This method, which is easy when you know it, has certain drawbacks, the chief one being that if we require a long-distance point, and a small angle, such as 10° on one side, and 80° on the other, then the size of the diagram becomes so large that it has to be carried out on the floor of the studio with long strings, &c., which is a very clumsy and unscientific way of setting to work. The architects in such cases make use of the centrolinead, a clever mechanical contrivance for getting over the difficulty of the far-off vanishing point, but by the method I have shown you, and shall further illustrate, you will find that you can dispense with all this trouble, and do all your perspective either inside the picture or on a very small margin outside it.
Perhaps another drawback to this method is that it is not self-evident, as in the former one, and being rather difficult to explain, the student is apt to take it on trust, and not to trouble about the reasons for its construction: but to show that it is equally correct, I will draw the two methods in one figure.
TWO METHODS OF ANGULAR PERSPECTIVE IN ONE FIGURE
It matters little whether the station-point is placed above or below the horizon, as the result is the same. In Fig. 125 it is placed above, as the lower part of the figure is occupied with the geometrical plan of the other method.
In each case we make the square _K_ the same size and at the same angle, its near corner being at _A_. It must be seen that by whichever method we work out this perspective, the result is the same, so that both are correct: the great advantage of the first or geometrical system being, that we can place the square at any angle, as it is drawn without reference to vanishing points.
We will, however, work out a few figures by the second method.
As in a previous figure (124) we found the various working points of angular perspective, we need now merely transfer them to the horizontal line in this figure, as in this case they will answer our purpose perfectly well.
Let _A_ be the nearest angle touching the base. Draw AV1, AV2. From _A_, raise vertical _Ae_, the height of the cube. From _e_ draw eV1, eV2, from the other angles raise verticals _bf_, _dh_, _cg_, to meet eV1, eV2, fV2, &c., and the cube is complete.