Lighting and Shading Applet -- Source


import java.awt.*;
import java.applet.*;
import java.lang.*;

class Source
{     public        int        top = 5;
      public        int        left;
      public        Color      button_back;
      public        Color      button_marker;
      public        int        marker_x = 0;
      public        int        marker_y = 0;
      public        double     vx = 0;
      public        double     vy = 0;
      public        double     vz = 1;

      public boolean in_button(int x, int y)
      {      return(((x - left - 50) * (x - left - 50) +
                     (y - top - 50) * (y - top - 50)) < 2500);
      }

      public void place_button(int x, int y)
      {      marker_x = x - left - 50;
             marker_y = y - top - 50;

             vx = marker_x/50.0;
             vy = -marker_y/50.0;
             vz = java.lang.Math.sqrt(1 - vx * vx - vy * vy);
      }
             

      public void draw_button(Graphics g)
      {      g.setColor(button_back);
             g.fillOval(left, top, 100, 100);
             g.setColor(button_marker);
             g.fillOval(marker_x + left + 47, marker_y + 50, 6, 6);
      }

      public Source(int left, Color button_back, Color button_marker)
      {      this.left = left;
             this.button_back = button_back;
             this.button_marker = button_marker;
      }
}

public class Monochrome extends Applet
{     
      Graphics    bG;
      Image       bI;

      public void init()
      {      
             bI = createImage(this.size().width, this.size().height);
             bG = bI.getGraphics();
      }

      public void update(Graphics g)
      {      
             paint(g);
      }

      Source white = 
             new Source(110, new Color(64, 64, 64), new Color(255, 255, 255));

      public boolean mouseDown(Event evt, int x, int y)
      {      if (white.in_button(x, y))
             { white.place_button(x, y);
               repaint(); 
             }
             return true;
      }

      public void paint(Graphics g)
      {      int     countx, county;
             double  x, y, z;
             double  workreal;
             int     work;
 
             white.draw_button(bG);

             for (countx = 2; countx <  103; countx = countx + 1)
                 {  for (county = 5; county < 106; county = county + 1)
                    {   x = (countx - 52.0) / 50.0;
                        y = -(county - 55.0) / 50.0;
                        if (x * x + y * y < 1.0)
                           { z = java.lang.Math.sqrt(1 - x * x - y * y);
                             workreal = x * white.vx + y * white.vy +
                                        z * white.vz;
                             workreal = java.lang.Math.max(0.0, workreal);
                             work = (int) java.lang.Math.round(workreal * 255);
                             bG.setColor(new Color(work, work, work));
                             bG.drawRect(countx, county, 1, 1);
                           }
                        if (x * x + y * y >= 1.0)
                           { bG.setColor(Color.black);
                             bG.drawRect(countx, county, 1, 1);
                           }
                    }
                    g.drawImage(bI, 0, 0, this);
                 }
 
      
      }
}