Tessellating complex polygons in modeling coordinates

Details Tessellating complex polygons in modeling coordinates Tessellating complex polygons in modeling coordinates

1989-11-21

1994-01-04

Harkcom, Gary V.

395119, 395133, G06F 1562

Patent

active

052767833

ABSTRACT:
A method, in a computer graphics system, manipulates the vertices contained within a group of possibly self intersecting, free space, over lapping polygons, into simple, convex polygons. A normal axis to the complex polygon is determined such that the surface of the polygon is viewed along this normal axis. The polygon surface is then bounded by a rectangle and subdivided into a group of slabs, or smaller rectangles, each rectangular slab being bounded by a pair of interior vertices of the complex polygon. An active edge table is used to store values corresponding to the edges crossing through the slabs, which are used to determine if these edges cross are another at any point within the slab. If a crossing point does exist, the slabs are divided at the crossing point into rectangular sub-slabs until it is determined that no edge intersects another edge within the sub-slabs, of the original slab being considered. At this point, the edges contained within the rectangular slabs can be viewed as simple polygons, or trapezoids which can be filled by a conventional graphics adapter and then displayed.

REFERENCES:
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Computer & Graphics, vol. 11, No. 4, 1987, J. R. Rankin, "A Note on Multi-Polygon Area Filling", FIG. 2.

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