[ XCII]
How to Draw a Circle in Angular Perspective
Let ABCD be the oblique square. Produce VA till it cuts the base line at G.
Fig. 174.
Take mD, the fourth of the base. Find mn as in Fig. 171, measure it on each side of E, and so obtain Ef and Ef·, and proceed to draw fV, EV, f·V and the diagonals, whose intersections with these lines will give us the eight points through which to draw the circle. In fact the process is the same as in parallel perspective, only instead of making our divisions on the actual base AD of the square, we make them on GD, the base line.
To obtain the central line hh passing through O, we can make use of diagonals of the half squares; that is, if the other vanishing point is inaccessible, as in this case.