title: Can you modify a uniform from within the shader? If so. how?
body: <p>So I wanted to store all my meshes in one large VBO. The problem is, how do you do have just one draw call, but let every mesh have its own model to world matrix? </p>
  
  <p>My idea was to submit an array of matrices to a uniform before drawing. In the VBO I would make the color of every first vertex of a mesh negative (So I'd be using the signing bit to check whether a vertex was the first of a mesh).</p>
  
  <p>Okay, so I can detect when a new mesh has started and I have an array of matrices ready and probably a uniform called 'index'. But how do I increase this index by one every time I encounter a new mesh?</p>
  
  <p>Can you modify a uniform from within the shader? If so, how?</p>