title: Question about 3D Picking in Android (with OpenGL ES 2)
body: <p>I need some help on 3D picking. </p>
  
  <p>I am using the way it works <a href="http://magicscrollsofcode.blogspot.com/2010/10/3d-picking-in-android.html" rel="nofollow">here</a>. In short, what I have is:</p>
  
  <pre><code>normalizedPoint[0] = (x * 2 / screenW) -1;
  normalizedPoint[1] = 1 - (y * 2 / screenH);
  normalizedPoint[2] = ?
  normalizedPoint[3] = ?
  </code></pre>
  
  <p>for 2 and 3, I have no idea what it should be (I put 1, -1 just like the reference, and it doesn't work)</p>
  
  <p>Then, for my root object (following just psuedo code):</p>
  
  <pre><code>matrix = perspective_matrix x model_matrix
  inv_matrix = inverse(matrix)
  outpoint = inv_matrix x normalizedPoint
  </code></pre>
  
  <p>That's what I have, but it doesn't work, the outPoint I receive is not even close to the point I am suppose clicking. I've been searching in web for more than a week. but no idea how to solve it. HELP!</p>