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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Attachments:
Download 'trivariates09_03_.jpg' (130 KB)

Preview of image 'trivariates09_03_.jpg'

at least it looks wonderful ... *g

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Ooh... Kinda Gugenheimy...

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"Tor Olav Kristensen" <tor### [at] hotmailcom> wrote in message
news:3CC1562E.ABA59E96@hotmail.com..

If this isn't mesh-ready in its current state, it looks to be only a step or
two away. As always, I am extremely interested in complex approximations
which only have to parse once. I can see extreme possibilities for this such
as fast-rendering landscapes which do not have the limitations of
height-fields.

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? 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? If so, can you recommend a good instruction book for the language,
and if not, can you suggest another language? 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.

 -Shay

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On Sat, 20 Apr 2002 13:51:10 +0200, Tor Olav Kristensen
<tor### [at] hotmailcom> wrote:

>
>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.)

...Microsoft Borg (tm) ?   :-P


-- 
Marc van den Dikkenberg
--
The PowerBasic Archives -- http://www.xlsior.org

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A very attractive image.  Has a nicely crafted look to it.

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Tor Olav Kristensen wrote:
> 
> 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.
> 

I must say i don't know enough about NURBS to seriously comment your
efforts, but it looks interesting.  

Are there any free modellers for NURBS that produce a usable data output? 
I think generating such things by hand is probably quite difficult for
serious modeling work.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 20 Apr. 2002 _____./\/^>_*_<^\/\.______

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AAAGH!  ATTACK OF THE XP LOGO!!!  ;-)

(Cool image, btw. :)

- Kevin R.

"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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Tank you all for very encouraging comments !


Tony:
I'm not much into art, but I understand that
Guggenheim is an art museum. And I guess that
there is/was an artist named Guggenheim. Are
any of his/her images similar to my last image ?
If so I would be very glad if you can give me
any pointers to such images.

Marc:
I've seen some Star Trek episodes. And I think
I remember something about Borgs. But I do not
remember if they are a species or if they are
a kind of cubical starships.

Shay:
A recursive POV-macro is a macro that calls
itself with modified arguments each time.

For an example, just look at my DeCasteljau
macros in this post:
http://news.povray.org/povray.text.scene-files/23250/161948/

Or my Fact() macro in this post:
http://news.povray.org/povray.text.scene-files/22698/157269/
It's not a good macro, because it fails with
high numbers of N. (I have made another non-
recursive one that performs better.)

I've been for a walk in the mountains all day,
so I'm too tired right now to think clearly
about your other questions. I'll try to answer
them tomorrow.


Christoph:
I haven not found many free NURBS modellers.
Except for Nurbana http://www.nurbana.cx
(a project that was started in 1999 and that
seems to advance very slowly) I have not
downloaded it yet, but I'll probably have a
peek at it some day.

I too have been thinking about how to import
NURBS from files (e.g. .iges -files ?) generated
by modellers. But I cannot see how POV-scripts
can gain access to information stored in such
files.

I have found that there exists a VRML NURBS
proposal;
http://www.blaxxun.com/developer/contact/3d/nurbs/overview.html
(But I have not had time to look at this yet
either.)

Here are two other links that may be related:
http://www.opennurbs.com/
http://yukon.genie.uottawa.ca/~lavoie/software/nurbs/


Kevin:
I have only used an XP PC once. But I cannot
remember how the XP logo looked. Is it a 3D
version of the usual window(s) flag ?

(Btw.: XP showed off a lot of black magic when
I tried to install an internal ISDN adapter on
it for a colleague of mine. So now I hope that
I never ever have to use a XP PC again.)


Tor Olav

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> 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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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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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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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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You may find this page useful:

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


Tor Olav

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"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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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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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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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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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.

Post a reply to this message