title: Trouble converting matrix to quaternion and back
body: <p>I am trying to store my rotation matrix as a quaternion and then when I want to use it for transformation, convert it back. I am using the glm library which provides mat4_cast and quat_cast for these. However, when I execute the following code:</p>
  
  <pre><code>glm::mat4 origTest = glm::lookAt(position, lookAtPt, up);
  glm::quat quatTest = glm::quat_cast(origTest);
  glm::mat4 mat4Test = glm::mat4_cast(quatTest);
  </code></pre>
  
  <p>I get different values for origTest and mat4Test. Am I missing something here? 
  position, lookAtPt and up are glm::vec3.</p>