// FILE:     RayTrace.java
// PURPOSE:  An applet to display our ray tracing environment.
//
// MODS:     11.25.98 -- Leonard McMillan -- original 
//           11.25.98 -- jlueck@mit.edu   -- Rev 2

import java.applet.*;
import java.awt.*;
import java.io.*;
import java.net.*;
import java.util.*;

/***************************************************
*
*   An instructional Ray-Tracing Renderer written
*   for MIT 6.837  Fall '98 by Leonard McMillan.
*
*   A fairly primitive Ray-Tracing program written
*   on a Sunday afternoon before Monday's class.
*   Everything is contained in a single file. The
*   structure should be fairly easy to extend, with
*   new primitives, features and other such stuff.
*
*   I tend to write things bottom up (old K&R C
*   habits die slowly). If you want the big picture
*   scroll to the applet code at the end and work
*   your way back here.
*
****************************************************/
public class RayTrace extends Applet implements Runnable, LightConsts {

    final static int CHUNKSIZE = 100;
    Image screen;
    Graphics gc;
    Vector objectList;
    Vector lightList;
    Surface currentSurface;
    
    Vector3D eye, lookat, up;
    Vector3D Du, Dv, Vp;
    float fov;
    
    Color background;
    
    int width, height;

    public void init( ) {
        // initialize the off-screen rendering buffer
        width = size().width;
        height = size().height;
        screen = createImage(width, height);
        gc = screen.getGraphics();
        gc.setColor(getBackground());
        gc.fillRect(0, 0, width, height);

        fov = 30;               // default horizonal field of view

        // Initialize various lists
        objectList = new Vector(CHUNKSIZE, CHUNKSIZE);
        lightList = new Vector(CHUNKSIZE, CHUNKSIZE);
        currentSurface = new Surface(0.8f, 0.2f, 0.9f, 
				     0.2f, 0.4f, 0.4f, 
				     10.0f, 0f, 0f, 1f);

        // Parse the scene file
        String filename = getParameter("datafile");
        showStatus("Parsing " + filename);
        InputStream is = null;
        try {
            is = new URL(getDocumentBase(), filename).openStream();
            ReadInput(is);
            is.close();
        } catch (IOException e) {
            showStatus("Error reading "+filename);
            System.err.println("Error reading "+filename);
            System.exit(-1);
        }

        // Initialize more defaults if they weren't specified
        if (eye == null) eye = new Vector3D(0, 0, 10);
        if (lookat == null) lookat = new Vector3D(0, 0, 0);
        if (up  == null) up = new Vector3D(0, 1, 0);
        if (background == null) background = new Color(0,0,0);

        // Compute viewing matrix that maps a
        // screen coordinate to a ray direction
        Vector3D look = new Vector3D(lookat.x - eye.x, 
				     lookat.y - eye.y, 
				     lookat.z - eye.z);
        Du = Vector3D.normalize(look.cross(up));
        Dv = Vector3D.normalize(look.cross(Du));
        float fl = (float)(width / (2*Math.tan((0.5*fov)*Math.PI/180)));
        Vp = Vector3D.normalize(look);
        Vp.x = Vp.x*fl - 0.5f*(width*Du.x + height*Dv.x);
        Vp.y = Vp.y*fl - 0.5f*(width*Du.y + height*Dv.y);
        Vp.z = Vp.z*fl - 0.5f*(width*Du.z + height*Dv.z);
    }


    double getNumber(StreamTokenizer st) throws IOException {
	if (st.nextToken() != StreamTokenizer.TT_NUMBER) {
	    System.err.println("ERROR: number expected in line " + 
			       st.lineno());
	    throw new IOException(st.toString());
	}
	return st.nval;
    }

    void ReadInput(InputStream is) throws IOException {
	StreamTokenizer st = new StreamTokenizer(is);
	st.commentChar('#');
    scan: while (true) {
	switch (st.nextToken()) {
	default:
	    break scan;
	case StreamTokenizer.TT_WORD:
	    if (st.sval.equals("sphere")) {
		Vector3D v = new Vector3D((float) getNumber(st), 
					  (float) getNumber(st), 
					  (float) getNumber(st));
		float r = (float) getNumber(st);
		objectList.addElement(new Sphere(currentSurface, v, r));
	    } else if (st.sval.equals("triangle")) {
		Vector3D v1 = new Vector3D((float) getNumber(st), 
					   (float) getNumber(st), 
					   (float) getNumber(st));
		Vector3D v2 = new Vector3D((float) getNumber(st), 
					   (float) getNumber(st), 
					   (float) getNumber(st));
		Vector3D v3 = new Vector3D((float) getNumber(st), 
					   (float) getNumber(st), 
					   (float) getNumber(st));
		objectList.addElement(new Triangle(currentSurface,v1,v2,v3));
	    } else if (st.sval.equals("eye")) {
		eye = new Vector3D((float) getNumber(st), 
				   (float) getNumber(st), 
				   (float) getNumber(st));
	    } else if (st.sval.equals("lookat")) {
		lookat = new Vector3D((float) getNumber(st), 
				      (float) getNumber(st), 
				      (float) getNumber(st));
	    } else if (st.sval.equals("up")) {
		up = new Vector3D((float) getNumber(st), 
				  (float) getNumber(st), 
				  (float) getNumber(st));
	    } else if (st.sval.equals("fov")) {
		fov = (float) getNumber(st);
	    } else if (st.sval.equals("background")) {
		background = new Color((float) getNumber(st), 
				       (float) getNumber(st), 
				       (float) getNumber(st));
	    } else if (st.sval.equals("light")) {
		float r = (float) getNumber(st);
		float g = (float) getNumber(st);
		float b = (float) getNumber(st);
		if (st.nextToken() != StreamTokenizer.TT_WORD) {
		    throw new IOException(st.toString());
		}
		if (st.sval.equals("ambient")) {
		    lightList.addElement(new Light(AMBIENT, null, r, g, b));
		} else if (st.sval.equals("directional")) {
		    Vector3D v = new Vector3D((float) getNumber(st), 
					      (float) getNumber(st), 
					      (float) getNumber(st));
		    lightList.addElement(new Light(DIRECTIONAL, v, r, g, b));
		} else if (st.sval.equals("point")) {
		    Vector3D v = new Vector3D((float) getNumber(st), 
					      (float) getNumber(st), 
					      (float) getNumber(st));
		    lightList.addElement(new Light(POINT, v, r, g, b));
		} else {
		    System.err.println("ERROR: in line " + st.lineno()+
				       " at " + st.sval);
		    throw new IOException(st.toString());
		}
	    } else if (st.sval.equals("surface")) {
		float r = (float) getNumber(st);
		float g = (float) getNumber(st);
		float b = (float) getNumber(st);
		float ka = (float) getNumber(st);
		float kd = (float) getNumber(st);
		float ks = (float) getNumber(st);
		float ns = (float) getNumber(st);
		float kr = (float) getNumber(st);
		float kt = (float) getNumber(st);
		float index = (float) getNumber(st);
		currentSurface = new Surface(r, g, b, 
					     ka, kd, ks, ns, 
					     kr, kt, index);
	    }
	    break;
	}
    }
    is.close();
    if (st.ttype != StreamTokenizer.TT_EOF)
	throw new IOException(st.toString());
    }
    
    boolean finished = false;
    
    public void paint(Graphics g) {
        if (finished)
            g.drawImage(screen, 0, 0, this);
    }

    // this overide avoid the unnecessary clear on each paint()
    public void update(Graphics g) {
        paint(g);
    }


    private Thread raytracer;

    public void start() {
        if (raytracer == null) {
            raytracer = new Thread(this);
            raytracer.start();
        } else {
            raytracer.resume();
        }
    }

    public void stop() {
        if (raytracer != null) {
            raytracer.suspend();
        }
    }

    private void renderPixel(int i, int j) {
        Vector3D dir = new Vector3D(i*Du.x + j*Dv.x + Vp.x,
				    i*Du.y + j*Dv.y + Vp.y,
				    i*Du.z + j*Dv.z + Vp.z);
        Ray ray = new Ray(eye, dir);
        if (ray.trace(objectList)) {
            gc.setColor(ray.Shade(lightList, objectList, background));
        } else {
            gc.setColor(background);
        }
        gc.drawLine(i, j, i, j);        // oh well, it works.
    }

    public void run() {
        Graphics g = getGraphics();
        long time = System.currentTimeMillis();
        for (int j = 0; j < height; j++) {
            //showStatus("Scanline "+j);
            for (int i = 0; i < width; i++) {
                renderPixel(i, j);
            }
	    // doing this less often speed things up a bit
            g.drawImage(screen, 0, 0, this);        
        }
        g.drawImage(screen, 0, 0, this);
        time = System.currentTimeMillis() - time;
        showStatus("Rendered in "+(time/60000)+":"+((time%60000)*0.001));
        finished = true;
    }


    public boolean mouseDown(Event e, int x, int y) {
        renderPixel(x, y);
        repaint();
        return true;
    }

    public boolean mouseDrag(Event e, int x, int y) {
        renderPixel(x, y);
        repaint();
        return true;
    }

    public boolean mouseUp(Event e, int x, int y) {
        renderPixel(x, y);
        repaint();
        return true;
    }
}