CIRCLES
The circle is the essential basis for drawing
cylindrical objects, arches, and other circular forms.
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- - - The perspective view of a circle remains acircle
when it is parallel to the picture plane (PP).
--------. The perspective view of a circle is a straight line
--+----.L-~---+----++---+--__.'--++-when the sightlines radiating from the station
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point (SP) are para !lei to the plane of the circle.
This occurs most frequently when the plane of the
circle is horizontal and at the height of the horizon
line (HL ), or when the plane of the circle is vertical
and aligned with the central axis of vision (CAV).
• In all other cases, circles appear as elliptical
shapes in perspective.
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• To draw acircle in perspective, we first draw a
perspective view of a square that circumscribes
the circle.
• Then we construct the diagonals of the square and
indicate where the circle crosses the diagonals
with additional lines parallel to the sides of the
square or tangent to the circumference of the
circle. The larger the circle, the more subdivisions
are necessary to ensure smoothness of the
elliptical shape.
• Note that the major axis of the ellipse
representing the circle in perspective is not
coincident with the geometric diameter of the
circle.
• We tend to see things as we b
elieve them to be.
So while acirclein perspective appears to be an
ellipse, we tend to see it in the m eye as a
ind's
circle, and thus exaggerate the length of its minor
axis.
• The minor axis should appear to be perpendicular
to the plane of the circle. Checking the relationship
between the major and minor axes of elliptical
shapes helps to ensure accuracy of the
foreshortening of circles in perspective.
PERSPECTIVE DRAWINGS/ 121