I've recently accessed this newsgroup after 2(?) year absence.
And I surprised that the ver 3.5 beta has been released!

I'm so glad that the isosurface and function pattern features are
included in ver 3.5 and those were improved nicely from the isosurface
patch.
The documentation is great, too.  Thanks POV-team and patch supporters.

I wrote the first isosurface code in PC-FORTRAN about 15 years ago.
I could not imagine today's situation at that time.

POV-Ray 3.5 would be useful not only for hobby, but also for scientific
research, education, etc.  I want to write some know-hows on my web-page.
(Well, I'm not sure I can get enough time to write them.)

Ryoichi Suzuki
---------------------------------------------------------------------
My e-mail address was changed.  The new address is r-s### [at] aistgojp.

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Isosurfaces are certainly a very handy feature.

  Could you explain how they are raytraced? I have just very vague notions
about it, but I don't know any details. It would be interesting to know the
algorithm to raytrace isosurfaces.

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

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"R. Suzuki" wrote:

> I wrote the first isosurface code in PC-FORTRAN about 15 years ago.
> I could not imagine today's situation at that time.

I'd like to thank you personally for introducing isosurfaces in Povray. I
"discovered" your patch back in 1997 and was immediately hooked. It changed
the way I used Povray after that because they offered a creative flexibility
the standard version didn't have. Actually, the second version of my web site
in 1998 was completely designed around isosurfaces and most of my images have
used them since, first through your patch, then with the Superpatch, Megapov
and now Povray 3.5.

Gilles Tran

--

**********************
http://www.oyonale.com
**********************
Graphic experiments
Pov-ray gallery

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(Speaking in what little Nippongo he knows.)

Domo arigato gozaimasu!

You have, without a doubt, contributed one of the most important things that
currently make up POV-Ray. I have become utterly dependant on them for
expressing myself with POV. I would be crippled without them. Thank you so
much! It's wonderful to see you on the newsgroups. :)

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Let me also add my sincere thanks for your work in this area. I have just
had a 9-minute animation presented at a major graphics conference in the US
that consisted entirely of morphing isosurfaces. The credit is all yours!
Best,
Dennis
"R. Suzuki" <r-s### [at] aistgojp> wrote in message
news:3b97561c@news.povray.org...
> I've recently accessed this newsgroup after 2(?) year absence.
> And I surprised that the ver 3.5 beta has been released!
>
> I'm so glad that the isosurface and function pattern features are
> included in ver 3.5 and those were improved nicely from the isosurface
> patch.
> The documentation is great, too.  Thanks POV-team and patch supporters.
>
> I wrote the first isosurface code in PC-FORTRAN about 15 years ago.
> I could not imagine today's situation at that time.
>
> POV-Ray 3.5 would be useful not only for hobby, but also for scientific
> research, education, etc.  I want to write some know-hows on my web-page.
> (Well, I'm not sure I can get enough time to write them.)
>
> Ryoichi Suzuki
> ---------------------------------------------------------------------
> My e-mail address was changed.  The new address is r-s### [at] aistgojp.
>
>

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In article <3b97602b@news.povray.org> , Warp <war### [at] tagpovrayorg>  wrote:

>   Isosurfaces are certainly a very handy feature.
>
>   Could you explain how they are raytraced? I have just very vague notions
> about it, but I don't know any details. It would be interesting to know the
> algorithm to raytrace isosurfaces.

I would like to add to this question:

Maybe there are any literature references on how the algorithm works?  Or
any other detailed description?  As I am the person guilty of making nearly
all the changes (in isosurfaces, Ron did the parametric stuff) without
perfectly understanding what is going on, it would be really nice to know
what exactly I was tweaking.

In particular I had been playing (with not much success) with automatic
max_gradient finding without evaluate and other similar tricks that would
make it easier and still be fast to render isosurfaces right the first
time...

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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"Thorsten Froehlich" <tho### [at] trfde> wrote:
> Maybe there are any literature references on how the algorithm works?  
>Or any other detailed description? 

I have submitted a paper of the algorithm ("method 2" in the patches) 
 to an international workshop of implicit surfaces.  
But that paper was rejected. 
This would be because I do not have any background in computer 
science (my major research field is materials science).

Followings are short description of the algorithm.  It is very
simple.  If someone interested in details, I can send the rejected 
paper by e-mail.

 -----------------------------------------------------------
 THE METHOD OF ISOSURFACE SEARCHING
 -----------------------------------------------------------
The isosurface searching is a recursive subdivision method.  
In the first step, POV-Ray calculate the function values F(d_1) 
and F(d_2) on the ray , where d is the distance from the initial 
point and d_1<d_2.

If there is a possibility of isosurface between d_1 and d_2,
POV-Ray will calculate function value at another point 'd_3' 
on the ray between the two points 'd_1' and 'd_2'.  

The possibility is evaluated with the values F(d_1), F(d_2), 
the length from d_1 to d_2, and MAX_GRADIENT.

Then, if there is a possibility of isosurface between 'd_1' and 
'd_3', POV-Ray calculate another point between 'd_1' and 'd_3'.  
If there is no possibility between 'd_1' and 'd_3', POV-Ray 
looks for another point between 'd_3' and 'd_2', and so on.   

These calculations are carried out recursively until 
(d_n-d_n')<"ACCURACY".

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"R. Suzuki" <r-s### [at] aistgojp> wrote
> "Thorsten Froehlich" <tho### [at] trfde> wrote:
> > Maybe there are any literature references on how the algorithm works?
> >Or any other detailed description?
>  ...
>  [THE METHOD OF ISOSURFACE SEARCHING]
> These calculations are carried out recursively until
> (d_n-d_n')<"ACCURACY".



Sounds logical ... ;)

--
Jan Walzer <jan### [at] lzernet>

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"R. Suzuki" <r-s### [at] aistgojp> wrote :
>
> I wrote the first isosurface code in PC-FORTRAN about 15 years ago.

    So -you- are the one who makes me stay up late at night!

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