Hmmm ... I read this group now a while, and I think the treeIdea is not as
bad ...
especially the idea that not only to use cylinders but blobs for use as the
branches is important, I think ...
But there I got an Idea to offer ...

Why Use the Tree in the Geometrics Part of PoV?? Why create a Geometric
Object ???

Can't we use it as a kind of Media ???
I think this way: I just create a hollow cube, assignin' a texture with a
media. This media is computed by the new tree-Algo with will (with the right
DensityMap) show a nice tree. One Pro would be that, by adding an noise to
this, you can create a relative natural taste of it ...

But I'm sure there are enough Contras to this(just thinking on the speed).


Now it's on you, the masters, to decide about this dumb Idea of a novice ;-)

PS.: Sorry 'bout my bad english ... I'm from germany, you see...

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"Jan Walzer" <nos### [at] informatikuni-hallede> writes:

> Hmmm ... I read this group now a while, and I think the treeIdea is not as
> bad ...
[...]
> Can't we use it as a kind of Media ???

You're not the first one to come up with this idea. It has already be
phrased by Kajiya and Kay in "Rendering Fur with Three Dimensional
Textures", Computer Graphics, Volume 23, Number 3, July 1989.

I'm currently working more or less (read: less) on an implementation
of the fur that is presented in this paper. A short film of a furry
torus can be seen at http://www.povray.willhalm.de/tracegallery/ .

In my opinion, this approach has a lot of potential. Apart from fur,
I think that grass and forests can be renderered this way. Of course,
someone must first find an adequate lighting model for these objects.
However, you should be aware that this method will only work for 
distant views.

> PS.: Sorry 'bout my bad english ... I'm from germany, you see...

dito.

Thomas

-- 
http://thomas.willhalm.de/ (includes pgp key)

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> > Can't we use it as a kind of Media ???
>
> You're not the first one to come up with this idea. It has already be
> phrased by Kajiya and Kay in "Rendering Fur with Three Dimensional
> Textures", Computer Graphics, Volume 23, Number 3, July 1989.
Where to get this paper ?

[...]
> In my opinion, this approach has a lot of potential. Apart from fur,
> I think that grass and forests can be renderered this way. Of course,
> someone must first find an adequate lighting model for these objects.
> However, you should be aware that this method will only work for
> distant views.
hmmm ... but am I right, about the rendertime ...
I've thougt about the last night, and found that therefore the "steps in the
media" (or how was it called) have to be massivly increased, to get all the
branches of a high-detailed tree, don't they?
The standard for this is AFAIK 10 steps, and how can this make a good tree ?

Post a reply to this message

> I'm currently working more or less (read: less) on an implementation
> of the fur that is presented in this paper. A short film of a furry
> torus can be seen at http://www.povray.willhalm.de/tracegallery/ .
maybe there's something wrong with your link ???

Post a reply to this message

In article <387ba7f6@news.povray.org>, "Jan Walzer" 
<nos### [at] informatikuni-hallede> wrote:

> hmmm ... but am I right, about the rendertime ...
> I've thougt about the last night, and found that therefore the "steps in 
> the
> media" (or how was it called) have to be massivly increased, to get all 
> the
> branches of a high-detailed tree, don't they?
> The standard for this is AFAIK 10 steps, and how can this make a good 
> tree ?

I really think the best use of a density pattern to make a tree or grass 
would be in an isosurface, which is actually slightly similar to media 
in some ways. And their render speed is usually quite tolerable, 
although complex ones with a lot of very small details can be slow.

-- 
Chris Huff
e-mail: chr### [at] yahoocom
Web page: http://chrishuff.dhs.org/

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"Jan Walzer" <nos### [at] informatikuni-hallede> writes:

> > I'm currently working more or less (read: less) on an implementation
> > of the fur that is presented in this paper. A short film of a furry
> > torus can be seen at http://www.povray.willhalm.de/tracegallery/ .
> maybe there's something wrong with your link ???

I don't know. I tested it and it worked - and still works - fine for me.
There seems to be something wrong with the forwarding. So, try
http://www.fmi.uni-konstanz.de/~willhalm/graphics/tracegallery/
instead.

Thomas

-- 
http://thomas.willhalm.de/ (includes pgp key)

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"Jan Walzer" <nos### [at] informatikuni-hallede> writes:

> > > Can't we use it as a kind of Media ???
> >
> > You're not the first one to come up with this idea. It has already be
> > phrased by Kajiya and Kay in "Rendering Fur with Three Dimensional
> > Textures", Computer Graphics, Volume 23, Number 3, July 1989.
> Where to get this paper ?

First try the library of the university in Halle. If it's not available
there, you can get it using <insert what "Fernleihe" means in English>.
Alternatively, it may be downloadable with a credit card at www.acm.org,
because it's in a magazine that is published by the ACM (which I forgot to
mention). 
 
> [...]
> > In my opinion, this approach has a lot of potential. Apart from fur,
> > I think that grass and forests can be renderered this way. Of course,
> > someone must first find an adequate lighting model for these objects.
> > However, you should be aware that this method will only work for
> > distant views.
> hmmm ... but am I right, about the rendertime ...
> I've thougt about the last night, and found that therefore the "steps in the
> media" (or how was it called) have to be massivly increased, to get all the
> branches of a high-detailed tree, don't they?
> The standard for this is AFAIK 10 steps, and how can this make a good tree ?

I cannot speak for trees but for fur. Using media makes mainly sense, when
you don't care about details. Instead of a higly detailed image, you want
to look your fur (tree, grass, forest) good from a distance. So, you 
approximate the reflections instead of generating a lot of cylinders.

As far as I know, the number of steps is also calculated adaptively.
That's why I suspect the number of steps to be higher by default in
such applications. However, I didn't care about them too much so far.
I have tried the new sampling methods in the megapatch. They didn't
work very well in case of my furry torus.

Thomas

-- 
http://thomas.willhalm.de/ (includes pgp key)

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Chris Huff <chr### [at] yahoocom> writes:

> In article <387ba7f6@news.povray.org>, "Jan Walzer" 
> <nos### [at] informatikuni-hallede> wrote:
> 
> > hmmm ... but am I right, about the rendertime ...
> > I've thougt about the last night, and found that therefore the "steps in 
> > the
> > media" (or how was it called) have to be massivly increased, to get all 
> > the
> > branches of a high-detailed tree, don't they?
> > The standard for this is AFAIK 10 steps, and how can this make a good 
> > tree ?
> 
> I really think the best use of a density pattern to make a tree or grass 
> would be in an isosurface, which is actually slightly similar to media 
> in some ways. And their render speed is usually quite tolerable, 
> although complex ones with a lot of very small details can be slow.

I have tried to model the fur with an isosurface and failed miserably.
I don't know why this didn't work. With media however, it turned out
quite weill. For this reason, I believe that it may be worth the effort 
to try grass or needles with media.

Thomas

-- 
http://thomas.willhalm.de/ (includes pgp key)

Post a reply to this message

> > > The standard for this is AFAIK 10 steps, and how can this make a good
> > > tree ?
> >
> > I really think the best use of a density pattern to make a tree or grass
> > would be in an isosurface, which is actually slightly similar to media
> > in some ways. And their render speed is usually quite tolerable,
> > although complex ones with a lot of very small details can be slow.
>
> I have tried to model the fur with an isosurface and failed miserably.
> I don't know why this didn't work. With media however, it turned out
> quite weill. For this reason, I believe that it may be worth the effort
> to try grass or needles with media.
... and again this Object: "isosurface"
I've read a lot of this here in group, but I never heard something of this
before ...
Is it an extension of POV or have I to read for it in the standard POV-Docu?
Is it provided by any graphical frontend? I only seldom use Handcoding
...(yes, I use Moray)

But: What is an "isosurface" ? ...

PS: Don't answer if it is an RTFM-question ...

Jan

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Jan Walzer wrote:

> ... and again this Object: "isosurface"
> I've read a lot of this here in group, but I never heard something of this
> before ...
> Is it an extension of POV or have I to read for it in the standard POV-Docu?
> Is it provided by any graphical frontend? I only seldom use Handcoding
> ...(yes, I use Moray)
> 
> But: What is an "isosurface" ? ...
> 
> PS: Don't answer if it is an RTFM-question ...
> 
> Jan

An isosurface is a mathematical surface representation that conforms to a
set of predefined rules. Isosurfaces are not currently available in the
official version of POV-Ray. Isosurfaces are currently only available in
unofficial versions of the program but will most likely be included in
the next official release POV-Ray.

You can visit the original home page of the isosurface for specifics on
the subject -

http://www.public.usit.net/rsuzuki/e/povray/iso/index.html


And if you want to try using them in your work now there are currently
four platforms that you can find an updated patch that has Isosurfaces
available -

For the Windows OS -
http://nathan.kopp.com/patched.htm

For the Dos OS
http://www.sgib.co.uk/

For the Unix/Linux OS
http://www.mailbag.com/users/mtgordon/megapov.html

For the Mac OS
http://users.skynet.be/smellenbergh/main.html

-- 
Ken Tyler -  1300+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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