| Fig. 149 A. | Fig. 149 B. |
[ LXXX]
Perspective of a Square Placed at an Angle New Method
As we have drawn a triangle in a square so can we draw an oblique square in a parallel square. In Figure 150 A we have drawn the oblique square GEPn. We find the points on the base Am, as in the previous figures, which enable us to construct the oblique perspective square n·G·E·P· in the parallel perspective square Fig. 150 B. But it is not necessary to construct the geometrical figure, as I will show presently. It is here introduced to explain the method.
| Fig. 150 A. | Fig. 150 B. |
Fig. 150 B. To test the accuracy of the above, produce sides G·E· and n·P· of perspective square till they touch the horizon, where they will meet at V, their vanishing point, and again produce the other sides n·G· and P·E· till they meet on the horizon at the other vanishing point, which they must do if the figure is correctly drawn.
In any parallel square construct an oblique square from
a given point—given the parallel square at Fig. 150 B, and given point n· on base. Make A·f· equal to n·m·, draw f·S and n·S to point of sight. Where these lines cut the diagonal AC draw horizontals to P· and G·, and so find the four points G·E·P·n· through which to draw the square.