title: GLM - Calculating the frustum from the projection matrix
body: <p>GLM provides a way to declare a projection matrix:</p>
  
  <p>projectionMatrix = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 1000.f);</p>
  
  <p>From this, I want to be able to check to see if bounding boxes are in my frustum. How do I obtain the frustum planes or whatever it is I would need to calculate this from the projection matrix? Is this even the correct way to do it?</p>