What I don't like about TFA is the inconsistent, sloppy use of coordinates. Initially x,y,z are relative to the viewer with z going from the eye to the object.

What I don't like about TFA is the inconsistent, sloppy use of coordinates. Initially x,y,z are relative to the viewer with z going from the eye to the object. Some paragraphs later x,y are the horizontal plane with z going up. Then x and y are swapped (to overlap x onto y you have to rotate it 90° clockwise, the opposite of trigonometry's standard), only to be swapped again in the picture that shows the value of the angles. Coming to screen coordinates, all formulas and text assumes that y grows down, which is customary, but not the pictures accompanying the explanation how to calculate screen position from y. Frankly, I'd expect more consistency from someone who invites his students to focus on the mathematical aspects, not only on the code.