C..1.1 Perspective Projection

The call glFrustuml, r, b, t, n, f(l, r, b, t, n, f) generates $R$, where:

$$R = \pmatrix{{{2n} \over {r-l}}& 0 & {{r+l} \over {r-l}} & 0\... ...& -1\cr 0 & 0 & {-{f-n} \over {2fn}} & {{f+n} \over {2fn}}\cr}$$

$R$ is defined as long as $l \neq r$, $t \neq b$, and $n \neq f$.