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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Nope. the demo runs on all computers, without outside programs.
Enjoy.

H.E. Day
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In article <3a205906@news.povray.org>, "H. E. Day" <Pov### [at] aolcom> 
wrote:

> Nope. the demo runs on all computers, without outside programs.

The demo may stand alone without requiring other software, but there is 
still the "Wintel only" part. It certainly doesn't run on all 
computers...

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

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Hi,

how we can make hairs in POV? Polygon model and extruding along a
spline..other methods?
How much memory it needs to extrude a circle along a spline?

Paul

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In article <3A21899C.C9B74D67@alpharay.de>, Paul Blaszczyk 
<3d### [at] alpharayde> wrote:

> how we can make hairs in POV? Polygon model and extruding along a
> spline..other methods?

Torus segments, sphere sweeps, blob components or spheres and 
cones/cylinders along the path of the hair...


> How much memory it needs to extrude a circle along a spline?

Depends on what you mean...if implemented as a new feature, a radius and 
a point for every control point, similar to the sphere_sweep. Otherwise, 
the memory required to hold all the objects it is made of...a bunch of 
differences each made of a torus and two planes, a mesh, a bunch of 
spheres and cylinders, a blob, a sphere sweep...

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

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Paul Blaszczyk wrote:
> 
> Hi,
> 
> how we can make hairs in POV? Polygon model and extruding along a
> spline..other methods?
> How much memory it needs to extrude a circle along a spline?

	Can it be done in the sense of realistic? One hair vice a head of is
smaller than a pixel so it won't render unless close enough. 

	What are a hundred thousand hairs on a head that can't be seen?
Actually they could be seen and show up as a mass. Parsing time over the
edge of reality though. 

	So then we look at hair on TV and in movies and in fact in daily life
as we don't see individual hairs either for the most part. 

	One of my recent failures has been to imitate a 2D graphics trick. The
trick is a 3x300 (to pick a ratio), add noise and then scale it to
300x300. That is the PhotoShop "brushed aluminum" tutorial example. 

	Scaling bumps like that doesn't quite seem to work but then a hairy
sphere isn't quite right either. Reflection, specular combinations don't
seem to give the right impression. 

	The basics of hair appear to be highlights on a stretched pattern with
highlights but it has to be an interupted highlight so it is not like a
smooth surface highlight. 

	But after that, I can't see the least way to get even the simplest
hairstyles right from the hairdresser perfect out of it and then only
women's styles that cover the front hairline with bangs, even if I get
it working. 

-- 
It must be terrible to be bound by the past 
or in hopes of the future. 
	-- The Iron Webmaster, 169

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Chris Huff <chr### [at] maccom> wrote:
: It certainly doesn't run on all computers...

  For some people PC is the only existing computer... ;)

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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Warp wrote:
> 
> Chris Huff <chr### [at] maccom> wrote:
> : It certainly doesn't run on all computers...
> 
>   For some people PC is the only existing computer... ;)

You mean to suggest that there is a truly viable alternative ?   ;~}

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Ken <tyl### [at] pacbellnet> wrote:
: You mean to suggest that there is a truly viable alternative ?   ;~}

  It depends on what you are doing.

  For home-use, PC has the best price/efficiency rate.
  However, in many places they don't use PCs but other computers (Sparc
servers, Alpha servers, Crays, SGIs...). For a reason.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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"H. E. Day" wrote:
> 
> Pov Programmers!!
> You might want to check out this link:
> http://www.joealter.com/software.htm
> This system is based on z-buffer rendering, but I don't know if it could be
> appiled to Pov.  It does look very versitile.
> Also look at:
> http://www.joealter.com/shave/overview.htm
> Neat, huh?
> I want it!!!! :)

	Someone hit the wrong button and sent email rather than posted. They
may want to post it here. 

	A summary of the point made (pardon if not) was the Coca-Cola polar
bear was realistic modeling and massive computation. 

	Thinking about that I had a related problem on my truck in IRTC History
and in the Halloween competitions. Lines fell below the POV pixel limit
for the image size. I solved that by rendering a larger size and then
making it smaller in Photoshop. I presume increasing the sampling or
some trick in POV would have accomplished the same objective. 

	That may be a route to getting "correctly" modeled hair to look like
hair. It certainly took a lot longer that way. 

-- 
If you render too quickly you may miss some pixels.
	-- The Iron Webmaster, 256

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