topical media & game development
[] 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) _

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#javascript-processing-example-topic-interaction-follow2.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>Follow2</h2>
  
  <p>Based on code from Keith Peters (www.bit-101.com). 
  
  A two-segmented arm follows the cursor position. The relative
  angle between the segments is calculated with atan2() and the
  position calculated with sin() and cos().</p>
  
  <p><a href="http://processing.org/learning/topics/follow2.html"><b>Original Processing.org Example:</b> Follow2</a><br>
  <script type="application/processing">
  float[] x = new float[2];
  float[] y = new float[2];
  float segLength = 50;
  
  void setup() {
    size(200, 200);
    smooth(); 
    strokeWeight(20.0);
    stroke(0, 100);
  }
  
  void draw() {
    background(226);
    dragSegment(0, mouseX, mouseY);
    dragSegment(1, x[0], y[0]);
  }
  
  void dragSegment(int i, float xin, float yin) {
    float dx = xin - x[i];
    float dy = yin - y[i];
    float angle = atan2(dy, dx);  
    x[i] = xin - cos(angle) * segLength;
    y[i] = yin - sin(angle) * segLength;
    segment(x[i], y[i], angle);
  }
  
  void segment(float x, float y, float a) {
    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>
  float[] x = new float[2];
  float[] y = new float[2];
  float segLength = 50;
  
  void setup() {
    size(200, 200);
    smooth(); 
    strokeWeight(20.0);
    stroke(0, 100);
  }
  
  void draw() {
    background(226);
    dragSegment(0, mouseX, mouseY);
    dragSegment(1, x[0], y[0]);
  }
  
  void dragSegment(int i, float xin, float yin) {
    float dx = xin - x[i];
    float dy = yin - y[i];
    float angle = atan2(dy, dx);  
    x[i] = xin - cos(angle) * segLength;
    y[i] = yin - sin(angle) * segLength;
    segment(x[i], y[i], angle);
  }
  
  void segment(float x, float y, float a) {
    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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