Page 98 - DCAP313_LAB_ON_COMPUTER_GRAPHICS

Lab on Computer Graphics

Notes 9. Engineering drawing commonly applies?
(a) oblique projection (b) orthographic projection

(c) perspective projection (d) None of above
10. ………….. informal high-level description of the operating principle of a computer program
or other algorithm.

(a) Pseudo Code (b) binary code
(c) ASSCII code (d) none of these

11. DDA stands for…
(a) Discrete Differential Analyzer (b) Digital Differential Analyzer
(c) Digital Data Analyzer (d) none of these
12. Midpoint ellipse algorithm is a method for drawing ellipses in computer graphics.

(a) True (b) False
13. Ellipses are useful in many applied scenarios, and in widely disparate fields.
(a) True (b) False

14. The advantage of midpoint modified method is that only addition operations are required
in the program loops.

(a) True (b) False
15. The Gauss-Green formula is used to determine the ellipse sector area between the two
points, and a triangular area is added or subtracted to give the segment area.
(a) True (b) False

5.5 Summary

• Ellipses are useful in many applied scenarios, and in widely disparate fields. In our research,
we have encountered a common need for efficiently calculating the overlap area between
two ellipses.

• Midpoint ellipse algorithm is a method for drawing ellipses in computer graphics. This
method is modified from Bresenham’s algorithm.

• The ellipse sector between two points (x 1 , y 1 ) and (x 2 , y 2 ) on the ellipse is the area that is
swept out by a vector from the origin to the ellipse, beginning at the first point (x 1 , y 1 ),
as the vector travels along the ellipse in a counter-clockwise direction from (x 1 , y 1 ) to
(x 2 , y 2 ).

• The ellipse is defined by specifying its semi-axes lengths, A > 0 and B > 0. The points are
passed to the algorithm as (x 1 , y 1 ) and (x 2 , y 2 ), both of which must be on the ellipse.
• If the polynomial solver returns either two or four real roots to the quadratic polynomial
of equation then the ellipse curves intersect.

5.6 Keywords

Algorithm: An algorithm is a step-by-step procedure for calculations. Algorithms are used for
calculation, data processing, and automated reasoning.

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