In article <01c05674$d4b80a40$617889d0@daysix>, "H. E. Day" 
<Pov### [at] aolcom> wrote:

> Could the vista buffer be used in such a way? 

No...the vista buffer is entirely unrelated. It is a bounding feature, 
kind of a bounding for bounding boxes, and has nothing to do with 
scan-line algorithms, it wouldn't be any help in rendering hair.


> Perhaps a z-buffer post_process op?  I wasn't suggesting that you do 
> this *while* the render runs, but afterwards. 

A post_process would be extremely limited...no reflections, the hair 
either wouldn't be applied to objects behind transparent objects and 
wouldn't show up around the edges of an object completely covering the 
"hairy" object, or it would be applied over everything giving a 
completely unrealistic and ugly result, etc...imagine your poodle 
walking behind a pane of glass and turning into a bunch of spheres and 
cones.
Also, it would basically require implementing a fairly advanced scanline 
renderer as a post_process filter, as well as various other adjustments 
so the needed information still exists at that stage. Might as well 
write a new renderer...


> As for the memory hit, only one hair is in memory at a time, so there 
> is no large memory hit. 

If done one at a time, you trade time for memory, since you have to 
recalculate the hairs for every pixel(storing enough hairs is obviously 
not feasible, even with sharing mesh data...). It might be possible to 
partly compensate with some kind of bounding scheme, so only hairs that 
might be visible are tested, but it will still be a significant cost. A 
media-like rendering algorithm still seems to be the best option, though 
it would be slow. Maybe a new media type, maybe a completely different 
feature.


> Also, you might want to download the demo.  It really rocks, and 
> gives a better idea of how these hairs are made.

"Intel Only - Win95, Win98, WinNT - LW 5.5,5.6,5.7,6.0,6.5"

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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