in tutorial 4, at the end, "Further Study" section, it is asked to try with a variable eye point and arbitrary perspective plane location..
I can't figure it out how I should do if I would like to have, lets say, the eye point on (0, 0, 3) looking in the X+, so i.e. toward (1, 0, 3). Basically you are looking at the rendering from the left side now.
Ps: sorry if I ask here but I did not know where else I could have asked that..