title: in int gl_VertexID causing error with three.js
body: <p>I've been having trouble with the gl_VertexID built in vertex index, passed using <code>in</code>, to work with Three.js</p>
  
  <p>I'm not sure why, as the documentation says it works in all versions of OpenGL</p>
  
  <p><a href="http://www.opengl.org/sdk/docs/manglsl/xhtml/gl_VertexID.xml" rel="nofollow">http://www.opengl.org/sdk/docs/manglsl/xhtml/gl_VertexID.xml</a></p>
  
  <p>I'm using this vertex shader:</p>
  
  <pre><code>        uniform int freqData[64];
          uniform int fftSize;
  
          in int gl_VertexID;
  
          void main() {
              vec3 norm = normalize(position);
  
              int modFFT = mod(gl_VertexID, fftSize);
  
              vec3 newPosition = norm * float(freqData[modFFT]);
  
              gl_Position = projectionMatrix * modelViewMatrix * vec4( newPosition, 1.0 );
          }
  </code></pre>
  
  <p>The error I receive is:</p>
  
  <p><code>ERROR: 0:68: 'in' : syntax error</code></p>
  
  <p>It seems to have a problem with the <code>in</code> declaration, and it doesn't complain about anything else (the error console is able to detect multiple compilation errors).</p>
  
  <p>I very much appreciate your help, I'm working with yesterday's Three.js build.</p>