Page 58 - DCAP504_Computer Graphics

Unit 4: Scan Conversion I

The following figure 4.10 depicts arc generated using Bresenham’s Algorithm.

Figure 4.10: Arc Generated Using Bresenham’s Algorithm

Source: Computer Graphics, II edition, ZHIGANG ZIANG, ROY PLASTOCK, SCHAUMS OUTLINES, Chapter 3
Sectors

A sector is the portion of area that an arc creates in a circle. As shown in figure 4.8 (a), the triangular
area of the circle created by the arc is called the sector of the circle. A sector is scan-converted by using
any of the methods used for scan-converting an arc and then scan-convert the two lines forming the arc.

Assume that a sector whose center is at point (h, k) is to be scan-converted.
First, you need to scan-convert an arc from θ1 to θ2. Next, a line would be scan-
converted from (h, k) to (r cos(θ1) + h, r sin(θ1) +k). A second line would be

scan-converted from (h, k) or to (r cos(θ2) + h, r sin(θ2) +k).

4.6 Summary

• The process of representing continuous graphics objects as a collection of discrete pixels is known
as scan conversion or rasterization.
• The two methods for changing a picture’s data rate are analog method and digital method.

• Digital Differential Analyzer (DDA) algorithm is one of the incremental scan-conversion methods.
4.7 Keywords
2-D: Two-Dimensional

3-D: Three-Dimensional
Symmetrical: The two entities exhibiting equivalence among their constituents such as size, shape and
position of parts.
Tangent: The line meeting a curve or surface at a point and has same direction as curve or surface at the
point.

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