title: How to pass information from vertex shader to fragment shader if there is a geometry shader active?
body: <p>Before adding a geometry shader I declared a variable in the vertex shader:</p>
  
  <pre><code>out vec3 normal; 
  </code></pre>
  
  <p>To be received by the fragment shader as:</p>
  
  <pre><code>in vec3 normal; 
  </code></pre>
  
  <p>However if I add a geometry shader to the program, the linker tells me that normal has not been declared as an output from the prvious stage. But I am not sure how to recieve nor send the output in the geometry shader.</p>