_The Manner of designing in Perspective without occult Lines._
Being desirous to make this Rule as easy as possible, I shall give a
farther Account of raising Solids without the Help of occult Lines, which
I only touch’d upon in the foregoing Figure. I therefore here shew you,
how the five shadow’d Cubes of this Figure are taken from their Plans and
Elevations.
Two things preparatory are to be done, and, if you please, on separate
Papers. The first is, to describe the Geometrical Plan and Elevation,
as you see in B and A. The second is, to dispose on the Ground-line the
Breadth of the Plan B; as, for Example, in NM, and the two next to it.
The Length thereof MX, drawn to the Point of Distance D, cuts the Visual
MO in R; and the Foreshortning E serves also for the other two Squares
plac’d upon the same Ground-line, whole Angles being directed to the
Distance D, give as many Angles on the Visuals NO, MO. This done, erect a
Perpendicular on the Angle N, which in Geometrical Elevations is always
necessary, and is the third Line mention’d in the first Figure. Then
carry the Height A on NF, drawing the Visuals FO, NO, which determine the
Height ST, and that of the other Squares.
It remains to be known, how to make use of the foresaid Preparation for
the Construction of the shadow’d Pedestals.
On another Paper therefore dispose the Horizontal and Ground-lines,
together with the Point of Sight O, and the Perpendicular V, keeping the
same Measures as in the aforesaid Preparation, and doing as I have done.
You may prove by the Compasses, that NF is equal to 1, 5, and 2, 6, and
measuring ST, you’ll find it equal to 7, 3, then drawing the level Lines,
and the Visuals to the Point of Sight, you have the upper Face of the
Cube C in 1, 2, 3, 4. The same must be done in the others. In a word, the
Angles of the Plan give you the perpendicular Lines, and the Angles of
the Elevation give the level Lines, or those parallel to the Ground-line;
and this you are always to understand for the future.