title: Change Position Three.js / webgl vertex shader
body: <p>Hi I made a particle system, with three.js it uses normal JavaScript loops to change particle positions, but this is slow. </p>
  
  <p>Because of this I have started to learn how to transfer this to the GPU via shader.</p>
  
  <p>I have a problem, I cannot get the positions to change, each point stays at the same position.</p>
  
  <pre><code>var vertexShader = [
          'void main() {',
          '    vec3 newPosition = position.xyz;',
          '    newPosition.y += 10.0;',
          '    gl_PointSize = 1.00;',
          '    gl_Position = projectionMatrix * modelViewMatrix * vec4( newPosition, 1.0 );',
          '}',
      ].join('\n');
  </code></pre>
  
  <p>why does</p>
  
  <pre><code>'    newPosition.y += 10.0;',
  </code></pre>
  
  <p>not change the particle positions?</p>
  
  <p>Do I need some kind of time variable, I notice people seems to have these?
  Thanks.</p>