Labels:text | black and white OCR: (a) (b) (c) Figure 2: Curve segment inside a sector. In (a), the curve is represented by a thick dark line. Curve ventices are marked as small circles, The sector boundaries are draum as rectangles. Vertices inside the sector are marked dark, while vertices outside the sector are marked blank. The curve path for the sector is draum with a thin gray line underimposed to the curve line. Notice that two vertices outside the sector are needed in order to fully specify the curve path. These two vertices are called "off-by-one vertices." With off-by-one vertices, the curve segment can be draum as in (b). Without them, the curve could only be drawn as in (c).
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