title: Random number in OpenGL GLSL fragment shader
body: <p>I have been looking at a lot of questions regarding generating a random number in the fragment shader. However, none of them are of shape:</p>
  
  <pre><code>float rand() {
      ...
      return random_number;
  }
  </code></pre>
  
  <p>All of them require a input parameter. Is there any way to get a random number without any input?</p>