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Computer Graphics
The polygon is said to be concave when a line is obtained after joining the two interior points of the
polygon which lies totally inside the polygon. Where as polygon is said to be convex when there is at
least one pair of point such that the line joining the points inside the polygon does not lie completely
inside the polygon. The figure 10.1 provides a clear idea of concave polygon and figure 10.2 provides a
clear idea of convex polygon.
Figure 10.1: Concave
Polygon
Figure 10.2: Convex
Polygon
The polygon clipping can be further explained using the following two algorithms.
1. Sutherland-Hodgeman Algorithm
2. Weiler-Atherton Algorithm
Sutherland-Hodgeman Algorithm
Polygon clipping is relatively straightforward and can be easily implemented. Sutherland-Hodgeman
algorithm uses the divide and conquer strategy to solve the problem related to polygon clipping. First,
this algorithm clips the part of the polygon that is adjacent to the right or left clipping boundary. Then,
this partly clipped polygon is clipped against the top boundary and the same process is repeated for the
two remaining boundaries.
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