/* palabolic reflector fdtd 2D               */
/* coded by Ikeuchi Mitsuru   */
/* ver 0.0.1   2003.02.05     */

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class reflectorFDTD2D extends Applet
  implements ActionListener, AdjustmentListener, Runnable {

/* -------------------------------------- set global ------ */

  Button bt_reset, bt_start, bt_stop;

  Scrollbar scr,slm;

  Thread th = null;

  Dimension dim;
  Image imgOff;
  Graphics gOff;

  int sleepTime = 50;

  double scrVar = 20.0;

  int started = 1;


  double t = 0.0;
  double dt = 1.0;

  int NNx = 201;
  int NNy = 201;

  double Ez[][] = new double[NNx+1][NNy+1];
  double Hx[][] = new double[NNx+1][NNy+1];
  double Hy[][] = new double[NNx+1][NNy+1];

  int metal[][] = new int[NNx+1][NNy+1];

  double omega = Math.PI/16.0;
  double theta = 0.0;

  int dispWidth = 400;
  int dispHeight = 220;

  int NN = 201+1;
  int xpts[] = new int[NN];
  int ypts[] = new int[NN];


/* ----------------------------- applet control ------ */

  public void init() {

    resize(dispWidth+100,dispHeight);
    setBackground(Color.white);

    dim = getSize();
    imgOff = createImage(dim.width,dim.height);
    gOff = imgOff.getGraphics();

    bt_reset= new Button("reset"); add(bt_reset);
    bt_reset.addActionListener(this);

    bt_start= new Button("start"); add(bt_start);
    bt_start.addActionListener(this);
 
    bt_stop = new Button("stop");  add(bt_stop);
    bt_stop.addActionListener(this);


    slm= new Scrollbar(Scrollbar.HORIZONTAL,16,10,8,110);
    add(new Label("lambda=")); add(slm);
    slm.addAdjustmentListener(this);

    scr= new Scrollbar(Scrollbar.HORIZONTAL,20,10,0,110);
    add(new Label("height=")); add(scr);
    scr.addAdjustmentListener(this);

    setInitialCondition();
    repaint();
  }

  public void start() {
    if (th == null) {
      th = new Thread(this);
      th.start();
    }
  }

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


  public void actionPerformed(ActionEvent ev){
    if(ev.getSource() == bt_reset){
      started = 0;
      setInitialCondition();
      offPaint();
      repaint(); 
    } else if(ev.getSource() == bt_start){ 
      if (started==0) {
        started = 1;
      } else if (started==1) {
        theta = 0.0;
      }
      offPaint();
      repaint();
    } else if(ev.getSource() == bt_stop){
      started = 0;
    }
		}


  public void adjustmentValueChanged(AdjustmentEvent ev){
    if(ev.getSource() == slm) { 
      omega = Math.PI/((double)slm.getValue());
      repaint();
    } else if(ev.getSource() == scr) { 
      scrVar = 1.0*(double)(scr.getValue());
      repaint();
    }
  }

  public void run() {
    while (th != null) {
      try {
        timeEvolution();
        offPaint();
        repaint();
        Thread.sleep(sleepTime);
      } catch (InterruptedException e) { }
    }
  }

  public void update(Graphics g) {
    paint(g);
  }

  public void paint(Graphics g) {
    g.drawImage(imgOff,0,0,this);
  }

/* ----------------------------- offPaint -------------------- */

  void offPaint() {
    int i,j;

    gOff.setColor(Color.white);
    gOff.fillRect(0,0,dim.width,dim.height);

    gOff.setColor(Color.green);
    for(j=0; j<NN; j += 8) {
      for (i=0; i<NN; i++) {     
        xpts[i] = 2*i-j/2+100;
        ypts[i] = 100-(int)(scrVar*Ez[i][j]+10*metal[i][j])+j/2;
      }
      for (i=0; i<NN-2; i++) { 
        gOff.drawLine(xpts[i],ypts[i],xpts[i+1],ypts[i+1]);
      }
    }
    for(i=0; i<NN; i += 8) {
      for (j=0; j<NN; j++) {     
        xpts[j] = 2*i-j/2+100;
        ypts[j] = 100-(int)(scrVar*Ez[i][j]+10*metal[i][j])+j/2;
      }
      for (j=0; j<NN-2; j++) { 
        gOff.drawLine(xpts[j],ypts[j],xpts[j+1],ypts[j+1]);
      }
    }

    gOff.setColor(Color.black);
    gOff.drawString("lambda="+Math.floor(Math.PI/omega)+" ",400,50);
    gOff.drawString("t="+(int)(t)+" ",400,70);
  }

/* ----------------------------- set initial condition ------ */

  void setInitialCondition() {

    t = 0.0;
    theta = 0.0;
    setMetal();
    clearField();

  }

/* ----------------------------- timeEvolution -------------- */

  void timeEvolution() {
    if (started==1) {
      fdtd2D();
    }
  }

/* ----------------------------- fdtd method 2D -------------- */

  void clearField() {
    int i,j;

    for(i=0;i<NNx+1;i++) {
      for(j=0;j<NNy+1;j++) {
       	Ez[i][j] = 0.0;
       	Hx[i][j] = 0.0;
       	Hy[i][j] = 0.0;
      }
    }
  }

  void setMetal() {
    int i,j;

    for(i=0;i<NNx;i++) {
      for(j=0;j<NNy;j++) {
       	if((double)i-190.0>-0.005*(j-100)*(j-100)) {
	         metal[i][j] = 1;
        }
      }
    }
/*
    for(i=97;i<104;i++) {
      for(j=0;j<64;j++) {
       	metal[i][j]=1;
      }
      for(j=80;j<120;j++) {
       	metal[i][j]=1;
      }
      for(j=136;j<NNy+1;j++) {
       	metal[i][j]=1;
      }
    }
*/
  }

  void fdtd2D() {
    t = t + dt;

    EzEvolution();
    EzGenerator();
    HxyEvolution();
  }

  void EzGenerator() {
    int j;
    double Ezt;

    theta += omega*dt;
    Ezt = Math.sin(theta);
    if (theta<3.1416) {
      for(j=0;j<NNy;j++) {
        Ez[0][j]=Ezt;
      }
    }

  }

  void EzEvolution() {
    int i,j;
    double sqrt2v2;

    sqrt2v2 = 0.70710678;

    for(i=0;i<NNx;i++) {
      for(j=0;j<NNy;j++) {
       	if(metal[i][j]==0) {
	         Ez[i][j] += sqrt2v2*((Hy[i+1][j]-Hy[i][j])-(Hx[i][j+1]-Hx[i][j]));
        }
      }
    }
  }


  void HxyEvolution() {
    int i,j;
    double sqrt2v2,c;

    sqrt2v2 = 0.70710678;
    c = (1.0-sqrt2v2)/(1.0+sqrt2v2);

    for(i=0; i<NNx; i++) {
      Hx[i][0] = c*Hx[i][0] + Hx[i][1];
    }
    for(i=0; i<NNx; i++) {
      Hx[i][NNy] = c*Hx[i][NNy] + Hx[i][NNy-1];
    }
    for(j=0; j<NNy; j++) {
      Hy[0][j] = c*Hy[0][j] + Hy[1][j];
    }
    for(j=0; j<NNy; j++) {
      Hy[NNx][j] = c*Hy[NNx][j] + Hy[NNx-1][j];
    }

    for(i=0;i<NNx;i++) {
      for(j=1;j<NNy;j++) {
	       Hx[i][j] -= sqrt2v2*(Ez[i][j]-Ez[i][j-1]);
      }
    }
    for(i=1;i<NNx;i++) {
      for(j=0;j<NNy;j++) {
	       Hy[i][j] += sqrt2v2*(Ez[i][j]-Ez[i-1][j]);
      }
    }

    for(i=0;i<NNx;i++) {
      Hx[i][0] -= c*Hx[i][1];
    }
    for(i=0;i<NNx;i++) {
      Hx[i][NNy] -= c*Hx[i][NNy-1];
    }
    for(j=0;j<NNy;j++) {
      Hy[0][j] -= c*Hy[1][j];
    }
    for(j=0;j<NNy;j++) {
      Hy[NNx][j] -= c*Hy[NNx-1][j];
    }
  }

/* ----------------------------- end of applet -------------- */

}