>I don't know POV internal structure well, but probably you are right, 
>POV must first determine, if the ray intersects that polygon and then 
>look, if the polygon is transparent at the intersection point or not. 
>But all overhead caused by need of shooting new ray is removed (I
>don't know, how much it is, can be saved some work with etc
>bounding??).

The only cost saved is that of initializing a new RAY structure in
memory, which is tiny. However, your scheme would mean that every
time a ray-object intersection is performed, POV-Ray has to check
whether there is a mask object, and of course it increases code size
slightly. This would slow down the general case (where there is no
mask) just as much as it speeds up this particular case, and as the
general case is more common, it results in an overall slow-down.

-- 
Sufficiently advanced humour is indistinguishable from tedium.
corollary:
Humour distinguishable from tedium is insufficiently advanced.
http://surreal.istic.org/          Calm down, it's only ones and zeroes.

Post a reply to this message