Practical Algorithms for 3D Computer Graphics, 2nd Edition

170 5. Realistic visualization

DoRay( p,

ˆ

d, s ) {

Find the identity of the po lyg o n , k, that intersects the ray p + µ

ˆ

d

at p

i

and is closest to p.

Calculate surface color s

s

for polygon k at p

i

ˆ

d

t

use procedural texture or image map if required

If the material properties of k indicate that it is partially

reflective or transparent th en cast extra rays .

If reflective get reflective direction

ˆ

d

r

DoRay( p

i

,

ˆ

d

r

, s

r

) ;

If transparent get transparent direction

ˆ

d

t

DoRay( p

i

,

ˆ

d

t

, s

t

)

Get surface nor ma l, ˆn

i

at p

i

, use Phong’s interpolation

and any proced u r a l or bump mapping if necessary.

From p

i

send feeler ray to each light sou r c e. Test every po lyg o n