The Theory and Practice of Perspective

by G. A. Storey

Fig. 123.

[ LXII]

Another Method of Angular Perspective, being that Adopted in our Art Schools

In the previous method we have drawn our squares by means of a geometrical plan, putting each point into perspective as required, and then by means of the perspective drawing thus obtained, finding our vanishing and measuring points. In this method we proceed in exactly the opposite way, setting out our points first, and drawing the square (or other figure) afterwards.

Fig. 124.

Having drawn the horizontal and base lines, and fixed upon the position of the point of sight, we next mark the position of the spectator by dropping a perpendicular, S ST, from that point of sight, making it the same length as the distance we suppose the spectator to be from the picture, and thus we make ST the station-point.

To understand this figure we must first look upon it as a ground-plan or bird’s-eye view, the line V²V¹ or horizon line representing the picture seen edgeways, because of course the station-point cannot be in the picture itself, but a certain distance in front of it. The angle at ST, that is the angle which decides the positions of the two vanishing points V¹, V², is always a right angle, and the two remaining angles on that side of the line, called the directing line, are together equal to a right angle or 90°. So that in fixing upon the angle at which the square or other figure is to be placed, we say ‘let it be 60° and 30°, or 70° and 20°’, &c. Having decided upon the station-point and the angle at which the square is to be placed, draw TV¹ and TV², till they cut the horizon at V¹ and V². These are the two vanishing points to which the sides of the figure are respectively drawn. But we still want the measuring points for these two vanishing lines. We therefore take first, V¹ as centre and V¹T as radius, and describe arc of circle till it cuts the horizon in M¹, which is the measuring point for all lines drawn to V¹. Then with radius V²T describe arc from centre V² till it cuts the horizon in M², which is the measuring point for all vanishing lines drawn to V². We have now set out our points. Let us proceed to draw the square Abcd. From A, the nearest angle (in this instance touching the base line), measure on each side of it the equal lengths AB and AE, which represent the width or side of the square. Draw EM² and BM¹ from the two measuring points, which give us, by their intersections with the vanishing lines AV¹ and AV², the perspective lengths of the sides of the square Abcd. Join b and V¹ and dV², which intersect each other at C, then Adcb is the square required.