I am writing an OpenGL wrapper, and am trying to not use the helper libraries such as GLU. I am wondering what the math behind this function call is, so I can code a custom version of it to eliminate the use of GLU. Thanks in advance.
Do look out though, these pages have the positive Z-axis pointing out of the screen while the OpenGL Z-axis points into the screen. Also, the matrices used in the pages would have to be loaded into OpenGL like this: