Selected Bibliography Architectural Graphics | Seite 124

INCLINED LINES
Once we are familiar with how lines parallel to the
three principal axes of an object converge in linear
perspective, we can use this rectilinear geometry as
the basisfor drawing perspective views of inclined
lines, circles, and irregular shapes.

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• Inclined lines parallel to the picture plane (PP)
retain their orientation but diminish in size
according to their distance from the spect ator. If
perpendicular or oblique to PP, however, an inclined
set of lines will appear to converge at a vanishing
point above or below the horizon line (HL).
• We can draw any inclined line in perspective by
first finding the perspective projections of its end
points and then connecting them. The easiest way
to do this is to visualize the inclined line as being
the hypotenuse of aright triangle. If we can draw
the sides of the triangle in proper perspective, we
can connect the end points to establish the
inclined line.

VPi

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• If we must draw a number of inclined parallel lines,
as in the case of a sloping roof, a ramp, or a
stairway, it is useful to know where the inclined
set appears to converge in perspective. An inclined
set of parallel lines is not horizontal and t herefore
will not converge on HL.Ifthe set rises upward as
it recedes, its vanishing point will be above HL;
if it falls as it recedes, it will appear to converge
below HL.
• An expedient method for determining the
vanishing point for an inclined set of lines (VPi)
is to extend one of the inclined lines until it
intersects a vertical line drawn through the
vanishing point (VP) for a horizontal line lying in
the same vertical plane. This intersection is the
vanishingpoint (VPi) for the inclined line and all
other lines parallel to it.