Exercises Chapter 10

1. In the case of the Sutherland-Hodgman polygon clipping, consider what should happen if a polygon vertex is on a clipping boundary, or coincident with the vertex of the clip region. What should happen if an edge is (partially) coincident with a boundary?

2. What will happen in the Sutherland-Hodgman algorithm in the case of the polygon and clip region below?

3. In the following diagram, the shape defined by the points a,b,c,d,e,f is to be clipped to the viewing region A,B,C,D using the Sutherland-Hodgman algorithm. The order of clipping will be AB then CD then BC then DA. Give details of the result of clipping at each of these four stages and state whether the final result is correct or incorrect.

4. In the discussion of Weiler-Atherton it was assumed that the set E is notempty - that is, that there are intersections. Suppose there are none? Consider your answer with respect to polygon A of Figure 10.3.

5. If you know that only convex polygons can be sent down the graphics pipeline, what optimisation can you make to the Sutherland-Hodgman clipping algorithm?

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Last modified: Sun Jul 20 20:46:49 BST 2003