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Graphics Interchange Format  |  1997-01-13  |  56KB  |  455x348  |  4-bit (16 colors)
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OCR: Lead edge polygon M, x=18 Lead edge polygon N, x=50 Lead edge polygon M. x=100 Current edge, since it's a Active polygon list leading edge, sort polygon M into the activa polygon list Head of APL Polygon M zat x=16 is 50 Polygon J 2 at x=18 is 100 Polygon M has a nearer z at x= 18 than any polygon in the APL, so put polygon M at the top of the APt; it is the nearest surface at this pixel, hence visible. Emit a span for polygon J, starting at the x where J became visible and ending at Polygon K X=18: x=18 is the start coordinate for zat x=18 is 125 the span that will be emitted for polygon 'M when it ends on this scan line or becomes occluded If polygon M had not been at the nearest Polygon 1. polygon at >=18, it would have been inserted into thet APL al the proper z at x=18 is 500 z-sorted location, and nothing more would have been done, Figure 3: Activating a polygon when a leading edge is encountered in the AEL