/*
 * df3.java - revised 4 Feb 10 - width 286, height 241
 * @author jackord@kw.igs.net
 * The diffraction pattern produced when light from a helium-neon laser
 *   strikes either
 *   (1) an equilateral triangular aperture (side d=.05 mm),
 *   (2) a rectangular aperture (.05x.025 mm), or
 *   (3) a square aperture (side .05 mm)
 *   and falls on a
 *   screen 1000 mm away (125 mm if "z/8" is chosen for the triangle).
 * One pixel represents 1 mm on the screen.
 * The numerical calculation uses
 *   (1) a close-packed array for the triangle with 50 points along d
 *       (25 if "n/2" is chosen)
 *   (2) a square 1024x512 grid for the rectangle
 *   (3) a square 1024x1024 grid for the square.
 * The rectangle and square use the fast algorithm.
 * The plot is "overexposed" to make lower intensity variations visible.
 */

import java.applet.Applet;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class df3 extends Applet 
                  implements ActionListener {
  int kk=0;                                            // Declarations
  String bb1s="Tri"; Button bb1=new Button(bb1s);
  String bb2s="Rct"; Button bb2=new Button(bb2s);
  String bb3s="Sqr"; Button bb3=new Button(bb3s);
  Checkbox ch1=new Checkbox("n/2");
  Checkbox ch2=new Checkbox("z/8");

  public void init() {
    add(bb1); bb1.addActionListener(this);
    add(ch1); add(ch2);
    add(bb2); bb2.addActionListener(this);
    add(bb3); bb3.addActionListener(this);
    setBackground(new Color(211, 211, 211));
    ch1.setBackground(getBackground());
    ch2.setBackground(getBackground());
  }

  public void paint(Graphics g) {                      // Main Program
    bb1.setBounds(3, 5, 35, 20);
    ch1.setBounds(3, 30, 35, 20);
    ch2.setBounds(3, 55, 35, 20);
    bb2.setBounds(3, 80, 35, 20);
    bb3.setBounds(3, 105, 35, 20);
    double la=.633/1000;                               // Helium-neon red
    double b, by, d, dd, z, zz, a, r0, qr, qi, rr, ri, sr, si, t, sc;
    int c, n, nb, ni, nm, x0, y0;
    double pi=Math.PI;
    g.setColor(Color.black);                           // Initial screen
    g.drawRect(0, 0, 280, 240);
    d=.05; x0=160; y0=120;
    long tt=System.currentTimeMillis();
    if (kk==1) {
      if (ch1.getState()==true) { n=25; } else { n=50; }
      if (ch2.getState()==true) { z=125; } else { z=1000; }
      dd=d/n;  zz=z*z; 
      nm=n*(n+1)/2; sc=255000./nm/nm;              
      for (int ny=-120; ny<=120; ny=ny+1) {            // Screen Y loop
        for (int nx=0; nx<=120; nx=nx+1) {             // Screen X loop
          r0=Math.sqrt(zz+nx*nx+ny*ny); sr=0; si=0;
          a=.5*(1+z/r0)*z/r0; b=2*pi*dd/r0/la;
          by=b*Math.sqrt(3)/2;                         // Close-packed array
          for (int j=0; j<(n-1); j=j+1) {              // Aperture Y loop
            for (int i=1; i<=n-j; i=i+1) {             // Aperture X loop
              t=b*nx*(i+.5*j)+by*ny*j; 
              sr=sr+Math.cos(t); si=si+Math.sin(t);
            }
          }
          c=(int)((sr*sr+si*si)*a*a*sc);               // Overexpose 
          if (c>255) { c=255; }                        // and cut off max
          Color col=new Color(c, 0, 0);
          g.setColor(col);
          g.drawLine(x0+nx, y0-ny, x0+nx, y0-ny);      // Plot pattern
          g.drawLine(x0-nx, y0-ny, x0-nx, y0-ny);      // assming x symmetry
        }
      }
      g.setColor(Color.white);                         // Show
      g.drawLine(x0-20, y0+12, x0+20, y0+12);          // aperture orientation
      g.drawLine(x0+20, y0+12, x0, y0-24);
      g.drawLine(x0, y0-24, x0-20, y0+12);
      g.drawString(""+(System.currentTimeMillis()-tt)+" ms", 42, 235);
    }
    if (kk>1) {
      ch1.setState(false);
      ch2.setState(false);
      nb=10; n=1024; dd=d/n; z=1000.; zz=z*z;
      sc=255000./n/n/n/n; if (kk==2 ) { sc=sc*4; }
      for (int ny=0; ny<=119; ny=ny+1) {               // Screen Y loop
        for (int nx=0; nx<=119; nx=nx+1) {             // Screen X loop
          r0=Math.sqrt(zz+nx*nx+ny*ny);
          a=.5*(1+z/r0)*z/r0; b=2*pi*dd/r0/la;
          sr=1; si=0; ni=1;
          for (int i=1; i<=nb; i=i+1) {                // Aperture X loop
            t=b*ni*nx;
            rr=Math.cos(t); ri=Math.sin(t);
            qr=sr+rr*sr-ri*si; si=si+rr*si+ri*sr;
            sr=qr; ni=2*ni;
          }
          ni=1;                                        // Aperture Y loop
          for (int i=1; i<=nb-1+(int)((kk-1)/2); i=i+1) {                 
            t=b*ni*ny;                   
            rr=Math.cos(t); ri=Math.sin(t);
            qr=sr+rr*sr-ri*si; si=si+rr*si+ri*sr;
            sr=qr; ni=2*ni;
          }
          c=(int)((sr*sr+si*si)*a*a*sc);
          if (c>255) { c=255; }                        // Overexpose
          Color col=new Color(c, 0, 0);
          g.setColor(col);
          g.drawLine(x0+nx, y0+ny, x0+nx, y0+ny);      // Plot pattern
          g.drawLine(x0+nx, y0-ny, x0+nx, y0-ny);      // Plot pattern
          g.drawLine(x0-nx, y0+ny, x0-nx, y0+ny);      // Plot pattern
          g.drawLine(x0-nx, y0-ny, x0-nx, y0-ny);      // Plot pattern
        }
      }
      g.setColor(Color.white);                         // Show
      if (kk==2) { g.drawRect(x0-20, y0-10, 40, 20); } // Rectangle orientation
      else { g.drawRect(x0-20, y0-20, 40, 40); }       // Square orientation
      g.drawString(""+(System.currentTimeMillis()-tt)+" ms", 42, 235);
    }
    kk=0;
  }

  public void actionPerformed(ActionEvent e) {         // Buttons
    String tst;
    tst=e.getActionCommand();
    if (bb1s.equals(tst)) { kk=1; }
    if (bb2s.equals(tst)) { kk=2; }
    if (bb3s.equals(tst)) { kk=3; }
    repaint();
  }
}