/*
 * dif4x.java - revised 31 Jan 07 - width 301, height 241
 * @author jackord@kw.igs.net
 * The diffraction pattern from an array in the form of a cube
 *   or close-packed rhomb
 * The 41x41 2-D arrays can be assembled into stacks of 1, 3, 11, or 41
 *   layers (41 layers are required to make a complete cube or rhomb)
 * Wavelengths are chosen to enhance diffraction from (111) planes in the
 *   simple cube and from (200) planes in the rhomb (fcc lattice)
 *
 */

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

public class dif4x extends Applet 
                  implements ActionListener {
  int kk=0; int first=0;                               // Declarations
  String b1s="Cube"; Button b1=new Button(b1s);
  String b2s="Rhomb"; Button b2=new Button(b2s);
  Choice chnp=new Choice();

  public void init() {
    add(b1); b1.addActionListener(this);
    add(b2); b2.addActionListener(this);
    setBackground(new Color(211, 211, 211));
    chnp.setBackground(getBackground());
    setFont(new Font("Helvetica", Font.PLAIN, 12));
    chnp.addItem("N=1"); chnp.addItem("N=3");
    chnp.addItem("N=11"); chnp.addItem("N=41");
    add(chnp);
    chnp.select(0);
  }

  public void paint(Graphics g) {                      // Main Program
    if (first==0) {
      b1.setBounds(5, 5, 50, 20);
      b2.setBounds(5, 30, 50, 20);
      chnp.setBounds(3, 55, 57, 4);
      first=1;
    }
    double b, by, dd, z, zz, la, r0, qr, qi, rr, ri, sr, si, t, sc;
    int c, n, nm, np, x0, y0;
    int [] nl=new int[4];
    nl[0]=0; nl[1]=1; nl[2]=5; nl[3]=20;
    np=nl[chnp.getSelectedIndex()];
    double pi=Math.PI;
    g.setColor(Color.black);                           // Initial screen
    g.drawRect(0, 0, 300, 240);
    n=20;                                              // 41x41 2-D array
    dd=2.55E-7; x0=180; y0=120; z=30.; zz=z*z; 
    long tt=System.currentTimeMillis();
    if (kk==1) {                                       // Cube
      nm=(2*n+1)*(2*n+1)*(2*np+1); sc=255000./nm/nm;
      la=2*dd/3;
      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); sr=0; si=0;    
          b=2*pi*dd/r0/la;
          for (int i=-n; i<=n; i=i+1) {                // X loop Algorithm D
            t=b*i*nx; 
            sr=sr+Math.cos(t); si=si+Math.sin(t);
          }
          qr=sr; qi=si;
          for (int i=-n; i<=n; i=i+1) {                // Y loop Algorithm D
            if (i==0) { i=i+1; }
            rr=Math.cos(i*b*ny); ri=Math.sin(i*b*ny);
            qr=qr+rr*sr-ri*si; qi=qi+rr*si+ri*sr;
          }

          if (np>0) {
            sr=qr; si=qi;
            for (int i=-np; i<=np; i=i+1) {            // Z loop Algorithm D
              if (i==0) { i=i+1; }
              rr=Math.cos(i*b*(z-r0)); ri=Math.sin(i*b*(z-r0));
              qr=qr+rr*sr-ri*si; qi=qi+rr*si+ri*sr;
            }
          }
          c=(int)((qr*qr+qi*qi)*sc);              
          if (c>255) { c=255; }                        
          Color col=new Color(c, 0, 0);
          g.setColor(col);
          g.drawLine(x0+nx, y0+ny, x0+nx, y0+ny);      // Plot intensity
          g.drawLine(x0-nx, y0+ny, x0-nx, y0+ny);      // assuming symmetry
          g.drawLine(x0+nx, y0-ny, x0+nx, y0-ny);        
          g.drawLine(x0-nx, y0-ny, x0-nx, y0-ny);        
        }
      }
      g.setColor(Color.black);                         
      g.drawString(""+(System.currentTimeMillis()-tt)+" ms", 5, 235);
    }
    if (kk==2) {                                       // Close-packed Rhomb 
      nm=(2*n+1)*(2*n+1)*(2*np+1); sc=255000./nm/nm;       
      la=.8165*dd;
      for (int ny=-119; ny<=119; ny=ny+1) {            // Screen Y loop
        for (int nx=-119; nx<=119; nx=nx+1) {          // Screen X loop
          r0=Math.sqrt(zz+nx*nx+ny*ny); sr=0; si=0; 
          b=2*pi*dd/r0/la;
          by=b*Math.sqrt(3)/2;                         
          for (int i=-n; i<=n; i=i+1) {                // X loop Algorithm D
            t=b*i*nx; 
            sr=sr+Math.cos(t); si=si+Math.sin(t);
          }
          qr=sr; qi=si;
          for (int i=-n; i<=n; i=i+1) {                // Y loop Algorithm D
            if (i==0) { i=i+1; }
            t=i*b*nx/2+i*by*ny;
            rr=Math.cos(t); ri=Math.sin(t);
            qr=qr+rr*sr-ri*si; qi=qi+rr*si+ri*sr;
          }
          if (np>0) {
            sr=qr; si=qi;
            for (int i=-np; i<=np; i=i+1) {            // Z loop Algorithm D
              if (i==0) { i=i+1; }
              t=i*b*nx/2+i*by*ny/3+i*b*(z-r0)/Math.sqrt(1.5);
              rr=Math.cos(t); ri=Math.sin(t);
              qr=qr+rr*sr-ri*si; qi=qi+rr*si+ri*sr;
            }
          }
          c=(int)((qr*qr+qi*qi)*sc);              
          if (c>255) { c=255; }                        
          Color col=new Color(c, 0, 0);
          g.setColor(col);
          g.drawLine(x0+nx, y0-ny, x0+nx, y0-ny);      // Plot intensity
        }
      }
      g.setColor(Color.black);                         
      g.drawString(""+(System.currentTimeMillis()-tt)+" ms", 5, 235);
    }
    kk=0;
  }

  public void actionPerformed(ActionEvent e) {         // Buttons
    String tst;
    tst=e.getActionCommand();
    if (b1s.equals(tst)) { kk=1; }
    if (b2s.equals(tst)) { kk=2; }
    repaint();
  }
}