import java.awt.*;
import java.awt.image.*;

public class SineWaves extends java.applet.Applet implements Runnable {
  Image img;
  Thread runThread;
  long firstFrame, frames, fps;
  int width, height;
  int w=64, h=64;
  int[] waveTable=new int[256];
  int[] xPoints=new int[w+3];
  int[] yPoints=new int[w+3];
  boolean ready;

  public void init() {
     width = size().width;
     height = size().height;
     img=createImage(width, height);
  }

  public void start() {
     if (runThread == null) {
       runThread=new Thread(this);
       runThread.start();
       firstFrame=System.currentTimeMillis();
       frames = 0;
       ready = false;
     };
  }

  public void stop() {
    if (runThread != null) {
       runThread.stop();
       runThread=null;
    }
  }

  public void update(Graphics g) {
     if (ready) {
        g.drawImage(img, 0, 0, null);
        frames++;
        fps = (frames*10000) / (System.currentTimeMillis()-firstFrame);
        g.drawString(fps/10 + "." + fps%10 + " fps", 2, height - 2);
     }
  }

  void calculateWaveTable() {
    for(int i=0;i<256;i++)
      waveTable[i]=(int)(32*(1+Math.sin(((double)i*2*Math.PI)/256)));
  }

  public void run() {
    int x,y;
    int index;
    int tempval,result;
    int spd1=2,spd2=5,spd3=1,spd4=4;
    int pos1=0,pos2=0,pos3=0,pos4=0;
    int tpos1,tpos2,tpos3,tpos4;
    int inc1=6,inc2=3,inc3=3,inc4=9;
    Graphics ig = img.getGraphics();

    runThread.setPriority(Thread.MIN_PRIORITY);
    calculateWaveTable();
    while(true) {
      ig.setColor(Color.white);
      ready=false;
      ig.fillRect(0,0,width,height);
      ig.setColor(Color.black);
      tpos1=pos1; tpos2=pos2; tpos3=pos3; tpos4=pos4;
      for(int i=0;i<h;i++) {
         tpos1&=255;
         yPoints[i]=i*4;
         xPoints[i]=waveTable[tpos1]*2;
         tpos1+=inc1;
      }
      xPoints[w]=xPoints[w-1];
      yPoints[w]=w*4;
      xPoints[w+1]=0;
      yPoints[w+1]=w*4;
      xPoints[w+2]=0;
      yPoints[w+2]=0;
      ig.drawPolygon(xPoints, yPoints, w+3);
      for(int i=0;i<h;i++) {
         tpos2&=255;
         yPoints[i]=i*4;
         xPoints[i]=waveTable[tpos2]*2;
         tpos2+=inc2;
      }
      xPoints[w]=xPoints[w-1];
      yPoints[w]=w*4;
      xPoints[w+1]=0;
      yPoints[w+1]=w*4;
      xPoints[w+2]=0;
      yPoints[w+2]=0;
      ig.drawPolygon(xPoints, yPoints, w+3);
      for(int i=0;i<h;i++) {
         tpos3&=255;
         yPoints[i]=height-waveTable[tpos3]*2;
         xPoints[i]=i*4;
         tpos3+=inc3;
      }
      xPoints[w]=xPoints[w-1]+4;
      yPoints[w]=yPoints[w-1];
      xPoints[w+1]=w*4;
      yPoints[w+1]=w*4;
      xPoints[w+2]=0;
      yPoints[w+2]=w*4;
      ig.drawPolygon(xPoints, yPoints, w+3);
      for(int i=0;i<h;i++) {
         tpos4&=255;
         yPoints[i]=height-waveTable[tpos4]*2;
         xPoints[i]=i*4;
         tpos4+=inc4;
      }
      xPoints[w]=xPoints[w-1]+4;
      yPoints[w]=yPoints[w-1];
      xPoints[w+1]=w*4;
      yPoints[w+1]=w*4;
      xPoints[w+2]=0;
      yPoints[w+2]=w*4;
      ig.drawPolygon(xPoints, yPoints, w+3);
      pos1+=spd1; pos2+=spd2; pos3+=spd3; pos4+=spd4;
      ig.drawRect(0,0,width-1,height-1);
      ready=true;
      repaint();
      try {Thread.sleep(20);}
      catch (InterruptedException e) { }
    }
  }

}