POV-Ray : Newsgroups : povray.binaries.images : A slightly different Trivariate (130KB) Server Time
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From: Tony[B]
Subject: Re: A slightly different Trivariate (130KB)
Date: 22 Apr 2002 14:30:09
Message: <3cc456b1@news.povray.org>
> Tony:
> I'm not much into art, but I understand that
> Guggenheim is an art museum.

Exactly. :) That's what I meant. It reminded me of that museum.


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From: Shay
Subject: Re: A slightly different Trivariate (130KB)
Date: 23 Apr 2002 09:30:51
Message: <3cc5620b@news.povray.org>
Tor Olav Kristensen <tor### [at] hotmailcom> wrote in message
news:3CC364F6.F77BCFB3@hotmail.com...
>
> Shay:
> A recursive POV-macro is a macro that calls
> itself with modified arguments each time.
>

Then the answer to your question about my ever having written a recursive
macro is no. Most of the macros I write are as small as possible and perform
only one iteration. This means that I often call a macro several times in a
row.

 -Shay


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From: Tor Olav Kristensen
Subject: Re: A slightly different Trivariate (130KB)
Date: 23 Apr 2002 18:25:53
Message: <3CC5DF3D.EB8FFE17@hotmail.com>
Shay wrote:
>...
> You said in a reply in your previous mesh post that the parsing time is over
> an hour. How reasonable do you think the parsing time might be in C?
>...

During the parsing of my "A Trivariate NURBS function" image
POV-Ray had to evaluate 3 NURBS functions for each sphere (one
function for each x, y and z coordinate, because POV-Ray does
not allow for arbitrary vector functions yet).

And when the sphere grid is 80*80*80 = 512 000 spheres, then
POV-Ray has to do 1 536 000 evaluations of NURBS functions in
order to place these spheres.

The way I have chosen to build the blending functions in the
macros I posted for the NURBS functions, are quite "quick and
dirty".

The resulting blending functions are quite non optimal,
because the recursive algorithm chosen causes some of the
calculations to be repeated several times.

At the moment I'm looking into other ways of building these
functions.

If one writes a C-program and uses more optimal blending
functions, then I think (or hope ?) that its performance
will be several hundred times better.


Tor Olav


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From: Tor Olav Kristensen
Subject: Re: A slightly different Trivariate (130KB)
Date: 23 Apr 2002 19:14:41
Message: <3CC5EAAC.491D0CFE@hotmail.com>
Shay wrote:
>...
> I looked at the modeler link which you posted for me(Thanks), and it looks
> basically like a limited Pov-Ray type program with several mesh macros. I am
> considering writing such a program myself and adding a graphical interface
> which can be used to drag control points for mathematical surfaces. If the
> parsing time for even a reasonable preview is too high (your picture only
> seems to have a few thousand faces) I think I could get around this by
> having two accuracy variables for this shape. One would control the true
> accuracy and the other would control the degree to which the true points are
> subdivided. That way, a user can make changes and see some reasonable
> quality renders before a final (perhaps hours long) re-parse of all his
> objects.
> 
> Do you think that C would be the best language in which to write such a
> modeller?

Yes, either C or C++. Because they are powerful
and are widely used in the industry.


If you care for portability, then Java might be
a better (but slower ?) solution.

You should also have a look at OpenGL:

http://www.opengl.org/users/about/index.html
(I have not done that myself yet, but I hope
that I some day will find time for that.)

"The OpenGL standard has language bindings for
C, C++, Fortran, Ada, and Java."


> If so, can you recommend a good instruction book for the language,

At this page:
http://www.faqs.org/faqs/C-faq/learn/

- you'll find the answers to these questions:

14: What are the best books I can learn C from?
15: What are the best books I can learn C++ from?

I have the 2nd edition of "The C Programming Language"
by Kernighan & Ritchie. And I think it is quite good.


> and if not, can you suggest another language?

I have programmed some in Pascal. - And I like that
language very much (maybe better than C).

If you want to play with the Pascal language then I
recommend that you check out Delphi; which uses
object oriented Pascal. (I think Borland has a
personal edition which you can download for free.)

http://www.borland.com/delphi/

http://www.borland.com/kylix/
(Similar "thing" for Linux)


> I'm not sure if this is possible, but I want to make the modeler so that
> it can open Pov-Ray and render objects without the user's having to do much.

This is what Moray does, so it is possible.

http://www.stmuc.com/moray/


Tor Olav


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From: Tor Olav Kristensen
Subject: Re: A slightly different Trivariate (130KB)
Date: 23 Apr 2002 19:21:43
Message: <3CC5EC52.40A01209@hotmail.com>
You may find this page useful:

http://directory.google.com/Top/Computers/Programming/Languages/


Tor Olav


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From: Tor Olav Kristensen
Subject: Re: A slightly different Trivariate (130KB)
Date: 23 Apr 2002 19:53:53
Message: <3CC5F3DB.C08409CB@hotmail.com>
"Tony[B]" wrote:
> 
> > Tony:
> > I'm not much into art, but I understand that
> > Guggenheim is an art museum.
> 
> Exactly. :) That's what I meant. It reminded me of that museum.

OK, I think that I found some images of it:

http://www.GreatBuildings.com/buildings/Guggenheim_Bilbao.html

And I like it !


Tor Olav


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From:
Subject: Re: A slightly different Trivariate (130KB)
Date: 24 Apr 2002 03:20:06
Message: <rqmccug0ejt4ld3d2nb8gfiqlu0cst1f5h@4ax.com>
On Wed, 24 Apr 2002 00:25:01 +0200, Tor Olav Kristensen
<tor### [at] hotmailcom> wrote:

> (one
> function for each x, y and z coordinate, because POV-Ray does
> not allow for arbitrary vector functions yet).

not allow directly and not if efficent way but it is partially possible

http://news.povray.org/jltmaukpci64s7497l1qdr79asqpl6tpln@4ax.com

ABX


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From: Shay
Subject: Re: A slightly different Trivariate (130KB)
Date: 24 Apr 2002 10:20:47
Message: <3cc6bf3f$1@news.povray.org>
Thank you for all of the great information.

 -Shay

Tor Olav Kristensen <tor### [at] hotmailcom> wrote in message
news:3CC5EC52.40A01209@hotmail.com...


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From: Michael Goldshteyn
Subject: Re: A slightly different Trivariate (130KB)
Date: 25 Apr 2002 14:00:03
Message: <3cc84423@news.povray.org>
Very nice, could please post the source?

Thanks

Mike

"Tor Olav Kristensen" <tor### [at] hotmailcom> wrote in message
news:3CC1562E.ABA59E96@hotmail.com...
>
> The 3D grid of control points for this shape
> is less "disturbed" than the grid used for the
> trivariate shape in my "A Trivariate NURBS
> function" image posted here a couple of days
> ago. (The random translation of the control
> points away from a cube grid is less severe.)
>
> I have divided the trivariate into 8 subpatches
> in an attempt to show the "internals" of it.
>
> The triangles are just simple triangle{} shapes.
>
>
> Tor Olav


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From: Tor Olav Kristensen
Subject: Re: A slightly different Trivariate (130KB)
Date: 27 Apr 2002 08:17:48
Message: <3CCA968D.6145348F@hotmail.com>
Michael Goldshteyn wrote:
> 
> Very nice, could please post the source?

Thank you.

The source looks ugly now, so it needs cleaning.
- And I will post when I'm done with that.


Tor Olav


> Thanks
> 
> Mike
> 
> "Tor Olav Kristensen" <tor### [at] hotmailcom> wrote in message
> news:3CC1562E.ABA59E96@hotmail.com...
> >
> > The 3D grid of control points for this shape
> > is less "disturbed" than the grid used for the
> > trivariate shape in my "A Trivariate NURBS
> > function" image posted here a couple of days
> > ago. (The random translation of the control
> > points away from a cube grid is less severe.)
> >
> > I have divided the trivariate into 8 subpatches
> > in an attempt to show the "internals" of it.
> >
> > The triangles are just simple triangle{} shapes.


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