// 3D random landscape,  Evgeny Demidov  19 Feb 2002
  import java.awt.*;
  import java.awt.event.*;
  import java.util.StringTokenizer;
  public class applet-math-random3D extends java.applet.Applet
   implements ItemListener, ActionListener, MouseListener, MouseMotionListener{
    int n = 32, n1, Rc = 4, h,w,h2,w2, mx0,my0,  xPol[],yPol[], iCol[][][];
    double Vp = 0, Vs, Vmin, Vmax,
     fiX = .8, fiY = .3, dfi = .01, scale = .8, m20,m21,m22;
    double vert[][][], vert1[][][], Norm[][][][], Norm1z[][][], M[];
    Image buffImage;     Graphics buffGraphics;
    Choice chRc, chL;    Label lbRc, lbL;    Button btNew;
    Color[][] col;
    boolean painted;
  
  public void init(){
    w = getSize().width - 30;
    h = getSize().height;   w2 = w/2;  h2 = h/2;
    String s=getParameter("N");  if (s != null) n = Integer.parseInt(s);
    s=getParameter("Rc");  if (s != null) Rc = Integer.parseInt(s);
    xPol = new int[3];  yPol = new int[3];
    buffImage = createImage(w, h);   buffGraphics = buffImage.getGraphics();
    col = new Color[2][256];
    for (int i = 0; i < 256; i++){
     col[0][i] = new Color(0, 0, i);
     col[1][i] = new Color(0, i, 0);}
    s = getParameter("bgColor"); if (s != null){
    StringTokenizer st = new StringTokenizer(s);
     int red = Integer.parseInt(st.nextToken());
     int green = Integer.parseInt(st.nextToken());
     int blue = Integer.parseInt(st.nextToken());
     setBackground( new Color(red, green, blue));}
    else setBackground(new Color(255,255,255));
    lbL = new Label("L", Label.RIGHT);  add(lbL);
    chL = new Choice();
    for (int i = 0, r = 32; i < 4; i++){
      chL.addItem(Integer.toString(r));  r *= 2;}
    chL.select("" + n);  chL.addItemListener(this);  add(chL);
    lbRc = new Label("Rc", Label.RIGHT);  add(lbRc);
    chRc = new Choice();
    for (int i = 0, r = 1; i < 5; i++){
      chRc.addItem(Integer.toString(r));  r *= 2;}
    chRc.select("" + Rc);  chRc.addItemListener(this);  add(chRc);
    btNew = new Button("New");   btNew.addActionListener(this);
    add(btNew);
    addMouseListener(this);  addMouseMotionListener(this);
    landscape();
    make3D();
  }
  
  public void make3D(){
    vert = new double[n1][n1][3];  vert1 = new double[n1][n1][2];
    double dx = w/(double)n;
    for (int i = 0; i < n1; i++) 
     for (int j = 0; j < n1; j++){
      vert[i][j][0] = dx*i - w2;  vert[i][j][2] = dx*j - w2;
      double m = M[i+n1*j];
      if (m < Vp) m = Vp;
      vert[i][j][1] = w*m - w2/2;}
    Norm = new double[n1][n1][2][3];  Norm1z = new double[n1][n1][2];
    iCol = new int[n][n][2];
    for (int i = 0; i < n; i++)
     for (int j = 0; j < n; j++){
      double s =
        ((vert[i][j][1] + vert[i+1][j][1] + vert[i+1][j+1][1])/3 + w2/2)/w;
      if (s < Vp+.0001) iCol[i][j][0] = 0;
      else  iCol[i][j][0] = 1;
      s = ((vert[i][j][1] + vert[i][j+1][1] + vert[i+1][j+1][1])/3 + w2/2)/w;
      if (s < Vp+.0001) iCol[i][j][1] = 0;
      else  iCol[i][j][1] = 1;
      Norm[i][j][0][0] = vert[i][j][1] - vert[i+1][j][1];
      Norm[i][j][0][1] = dx;
      Norm[i][j][0][2] = vert[i+1][j][1] - vert[i+1][j+1][1];
      double mod = Math.sqrt(Norm[i][j][0][0]*Norm[i][j][0][0] + Norm[i][j][0][1]*
       Norm[i][j][0][1] + Norm[i][j][0][2]*Norm[i][j][0][2]) / 255.5;
      Norm[i][j][0][0] /= mod; Norm[i][j][0][1] /= mod; Norm[i][j][0][2] /= mod;
      Norm[i][j][1][0] = vert[i][j+1][1] - vert[i+1][j+1][1];
      Norm[i][j][1][1] = dx;
      Norm[i][j][1][2] = vert[i][j][1] - vert[i][j+1][1];
      mod = Math.sqrt(Norm[i][j][1][0]*Norm[i][j][1][0] + Norm[i][j][1][1]*
       Norm[i][j][1][1] + Norm[i][j][1][2]*Norm[i][j][1][2]) / 255.5;
      Norm[i][j][1][0] /= mod; Norm[i][j][1][1] /= mod; Norm[i][j][1][2] /= mod;}
    rotate();
  }
  
  public void landscape(){
    n1 = n+1;
    int nc=n, Max=n1*n1, ncn1;
    M = new double[Max];
    double f[][] = new double[n1+64][n1+64];
    for (int i = 0; i < n1+64; i++)
     for (int j = 0; j < n1+64; j++) f[i][j] = 2*Math.random() - 1;
  //  f[100][100] = 1;
    int Lc = 2*Rc;
    double Rc2 = Rc*Rc;
    double G[][] = new double[32][32];
    G[0][0] = 1;
    for (int i = 1; i < Lc; i++){
     G[0][i] = Math.exp(-(i*i/Rc2));
     for (int j = 1; j <= i; j++) G[j][i] = G[0][i]*G[0][j];}
    Vs = 0;
    Vmin = 100; Vmax = -100;
    int t = 0, n33 = n1+32;
    for (int i = 32; i < n33; i++){
     for (int j = 32; j < n33; j++){
      double s = G[0][0]*f[i][j];
      for (int m = 1; m < Lc; m++){
       int im = i+m, i_m = i-m, jm = j+m, j_m = j-m;
       s += G[0][m]*(f[im][j]+f[i_m][j]+f[i][jm]+f[i][j_m]) +
            G[m][m]*(f[im][jm]+f[i_m][jm]+f[im][j_m]+f[i_m][j_m]);
       for (int n = 1; n < m; n++){
        int in = i+n, i_n = i-n, jn = j+n, j_n = j-n;
        s += G[n][m]*(f[im][jn]+f[i_m][jn]+f[im][j_n]+f[i_m][j_n] +
                      f[in][jm]+f[i_n][jm]+f[in][j_m]+f[i_n][j_m]);}}
      s *= 0.02;
      M[t++] = s;
      Vs += s;
      if (s > Vmax) Vmax = s;
      if (s < Vmin) Vmin = s;}}
      Vs /= Max;
  }
  
  public void destroy() {
    removeMouseListener(this);  removeMouseMotionListener(this);
  }
  public void actionPerformed(ActionEvent e){
    landscape();
    make3D();
    repaint();
  }
  public void itemStateChanged(ItemEvent e){
    Object src = e.getSource();
    if (src == chRc)
     Rc = Integer.parseInt(chRc.getSelectedItem());
    if (src == chL)
     n = Integer.parseInt(chL.getSelectedItem());
    landscape();
    make3D();
    repaint();
  }
  public void mouseClicked(MouseEvent e){}       // event handling
  public void mousePressed(MouseEvent e) {
    mx0 = e.getX();  my0 = e.getY();
    e.consume();
  }
  public void mouseReleased(MouseEvent e){}
  public void mouseEntered(MouseEvent e) {}
  public void mouseExited(MouseEvent e)  {}
  public void mouseMoved(MouseEvent e) {}
  public void mouseDragged(MouseEvent e) {
    int x1 = e.getX();  int y1 = e.getY();
    if( e.getX() < w){
      if ( e.isShiftDown() )  scale *= Math.exp(-(y1 - my0)/(double)w);
      else   fiX += dfi*(y1 - my0);
      fiY += dfi*(x1 - mx0);   mx0 = x1;  my0 = y1;
      rotate();}
    else{
      Vp = Vmax - y1*(Vmax-Vmin)/h;
    make3D();}
    repaint();
    e.consume();
  }
  public void rotate(){
    double ct = Math.cos(fiX), cf = Math.cos(fiY),
           st = Math.sin(fiX), sf = Math.sin(fiY),
           m00 =  scale*cf,    m02 =  scale*sf,
           m10 = scale*st*sf, m11 =  scale*ct, m12 = -scale*st*cf;
           m20 = -ct*sf; m21 = st; m22 = ct*cf;
    for (int i = 0; i < n1; i++)
     for (int j = 0; j < n1; j++){
      vert1[i][j][0] = m00*vert[i][j][0] + m02*vert[i][j][2];
      vert1[i][j][1] = m10*vert[i][j][0] + m11*vert[i][j][1] + m12*vert[i][j][2];}
    for (int i = 0; i < n; i++)
     for (int j = 0; j < n; j++)
      for (int k = 0; k < 2; k++)
       Norm1z[i][j][k] = m20*Norm[i][j][k][0] + m21*Norm[i][j][k][1] +
        m22*Norm[i][j][k][2];
    painted = false;
  }
  public void paint(Graphics g) {
   if ( !painted ){
    buffGraphics.clearRect(0, 0, w, h);
    int ib=0, ie=n, sti=1,  jb=0, je=n, stj=1;
    if (m20 < 0){ ib = n; ie = -1; sti = -1;}
    if (m22 < 0){ jb = n; je = -1; stj = -1;}
    for (int i = ib; i != ie; i += sti)
     for (int j = jb; j != je; j += stj){
      if (Norm1z[i][j][0] > 0){
       xPol[0] = w2 + (int)vert1[i][j][0];
       xPol[1] = w2 + (int)vert1[i+1][j][0];
       xPol[2] = w2 + (int)vert1[i+1][j+1][0];
       yPol[0] = h2 - (int)vert1[i][j][1];
       yPol[1] = h2 - (int)vert1[i+1][j][1];
       yPol[2] = h2 - (int)vert1[i+1][j+1][1];
       buffGraphics.setColor(col[iCol[i][j][0]][(int)(Norm1z[i][j][0])]);
       buffGraphics.fillPolygon(xPol,yPol, 3);}
      if (Norm1z[i][j][1] > 0){
       xPol[0] = w2 + (int)vert1[i][j][0];
       xPol[1] = w2 + (int)vert1[i][j+1][0];
       xPol[2] = w2 + (int)vert1[i+1][j+1][0];
       yPol[0] = h2 - (int)vert1[i][j][1];
       yPol[1] = h2 - (int)vert1[i][j+1][1];
       yPol[2] = h2 - (int)vert1[i+1][j+1][1];
       buffGraphics.setColor(col[iCol[i][j][1]][(int)(Norm1z[i][j][1])]);
       buffGraphics.fillPolygon(xPol,yPol, 3);} }
    painted = true;}
   g.drawImage(buffImage, 0, 0, this);
   g.setColor(Color.blue);
   g.fillRect(w+10,0, 20,h);
   g.setColor(Color.white);
   int y = h - (int)(h*(Vs-Vmin)/(Vmax-Vmin));
   g.drawLine(w+10,y, w+30,y);
   g.setColor(Color.yellow);
   y = h - (int)(h*(Vp-Vmin)/(Vmax-Vmin));
   g.drawLine(w+10,y, w+30,y);
  // showStatus( "n=" + n);
  }
  public void update(Graphics g){ paint(g); }
  
  }