Practical Algorithms for 3D Computer Graphics, 2nd Edition

26 2. Basic theory and mathematical results

practice a triangle where this happen s can be ignored because if one of its

sides has zero length, it has zero area and will therefore not be visible in a

rendered image.

3. Retur n hit code as follows:

i f ( α < −0.001 or α > 1.0 0 1 or

β < −0.001 or β > 1.001 ) miss polyg o n

i f ( (α + β) > 1.001) miss polygon b eyond edge P

1

→ P

2

i f ( α ≥ 0.0005 and α ≤ 0.9995

and β ≥ 0.0005 and β ≤ 0.9 9 9 5

and (α + β) ≤ 0.9995) inside polygon

e ls e i f (α < 0.0005) {

along edge P

0

→ P

1

i f ( β < 0.0005 ) at vertex P

0

e ls e ( i f β > 0.9995) at vertex P

1

e ls e On edge P

0

→ P

1

not near vertex

}

e ls e i f (β < 0.0005) {

along ...