title: Replacement for gluPerspective (with glFrustrum)
body: <p>How would you convert a gluPerspective function to glFrustum?  I have tried to use this equation, but have not had any luck as it did not generate the same image as it did with gluPerspective. </p>
  
  <blockquote>
    <p>top = tan(fov*3.14159/360.0) * near
    bottom = -top</p>
    
    <p>left = aspect * bottom
    right = aspect * top</p>
  </blockquote>
  
  <p>I can't seem to convert my field of view correctly. Say, for example, if my FOV was 45, what would be the 'top' param in the Frustum call?</p>