[ LVI]
How to put a Given Square into Angular Perspective
Let ABCD (Fig. 115) be the given square on the geometrical plane, where we can place it as near or as far from the base and at any angle that we wish. We then proceed to find its perspective on the picture by finding the perspective of the four points ABCD as already shown. Note that the two sides of the perspective square dc and ab being produced, meet at point V on the horizon, which is their vanishing point, but to find the point on the horizon where sides bc and ad meet, we should have to go a long way to the left of the figure, which by this method is not necessary.
Fig. 115.