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"Vahur Krouverk" <vah### [at] aetec ee> wrote :L
>
> No, I wrote that! :-) Yes, it is isosurface, like this (POVMan 0.7 is
> required for running it, more complete example comes with
> documentation):
>
> #declare xyf=function{
> shader{
> shader_file "menger.slp"
> "rec_depth" 20
> }
> }
> isosurface {
> function {
> xyf
> }
> contained_by { box { -1.0,1.0 } }
But is it a fractal isosurface or a fractal shader? Seems like a shader
to me, not knowing anything about shaders.
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Bill DeWitt wrote:
>
> But is it a fractal isosurface or a fractal shader? Seems like a shader
> to me, not knowing anything about shaders.
Shader is probably not the best word for describing this. In version 0.7
I add feature, which allows to use shading language constructs and
virtual machine (which was created for shader byte-code execution) for
computing potential values for isosurfaces. So basically one can write
iso functions in C-like syntax, byte-compile them and use in iso-surface
calculation. As it appears, this works generally faster (2-5 times,
depending from complexity), than functions, which are written directly
in POV-Ray "language". And one can use more advanced features, such as
loops, temporary variables, etc.
Of course shader functions are slower, than built-in (i.e. hard-coded in
source code) iso-functions, about the same margin (2-5 times).
More about this is again in POVMan documentation.
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> > Thus, better and better approximations would tend to a more and more
> > opaque object which take longer and longer to render. I'd say; skip
> > the transparency. :)
>
> Um, with better approximations, the volume the ray passes through will
> decrease, and the sponge will become more and more *transparent*. You
> will get a fainter and fainter image of the sponge, until it is
> invisible. But as I said above, I'm only interested in an approximation,
> maybe 3-5 levels...a real sponge would be impossible.
I'd have thought that would depend on the material being used to make
said sponge? With a transparent but reflective material, surely internal
reflections would build up to the point where they would overpower and
obscure any view through the sponge?
I could be wrong though...
Bye for now,
Jamie.
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"Vahur Krouverk" <vah### [at] aetecee> wrote :
>
> So basically one can write
> iso functions in C-like syntax, byte-compile them and use in iso-surface
> calculation.
Ah, now I see. Thanks
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In article <MPG.1517399eed9bd1a989897@news.povray.org>,
jam### [at] ntlworldcom (Jamie Davison) wrote:
> I'd have thought that would depend on the material being used to make
> said sponge? With a transparent but reflective material, surely internal
> reflections would build up to the point where they would overpower and
> obscure any view through the sponge?
Well, I was specifically talking about transparent sponges, but I think
that the cross-section area of the sponge will tend toward 0 as the
surface area tends toward infinity, so a ray (or in the real world, a
photon) wouldn't be able to hit a perfect sponge, and would just pass
through it.
--
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/
<><
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In article <3aad1a13@news.povray.org>, "Bill DeWitt"
<bde### [at] cflrrcom> wrote:
> But is it a fractal isosurface or a fractal shader? Seems like a
> shader to me, not knowing anything about shaders.
It's a fractal isosurface using a fractal shader as a function. It's no
more a shader than an isosurface that uses a pigment function is a
pigment. The object is an isosurface, defined as all points where a
function is equal to a threshold value...the way the function is
generated doesn't matter.
--
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/
<><
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"Chris Huff" <chr### [at] maccom> wrote in message
news:chrishuff-012D20.18015012032001@news.povray.org...
> In article <3aad1a13@news.povray.org>, "Bill DeWitt"
> <bde### [at] cflrrcom> wrote:
>
> > But is it a fractal isosurface or a fractal shader? Seems like a
> > shader to me, not knowing anything about shaders.
>
> It's a fractal isosurface using a fractal shader as a function. It's no
> more a shader than an isosurface that uses a pigment function is a
> pigment. The object is an isosurface, defined as all points where a
> function is equal to a threshold value...the way the function is
> generated doesn't matter.
Right. I got that, thanks.
But I am still hoping that someone will make a fractal or pseudo-fractal
isosurface... as well as a good isosurface tree.
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In article <3aad6b4e$1@news.povray.org>, "Bill DeWitt"
<bde### [at] cflrrcom> wrote:
> But I am still hoping that someone will make a fractal or
> pseudo-fractal isosurface...
What's wrong with the Menger sponge isosurface?
> as well as a good isosurface tree.
This would probably be unuseably slow and unwieldly at a complexity high
enough for it to look like a tree. You might be able to do it with the
blob pattern in a pigment function, though...
--
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/
<><
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"Chris Huff" <chr### [at] maccom> wrote in message
news:chrishuff-947071.22170012032001@news.povray.org...
> In article <3aad6b4e$1@news.povray.org>, "Bill DeWitt"
> <bde### [at] cflrrcom> wrote:
>
> > But I am still hoping that someone will make a fractal or
> > pseudo-fractal isosurface...
>
> What's wrong with the Menger sponge isosurface?
Doesn't it need the PovMan version to run? I just barely am willing to
go with the MegaPov.
> > as well as a good isosurface tree.
>
> This would probably be unuseably slow and unwieldly at a complexity high
> enough for it to look like a tree. You might be able to do it with the
> blob pattern in a pigment function, though...
It's the principal of the thing.
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On 2001-03-10 12:23, Chris Huff <chr### [at] maccom> wrote:
>In article <3AA8E44A.6218AF06@stress.uio.no>, Simen Kvaal
><sim### [at] stressuiono> wrote:
>
>> Thus, better and better approximations would tend to a more and more
>> opaque object which take longer and longer to render. I'd say; skip
>> the transparency. :)
>
>Um, with better approximations, the volume the ray passes through will
>decrease, and the sponge will become more and more *transparent*. You
>will get a fainter and fainter image of the sponge, until it is
>invisible. But as I said above, I'm only interested in an approximation,
>maybe 3-5 levels...a real sponge would be impossible.
I have started one at 4 levels (CSG, no isosurface), but it seems that
this will take a few days (or weeks) to render. At two levels, the
transparent sponge looks rather boring, but the histogram has a mildly
interesting, space-ship-like look, so I'm posting that instead:
Post a reply to this message
Attachments:
Download 'menger-2-t5-h.jpg' (52 KB)
Preview of image 'menger-2-t5-h.jpg'
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