/* scatter FDTD 2D           */
/* coded by Ikeuchi Mitsuru  */
/* ver 0.0.1   2004.02.14    */
/* ver 0.0.2   2004.05.15  bug fixed */

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

public class scatterFDTD2D extends Applet
  implements MouseListener, MouseMotionListener,
    ItemListener, ActionListener, AdjustmentListener, Runnable {

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

  Choice cm1,cvw;
  Button bt_reset, bt_start, bt_stop;
  Scrollbar scr,slm;

  Thread th = null;

  Dimension dim;
  Image imgOff;
  Graphics gOff;

  int sleepTime = 50;

  int dispMode = 0;
  int scatterer = 2;
  int started = 1;
  double magn = 1.0;
  double omega = Math.PI/32.0;
  double theta = 0.0;


  double t = 0.0;
  double dt = 1.0;

  int NNx = 241;
  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];

  double ep[][] = new double[NNx+1][NNy+1];
  double mu[][] = new double[NNx+1][NNy+1];
  double sg[][] = new double[NNx+1][NNy+1];
  int metal[][] = new int[NNx+1][NNy+1];

  double cr[][] = new double[NNx+1][NNy+1];

  int dgX, dgY, dgXb,dgYb;

  double viewTheta = -15.0*3.14/180.0;
  double viewFai = -72.0*3.14/180.0;
  double dtheta = 0.0*3.14/180.0;
  double pai = 3.1415926536;

  double cosTh = Math.cos(viewTheta); 
  double sinTh = Math.sin(viewTheta);
  double cosFi = Math.cos(viewFai);
  double sinFi = Math.sin(viewFai);

  int NN = NNx+NNy+2;
  int xpts[] = new int[NN];
  int ypts[] = new int[NN];

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

  public void init() {

    resize(630,300);
    setBackground(Color.white);

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

    cm1 = new Choice();
    cm1.addItem("vacuum"); cm1.addItem("metal");
    cm1.addItem("dielectrics"); cm1.addItem("ferro-mag");
    cm1.addItem("resistor");
    cm1.addItemListener(this);
    cm1.select("dielectrics");

    cvw = new Choice();
    cvw.addItem("Ez wave"); cvw.addItem("Hxy line");
    cvw.addItemListener(this);

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

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

    addMouseListener(this);  
    addMouseMotionListener(this);

    slm= new Scrollbar(Scrollbar.HORIZONTAL,32,10,8,74);
    slm.addAdjustmentListener(this);

    setLayout(new BorderLayout());
    Panel pnl = new Panel();
    pnl.setLayout(new GridLayout(1,6,5,0));
    pnl.add(bt_reset);
    pnl.add(bt_start);
    pnl.add(bt_stop);
    pnl.add(slm);
    pnl.add(cm1);
    pnl.add(cvw);
    add(pnl,"North");

    setInitialCondition();
  }

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

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


  public void itemStateChanged(ItemEvent ev){
    if (ev.getSource() == cm1){
      scatterer = cm1.getSelectedIndex();
      setInitialCondition();
    } else if (ev.getSource() == cvw){
      dispMode = cvw.getSelectedIndex();
    }
  }

  public void actionPerformed(ActionEvent ev){
    if(ev.getSource() == bt_reset){
      started = 0;
      setInitialCondition();
    } 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());
    } else if(ev.getSource() == scr) { 
      magn = 0.01*(double)(scr.getValue());
    }
  }

  public void mousePressed(MouseEvent ev){ }
  public void mouseReleased(MouseEvent ev){
    dgXb = 0; dgYb = 0;
    dgX = 0; dgY = 0;
  }
  public void mouseClicked(MouseEvent ev){ }
  public void mouseEntered(MouseEvent ev){ } 
  public void mouseExited (MouseEvent ev){ }

  public void mouseMoved  (MouseEvent ev){ }

  public void mouseDragged(MouseEvent ev){
    dgXb = dgX; dgYb = dgY;
    dgX=ev.getX();
    dgY=ev.getY();
    if (dgXb==0 && dgYb==0) {
      dgXb = dgX; dgYb = dgY;
    }
    viewTheta += 0.5*3.14/180.0*(dgX-dgXb);
    viewFai += 0.5*3.14/180.0*(dgY-dgYb);
    cosTh = Math.cos(viewTheta); 
    sinTh = Math.sin(viewTheta);
    cosFi = Math.cos(viewFai);
    sinFi = Math.sin(viewFai);
  }


  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;
    int cx,cy,cz,gbx,gby,gb;
    double z,px,py,pz,sc,scrVar;

    cx = NNx/2;
    cy = NNy/2;
    cz = 0;
    sc = 2.0;
    scrVar = 15.0*magn;

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


    if (dispMode==0) {

      gbx = 10+(int)(cx/sc);
      gby = -80+(int)(cy/sc);
      for(j=0; j<NNy; j += 8) {
        for (i=0; i<NNx; i++) { 
          z = scrVar*Ez[i][j]+cz;
          py = cosFi*(j-cy)+sinFi*(z-cz) + cy; 
          pz = -sinFi*(j-cy)+cosFi*(z-cz) + cz;
          px = cosTh*(i-cx)+sinTh*(pz-cz) + cx; 
          pz = -sinTh*(i-cx)+cosTh*(pz-cz) + cz;
          xpts[i] = (int)(sc*px)+gbx;
          ypts[i] = (int)(sc*py)+gby;
        }
        for (i=0; i<NNx-2; i++) {
          if (sg[i][j]>0.0) {
            gOff.setColor(Color.getHSBColor((float)cr[i][j],0.9f,0.5f));
          } else {
            gOff.setColor(Color.getHSBColor((float)cr[i][j],0.9f,0.9f));
          }
          gOff.drawLine(xpts[i],ypts[i],xpts[i+1],ypts[i+1]);
        }
      }

      for(i=0; i<NNx; i += 8) {
        for (j=0; j<NNy; j++) { 
          z = scrVar*Ez[i][j]+cz;
          py = cosFi*(j-cy)+sinFi*(z-cz) + cy; 
          pz = -sinFi*(j-cy)+cosFi*(z-cz) + cz;
          px = cosTh*(i-cx)+sinTh*(pz-cz) + cx; 
          pz = -sinTh*(i-cx)+cosTh*(pz-cz) + cz;
          xpts[j] = (int)(sc*px)+gbx;
          ypts[j] = (int)(sc*py)+gby;
        }
        for (j=0; j<NNy-2; j++) { 
          if (sg[i][j]>0.0) {
            gOff.setColor(Color.getHSBColor((float)cr[i][j],0.9f,0.5f));
          } else {
            gOff.setColor(Color.getHSBColor((float)cr[i][j],0.9f,0.9f));
          }
          gOff.drawLine(xpts[j],ypts[j],xpts[j+1],ypts[j+1]);
        }
      }

    } else if (dispMode==1) {

      gOff.setColor(Color.green);
      for(j=0; j<NNy; j += 4) {
        for (i=0; i<NNx; i += 4) { 
          gOff.setColor(Color.getHSBColor( (float)cr[i][j],
            (float)(0.3+0.6/(30.0*sg[i][j]+1.0)),(float)(0.5+0.25*Ez[i][j])));
          gOff.fillRect(i+30,j+50,4,4);
        }
      }

      gOff.setColor(Color.red);
      for(j=0; j<NNy-2; j += 8) {
        for (i=0; i<NNx-2; i += 8) { 
          gOff.drawLine(i+34,j+54,i+34+(int)(scrVar*Hx[i][j]),j+54+(int)(scrVar*Hy[i][j]));
        }
      }
    }

    gOff.setColor(Color.blue);
    gOff.drawString("t="+(int)(t)+" ",630/6*0+10,40);

    gOff.setColor(Color.black);
    gOff.drawString("lambda="+Math.floor(Math.PI/omega)+" ",630/6*3+10,40);
    gOff.drawString("material",630/6*4+10,40);
    gOff.drawString("view",630/6*5+10,40);

  }

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

  void setInitialCondition() {

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

  }

  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 setMaterial() {
    int i,j;

    for(i=0;i<NNx+1;i++) {
      for(j=0;j<NNy+1;j++) {
       	ep[i][j] = 1.0;
       	mu[i][j] = 1.0;
       	sg[i][j] = 0.0;
       	metal[i][j] = 0;
      }
    }

    for(i=80;i<180;i++) {
      for(j=50;j<150;j++) {
       	if (scatterer==1) {
         	metal[i][j] = 1;
        }
       	if (scatterer==2) {
         	ep[i][j] = 4.0;
        }
       	if (scatterer==3) {
         	mu[i][j] = 4.0;
        }
       	if (scatterer==4) {
         	sg[i][j] = 0.05;
        }
      }
    }
    setcolor();
  }

  void setcolor() {
    int i,j;
    double c;

    for(i=0;i<NNx+1;i++) {
      for(j=0;j<NNy+1;j++) {
        c = 0.33;
        if (metal[i][j]==0) {
          c = 0.33;
         	if (ep[i][j]>1.0) {
            if (mu[i][j]>1.0) {
           	  c = 0.85;
            } else {
              c = 0.08;
            }
          } else {
            if (mu[i][j]>1.0) {
         	    c = 0.66;
            }
          }
          if (sg[i][j]>0.0) {
            c = c-0.05;
          }
        } else {
          c = 0.15;
        }
        cr[i][j] = c;
      }
    }
  }


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

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

  void fdtd2D() {

    t = t + 0.5*dt;
    EzEvolution();
    EzGenerator();
    HxyEvolution();
  }

  void EzGenerator() {
    int j;
    double Ezt;

    theta += omega*0.5*dt;
    Ezt = Math.sin(theta);
    if (theta<3.1416*2.0) {
      for(j=0;j<NNy;j++) {
        Ez[0][j]=Ezt;
      }
    }

  }

  void EzEvolution() {
    int i,j;
    double sqrt2v2,d2;

    sqrt2v2 = 0.707*0.5;
    d2 = dt*0.5;

    for(i=0;i<NNx;i++) {
      for(j=0;j<NNy;j++) {
        if (metal[i][j]==0) {
         	Ez[i][j] += (-sg[i][j]*d2*Ez[i][j] + 
            (sqrt2v2/ep[i][j])*((Hy[i+1][j]-Hy[i][j])-(Hx[i][j+1]-Hx[i][j])));
        }
      }
    }
  }


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

    sqrt2v2 = 0.707*0.5;
    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/mu[i][j]*(Ez[i][j]-Ez[i][j-1]);
      }
    }

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

}