/*
 * dff7.java - revised 4 Oct 09 - width 321, height 241
 * @author jackord@kw.igs.net
 * X-ray diffraction patterns for cubic crystals generated by superimposing
 *   Huygens' wavelets from an nxnxn array of single atoms (SC) or a basis of
 *   two (BCC) or four (FCC) atoms, where n=8, 12, 16, or 20.
 * The wavelength can be chosen to enhance diffraction from
 *   (111), (201), or (211) planes.
 * The pattern from the basis is displayed first (for 2 seconds),
 *   then frames 1 to n show the development of the pattern as a row is formed,
 *   frames n+1 to 2*n as rows are added to form a layer,
 *   and finally frames 2*n+1 to 3*n as layers are added to form a cube.
 */

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

public class dff7 extends Applet 
                  implements ActionListener {
  int kk=0; int first=0;                               // Declarations
  String b1s="SC"; Button b1=new Button(b1s);
  String b2s="BCC"; Button b2=new Button(b2s);
  String b3s="FCC"; Button b3=new Button(b3s);
  Choice chla=new Choice();
  Choice chnb=new Choice();
  Choice chex=new Choice();
  Image bim;
  Graphics bgr;

  public void init() {
    setBackground(new Color(211, 211, 211));
    chla.setBackground(getBackground());
    chnb.setBackground(getBackground());
    chex.setBackground(getBackground());
    setFont(new Font("Helvetica", Font.PLAIN, 12));
    add(b1); b1.addActionListener(this);
    add(b2); b2.addActionListener(this);
    add(b3); b3.addActionListener(this);
    chla.addItem("la=2a/3"); chla.addItem("la=2a/5");
    chla.addItem("la=2a/6");
    add(chla);
    chnb.addItem("n=8"); chnb.addItem("n=12");
    chnb.addItem("n=16"); chnb.addItem("n=20");
    add(chnb);
    chex.addItem("expX1"); chex.addItem("expX10");
    chex.addItem("expX100");
    add(chex);
    chla.select(0);
    chnb.select(3);
    chex.select(0);
  }

  public void paint(Graphics g) {                      // Main Program
    if (first==0) {
      bim=createImage(241, 241);                       // Animation buffer
      bgr=bim.getGraphics();
      first=1;
    }
    b1.setBounds(20, 5, 40, 20);
    b2.setBounds(20, 30, 40, 20);
    b3.setBounds(20, 55, 40, 20);
    chla.setBounds(5, 80, 70, 20);
    chnb.setBounds(5, 105, 70, 20);
    chex.setBounds(5, 130, 70, 20);
    int c, cg, im, n, ne, ni, x0, y0, del;
    int [] nb=new int[4];
    int [] ex=new int[3];
    double a, b, d, z, zz, r0, qr, qi, rr, ri, sr, si, t, sc, sn;
    double [] la=new double[3];
    long tt;
    a=3.615E-7; x0=120; y0=120; z=30.; zz=z*z;         // Cu lattice parameter
    nb[0]=8; nb[1]=12; nb[2]=16; nb[3]=20;
    ex[0]=1; ex[1]=10; ex[2]=100;
    la[0]=2*a/3; la[1]=2*a/5; la[2]=2*a/6;
    double pi=Math.PI;
    g.setColor(Color.black);                           // Initial screen
    g.drawRect(0, 0, 320, 240);
    n=nb[chnb.getSelectedIndex()];                     // Row length
    ne=ex[chex.getSelectedIndex()];                    // Overexposure                       // Row length
    if (kk>0) {                                        // Default Simple Cubic
      for (int nf=0; nf<=3*n; nf=nf+1) {
        if ((nf==0)||(nf==n)||(nf==2*n)) { del=2000; } else { del=250; }
        bgr.setColor(Color.black);
        bgr.fillRect(0, 0, 241, 241);
        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);
            b=2*pi*a/r0/la[chla.getSelectedIndex()];
            sr=1; si=0; ni=1; sn=1.0;
            if (kk==2) {                               // Body-Centred Cubic
              t=b/2*(nx+ny+z-r0);
              rr=Math.cos(t); ri=Math.sin(t);
              qr=sr+rr*sr-ri*si; si=si+rr*si+ri*sr;
              sr=qr;
            }
            if (kk==4) {                               // Face-Centred Cubic
              t=b/2*(nx+ny);
              rr=Math.cos(t); ri=Math.sin(t);
              qr=sr+rr*sr-ri*si; qi=si+rr*si+ri*sr;
              t=b/2*(nx+z-r0);
              rr=Math.cos(t); ri=Math.sin(t);
              qr=qr+rr*sr-ri*si; qi=qi+rr*si+ri*sr;
              t=b/2*(ny+z-r0);
              rr=Math.cos(t); ri=Math.sin(t);
              qr=qr+rr*sr-ri*si; qi=qi+rr*si+ri*sr;
              sr=qr; si=qi;
            }
            if (nf>0) {
              if (nf<=n) { im=nf; } else { im=n; }
              for (int i=1; i<=im; i=i+1) {            // Array 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; sn=2*sn;
              }
            }                                  
            if (nf>n) {
              if (nf<=2*n) { im=nf-n; } else { im=n; }
              ni=1;                                    // Array Y loop
              for (int i=1; i<=im; i=i+1) {                 
                t=ni*b*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; sn=2*sn;
              }
            }
            if (nf>2*n) {
              ni=1;
              for (int i=1; i<=nf-2*n; i=i+1) {        // Array Z loop 
                t=ni*b*(z-r0);
                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; sn=2*sn;
              }
            }
            sc=ne*1000./sn/kk;                         // Intensity scale
            c=(int)((sr*sr+si*si)*sc);
            if (c>255) { c=255; }                        
            Color col=new Color(0, c, 0);
            bgr.setColor(col);
            bgr.drawLine(x0+nx, y0+ny, x0+nx, y0+ny);  // Plot intensity
          }
        }
        g.setColor(getBackground());
        g.fillRect(5, 190, 70, 48);
        g.setColor(Color.black);
        g.drawString("Frame "+nf, 10, 235);
        if (nf==0) { g.drawString("Basis", 10, 215); }
        if (nf==n) { g.drawString("Row", 10, 215); }
        if (nf==2*n) { g.drawString("Layer", 10, 215); }
        if (nf==3*n) { g.drawString("Cube", 10, 215); }
        g.drawImage(bim, 80, 0, null);
        tt=System.currentTimeMillis()+del; 
        while (tt>System.currentTimeMillis()) { }
      }
      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; }
    if (b3s.equals(tst)) { kk=4; }
    repaint();
  }
}