[ CVIII]
Method of Perspective Employed by Architects

The architects first draw a plan and elevation of the building to be put into perspective. Having placed the plan at the required angle to the picture plane, they fix upon the point of sight, and the distance from which the drawing is to be viewed. They then draw a line SP at right angles to the picture plane VV·, which represents that distance so that P is the station-point. The eye is generally considered to be the station-point, but when lines are drawn to that point from the ground-plan, the station-point

is placed on the ground, and is in fact the trace or projection exactly under the point at which the eye is placed. From this station-point P, draw lines PV and PV· parallel to the two sides of the plan ba and ad (which will be at right angles to each other), and produce them to the horizon, which they will touch at points V and V·. These points thus obtained will be the two vanishing points.

The next operation is to draw lines from the principal points of the plan to the station-point P, such as bP, cP, dP, &c., and where these lines intersect the picture plane (VV· here represents it as well as the horizon), drop perpendiculars b·B, aA, d·D, &c., to meet the vanishing lines AV, AV·, which will determine the points A, B, C, D, 1, 2, 3, &c., and also the perspective lengths of the sides of the figure AB, AD, and the divisions B, 1, 2, &c. Taking the height of the figure AE from the elevation, we measure it on Aa; as in this instance A touches the ground line, it may be used as a line of heights.

Fig. 197. A method of angular Perspective employed by architects.
[To face p. 171]

[Larger View]

I have here placed the perspective drawing under the ground plan to show the relation between the two, and how the perspective is worked out, but the general practice is to find the required measurements as here shown, to mark them on a straight edge of card or paper, and transfer them to the paper on which the drawing is to be made.