title: What does the glFrustum function do?
body: <p>According to MSDN, we are multiplying the current matrix with the perspective matrix. What matrix are we talking about here? Also from MSDN:</p>
  
  <blockquote>
    <p>"The glFrustum function multiplies the current matrix by this matrix, with the result replacing the current matrix. That is, if M is the current matrix and F is the frustum perspective matrix, then glFrustum replaces M with M • F."</p>
  </blockquote>
  
  <p>Now, from my current knowledge of grade 12 calculus (in which I am currently), M is a vector and M dot product F returns a scalar, so how can one replace a vector with a scalar?</p>
  
  <p>I'm also not sure what "clipping" planes are and how they can be referenced via one float value.</p>
  
  <p>Please phrase your answer in terms of the parameters, and also conceptually. I'd really appreciate that.</p>
  
  <p>I'm trying to learn openGL via this tutorial: <a href="http://www.youtube.com/watch?v=WdGF7Bw6SUg" rel="noreferrer">http://www.youtube.com/watch?v=WdGF7Bw6SUg</a>. It is actually not really good because it explains nothing or else it assumes one knows openGL. I'd really appreciate a link to a tutorial otherwise, I really appreciate your time and responses! I'm sure I can struggle through and figure things out.</p>