DOI Page / Citation link:
https://doi.org/10.11588/diglit.25683#0040
26
PRACTICAL PERSPECTIVE,
PLATE III..
Sect. 9- AS in the two foregoing plates the Illrd and IVth observ. of sect. 2, were*
exemplified, so in this will be found examples of the Vth, in which it is said chat all sloping
walls, roofs of houses, hills, &c. must tend to some point either above or below the hori-
zontal line.
I. Having determined the horizontal line, the point of sight, and the distance, con*
sider what angles any leading object makes-with the Picture; as, for instance, the pedestal
in front, parallel to the left side of which rises the first flight of steps.
If. At the point E, construct those angles-* (as directed by observ. III. § 7-) and?
observe where their sides, cut the horizontal line as in Yb and Yc, and Jay the distances
of the vanishing points so found from Vc to Dc, and from Yb to Db, and construct the
pedestal as in the example given in the last section.
III. At Yb, which is the vanishing point for all lines parallel to the left side of the
pedestal, draw a line perpendicular to the horizontal line.
IV. If the angle which the first rise of the steps makes with level ground be known,,
make at 13b (which is the distance of Vb), that angle with the horizontal line, and mark,
where its side rising cuts the perpendicular raised at the vanishing point, as in Yd.
V. When the slope rises from the spectator, the angle is constructed above the
horizontal line: when the slope descends from the spectator, tiie angle must be beneath the
horizontal line.
* Those angles are not given here, and in taking views they cannot be supposed to be as accurately determined
as when a piece of architecture is the subject to oe drawn: but it must be remembered, that whatevei angle is
assumed as the apparent angle, which the side of a building, &c. is supposed to make with the plane of the pictuie,
the other angles of the building must be made to conform therewith: as if, for instance, the sides aie at right
angles to each other, the correspondent angle at E must be the complement oi the assumed angle.
PRACTICAL PERSPECTIVE,
PLATE III..
Sect. 9- AS in the two foregoing plates the Illrd and IVth observ. of sect. 2, were*
exemplified, so in this will be found examples of the Vth, in which it is said chat all sloping
walls, roofs of houses, hills, &c. must tend to some point either above or below the hori-
zontal line.
I. Having determined the horizontal line, the point of sight, and the distance, con*
sider what angles any leading object makes-with the Picture; as, for instance, the pedestal
in front, parallel to the left side of which rises the first flight of steps.
If. At the point E, construct those angles-* (as directed by observ. III. § 7-) and?
observe where their sides, cut the horizontal line as in Yb and Yc, and Jay the distances
of the vanishing points so found from Vc to Dc, and from Yb to Db, and construct the
pedestal as in the example given in the last section.
III. At Yb, which is the vanishing point for all lines parallel to the left side of the
pedestal, draw a line perpendicular to the horizontal line.
IV. If the angle which the first rise of the steps makes with level ground be known,,
make at 13b (which is the distance of Vb), that angle with the horizontal line, and mark,
where its side rising cuts the perpendicular raised at the vanishing point, as in Yd.
V. When the slope rises from the spectator, the angle is constructed above the
horizontal line: when the slope descends from the spectator, tiie angle must be beneath the
horizontal line.
* Those angles are not given here, and in taking views they cannot be supposed to be as accurately determined
as when a piece of architecture is the subject to oe drawn: but it must be remembered, that whatevei angle is
assumed as the apparent angle, which the side of a building, &c. is supposed to make with the plane of the pictuie,
the other angles of the building must be made to conform therewith: as if, for instance, the sides aie at right
angles to each other, the correspondent angle at E must be the complement oi the assumed angle.