1+density2)*0.01) {
				ret=ret.Add(dir.Scale(0.01*tau/((density1+density2)*0.01)));
				return(ret);
			} else {
				tau-=(density1+density2)*0.01;
				ret=next;
			}
			if(!IsInCloud(ret)) return(ret);
		}

		return(ret);
	}

	public double OpticalDepth() {
		int i;
		double ret=0;

		for(i=0; i<20; i++) {
			try {
				ret+=data.GetElement(i).x;
			}
			catch(DataSet.DataException e) {}
		}
		return(ret/20.0);
	}

	private double OpticalDensity(RTVector r) {
		double ret;

		try {
			ret=data.Interpolate(r.Get(2));
		}
		catch(DataSet2D.InterpolationException e) {
			return(0.0);
		}
		return(ret);
	}

	public boolean IsInCloud(RTVector r) {
		if((r.Get(2)>0.0) && (r.Get(2)<=1.0)) return(true);
		return(false);
	}

	public boolean IsBelowCloud(RTVector r) {
		if(r.Get(2)<=0.0) return(true);
		return(false);
	}

	public RTVector RandomStartLocation(RTVector dir) {
		RTVector ret=new RTVector(dir.Dimension());

		ret.Set(0,0.5);
		ret.Set(1,0.0);
		ret.Set(2,1.0);

		return(ret);
	}

	public void DrawCloud(Panel p) {
		Graphics g=p.getGraphics();
		int j;
		int edge1,edge2;
		float white;

		edge1=0;
		for(j=18; j>=0; j--) {
			edge2=p.size().height*(19-j)/19;
			try {
				white=(float)(1.0-Math.exp(-data.GetElement(j).x/20.0));
				g.setColor(new Color(white,white,1.0f));
				g.fillRect(0,edge1,p.size().width,edge2);
				edge1=edge2;
			}
			catch(DataSet.DataException e) {}
		}
	}

	public void DrawPath(Panel p,Vector v) {
		int i,x1,y1,x2,y2;
		RTVector rtv;
		Graphics g=p.getGraphics();

		g.setColor(Color.yellow);
		for(i=1; i<v.size(); i++) {
			rtv=(RTVector)v.elementAt(i-1);
			x1=(int)((rtv.Get(0)-Math.floor(rtv.Get(0)))*p.size().width);
			y1=(int)((1.0-rtv.Get(2))*p.size().height);
			rtv=(RTVector)v.elementAt(i);
			x2=(int)((rtv.Get(0)-Math.floor(rtv.Get(0)))*p.size().width);
			y2=(int)((1.0-rtv.Get(2))*p.size().height);
			g.drawLine(x1,y1,x2,y2);
		}
	}

	public DataSet2D GetData(int which) {
		if(which!=0) return(null);
		return(data);
	}

	// For the 3D Slab the data is just the density as a function of height.
	private DataSet2D data;
}