Perspective Transformation

\[\M{P}=\begin{bmatrix} \frac{1}{r \tan\alpha/2} & 0 & 0 & 0 \\ 0 & \frac{1}{\tan\alpha/2} & 0 & 0 \\ \phantom{\frac{}{}}0 & 0 & \frac{n+f}{n-f} & \frac{2\,n\,f}{n-f} \\ \phantom{\frac{}{}}0 & 0 & -1 & 0 \\ \end{bmatrix}\]