title: How does glGetUniformBlockIndex know whether to look in the vertex shader or the fragment shader?
body: <p>I start by attaching to my program both shaders and then call <code>glGetUniformBlockIndex</code> to bind the uniform buffers. I would expect a <code>glBindShader</code> function to let me specify which shader I want to parse to find the uniform, but there is no such thing.
  How can I tell OpenGL which shader it should look into?</p>