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Conjugate diameter method-Cont. | Up
Illustrator Draftsman 3 & 2 - Volume 2 Standard Practices and Theory | Next
Parallelogram ellipses |
Ellipse construction, Continued
Conjugate
The conjugate diameter method of ellipse construction uses conjugate
diameter
diameters to project a circle and through a series of tangents, plot points on
method
the circumference of the ellipse.
To construct an ellipse using conjugate diameters, use this table;
Step
Action
1
Given two conjugate diameters (AB and DE) with C as a center,
use the distance from C to A as a radius to draw a circle with C as
the center.
2
Draw line (GF) perpendicular to AB and passing through C.
3
Draw lines connecting points D and F and points G and E.
4
Select any point (X) along AB and draw a line (PQ) parallel to DE
and RS parallel to FG.
5
Determine at least five points to each quadrant. For larger ellipses,
plot more points. The more points plotted the more accurate the
ellipse circumference.
6
Lightly sketch the outline of the ellipse. Darken the ellipse using
french curves.
Figure 2-50 illustrates the conjugate diameter method of ellipse construction.
Figure 2-50.—The
conjugate diameter
method.
Continued on next page
2-52
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