topical media & game development
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#javascript-processing-example-topic-interaction-reach3.htm / htm



  <!DOCTYPE html>
  <html><head>
  <script src="javascript-processing-example-processing.js"></script>
  <script src="javascript-processing-example-init.js"></script>
  <link rel="stylesheet" href="javascript-processing-example-style.css">
  </head><body><h1><a href="http://ejohn.org/blog/processingjs/">Processing.js</a></h1>
  <h2>Reach3</h2>
  
  <p>Based on code from Keith Peters (www.bit-101.com)
  
  The arm follows the position of the ball by
  calculating the angles with atan2().</p>
  
  <p><a href="http://processing.org/learning/topics/reach3.html"><b>Original Processing.org Example:</b> Reach3</a><br>
  <script type="application/processing">
  int numSegments = 6;
  float[] x = new float[numSegments];
  float[] y = new float[numSegments];
  float[] angle = new float[numSegments];
  float segLength = 15;
  float targetX, targetY;
  
  float ballX = 50;
  float ballY = 50;
  int ballXDirection = 1;
  int ballYDirection = -1;
  
  void setup() {
    size(200, 200);
    smooth(); 
    strokeWeight(20.0);
    stroke(0, 100);
    noFill();
    x[x.length-1] = width/2;     // Set base x-coordinate
    y[x.length-1] = height;  // Set base y-coordinate
  }
  
  void draw() {
    background(226);
    
    strokeWeight(20);
    ballX = ballX + 1.0 * ballXDirection;
    ballY = ballY + 0.8 * ballYDirection;
    if(ballX > width-25 || ballX < 25) {
      ballXDirection *= -1; 
    }
    if(ballY > height-25 || ballY < 25) {
      ballYDirection *= -1; 
    }
    ellipse(ballX, ballY, 30, 30);
    
    reachSegment(0, ballX, ballY);
    for(int i=1; i<numSegments; i++) {
      reachSegment(i, targetX, targetY);
    }
    for(int i=x.length-1; i>=1; i--) {
      positionSegment(i, i-1);  
    } 
    for(int i=0; i<x.length; i++) {
      segment(x[i], y[i], angle[i], (i+1)*2); 
    }
  }
  
  void positionSegment(int a, int b) {
    x[b] = x[a] + cos(angle[a]) * segLength;
    y[b] = y[a] + sin(angle[a]) * segLength; 
  }
  
  void reachSegment(int i, float xin, float yin) {
    float dx = xin - x[i];
    float dy = yin - y[i];
    angle[i] = atan2(dy, dx);  
    targetX = xin - cos(angle[i]) * segLength;
    targetY = yin - sin(angle[i]) * segLength;
  }
  
  void segment(float x, float y, float a, float sw) {
    strokeWeight(sw);
    pushMatrix();
    translate(x, y);
    rotate(a);
    line(0, 0, segLength, 0);
    popMatrix();
  }
  </script><canvas width="200" height="200"></canvas></p>
  <div style="overflow: hidden; height: 0px; width: 0px;"></div>
  
  <pre><b>// All Examples Written by <a href="http://reas.com/">Casey Reas</a> and <a href="http://benfry.com/">Ben Fry</a>
  // unless otherwise stated.</b>
  int numSegments = 6;
  float[] x = new float[numSegments];
  float[] y = new float[numSegments];
  float[] angle = new float[numSegments];
  float segLength = 15;
  float targetX, targetY;
  
  float ballX = 50;
  float ballY = 50;
  int ballXDirection = 1;
  int ballYDirection = -1;
  
  void setup() {
    size(200, 200);
    smooth(); 
    strokeWeight(20.0);
    stroke(0, 100);
    noFill();
    x[x.length-1] = width/2;     // Set base x-coordinate
    y[x.length-1] = height;  // Set base y-coordinate
  }
  
  void draw() {
    background(226);
    
    strokeWeight(20);
    ballX = ballX + 1.0 * ballXDirection;
    ballY = ballY + 0.8 * ballYDirection;
    if(ballX &gt; width-25 || ballX &lt; 25) {
      ballXDirection *= -1; 
    }
    if(ballY &gt; height-25 || ballY &lt; 25) {
      ballYDirection *= -1; 
    }
    ellipse(ballX, ballY, 30, 30);
    
    reachSegment(0, ballX, ballY);
    for(int i=1; i&lt;numSegments; i++) {
      reachSegment(i, targetX, targetY);
    }
    for(int i=x.length-1; i&gt;=1; i--) {
      positionSegment(i, i-1);  
    } 
    for(int i=0; i&lt;x.length; i++) {
      segment(x[i], y[i], angle[i], (i+1)*2); 
    }
  }
  
  void positionSegment(int a, int b) {
    x[b] = x[a] + cos(angle[a]) * segLength;
    y[b] = y[a] + sin(angle[a]) * segLength; 
  }
  
  void reachSegment(int i, float xin, float yin) {
    float dx = xin - x[i];
    float dy = yin - y[i];
    angle[i] = atan2(dy, dx);  
    targetX = xin - cos(angle[i]) * segLength;
    targetY = yin - sin(angle[i]) * segLength;
  }
  
  void segment(float x, float y, float a, float sw) {
    strokeWeight(sw);
    pushMatrix();
    translate(x, y);
    rotate(a);
    line(0, 0, segLength, 0);
    popMatrix();
  }</pre>
  </body></html>
[] readme course(s) preface I 1 2 II 3 4 III 5 6 7 IV 8 9 10 V 11 12 afterthought(s) appendix reference(s) example(s) resource(s) _

(C) Æliens 20/2/2008

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