Practical Algorithms for 3D Computer Graphics, 2nd Edition

102 4. Basic visualization

Pixels

Figure 4.7: Scanline fill by stroking the rows of the output raster.

Line 1

Line 0

Line 2

(x

0

, y

0

)

(x

1

, y

1

)

(x

2

, y

2

)

x

y

Scanline i

Figure 4.8: Scanline filling a t r ia n g u la r polygon.

This is the most useful filling procedure for a 3D p oly gon r en d er in g al-

gorithm because it works very efficiently for simple convex shapes. The

drawing stage in a large number of rendering algorithms is commonly per-

formed with triangles because a triangle is the simp les t polygon and it is

also planar. All triangles are convex. Quadrilaterals are easily divided into

two tr ian gles and higher order polygons are rare. In any case it