Ok, this is a question and a suggestion.

Is it possible, or would it not be very cool, if you could take a
primative and apply a normal modifier and have the parser perturb the
surface for you? Sort of a built in isosurface. I think it would be hard
to do and 'to expernsive.... but would be cool anyway.

With isosurfaces, what is the relationship between the bounding sphere
size and location and the resultant isosurface. I am haveing a deuce of
a time getting them to work.... ;-(


-p

--
-------------------------------------------#
Paul Daniel Jones
120 Chandlee Laboratory
Penn State University
814-865-2090
pdj### [at] psuedu

http://research.chem.psu.edu/glassgrp/paul
--------------------------------------------#

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Paul Daniel Jones wrote:
> 
> Is it possible, or would it not be very cool, if you could take a
> primative and apply a normal modifier and have the parser perturb the
> surface for you? Sort of a built in isosurface. I think it would be hard
> to do and 'to expernsive.... but would be cool anyway.
>

No, not as such. Regular primitives and isosurfaces use different methods for
finding the intersection. AFAIK it is not possible to modify the topology of the
former with an arbitrary function.

> With isosurfaces, what is the relationship between the bounding sphere
> size and location and the resultant isosurface. I am haveing a deuce of
> a time getting them to work.... ;-(
> 

If the bounding sphere/box is smaller than the isosurface, the isosurface (or
parts thereof) gets cut off. There's no other relationship. You just have to
make sure the bounding object is small enought, or conversely, the isosurface is
small enough. Remember that the isosurface is formed through points where a
function has a certain 'threshold' value.

-- 
Margus Ramst

Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg

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Paul Daniel Jones wrote:

>Is it possible, or would it not be very cool, if you could take a
>primative and apply a normal modifier and have the parser perturb the
>surface for you? Sort of a built in isosurface. I think it would be hard
>to do and 'to expernsive.... but would be cool anyway.

Maybe, turn your object into an "object pattern" (or proximity patter), 
turn that into a function. Turn your normal modifier into a function. Do 
some math (that I don't know) to make the whole thing usable by the 
Isosurface.
Then make a general macro for it, using "min- and max_extent" on the 
original object to create the contained-by box.
#macro (IsoObj, Normal) ...


Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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Margus Ramst wrote:
> 
> Paul Daniel Jones wrote:
> >
> > Is it possible, or would it not be very cool, if you could take a
> > primative and apply a normal modifier and have the parser perturb the
> > surface for you? Sort of a built in isosurface. I think it would be hard
> > to do and 'to expernsive.... but would be cool anyway.
> >
> 
> No, not as such. Regular primitives and isosurfaces use different methods for
> finding the intersection. AFAIK it is not possible to modify the topology of the
> former with an arbitrary function.

It could be done if true displacement mapping were added to the program.
Not impossible but difficult to code and yes it is expensive processor
wise.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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Paul Daniel Jones <pdj### [at] psuedu> wrote:
: a primative

  I have seen this word many times in this news server.
  What is it? I can't find it in the dictionary. Is it some kind of dialect?

  And answering your question: This has been discussed for years. It's far
from easy.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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ingo wrote:
> 
> Maybe, turn your object into an "object pattern" (or proximity patter),
> turn that into a function. Turn your normal modifier into a function. Do
> some math (that I don't know) to make the whole thing usable by the
> Isosurface.
> Then make a general macro for it, using "min- and max_extent" on the
> original object to create the contained-by box.
> #macro (IsoObj, Normal) ...
> 
> Ingo
> 

Using object pattern in an isosurface function is not such a good idea, because
it has a abrupt change at the object's surface the isosurface code does not like
at all.  You could use 'proximity', but it would be *really* slow.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/

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Christoph Hormann wrote:

>Using object pattern in an isosurface function is not such a good idea,
>because it has a abrupt change at the object's surface the isosurface
>code does not like at all.  You could use 'proximity', but it would be
>*really* slow. 

If you add or multiply (or whatever the best method is) the 'object 
pattern' function and the 'normal' function, would the changes still be 
abrupt?

Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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On 27 Oct 2000 11:14:47 -0400, Warp wrote:
>Paul Daniel Jones <pdj### [at] psuedu> wrote:
>: a primative
>
>  I have seen this word many times in this news server.
>  What is it? I can't find it in the dictionary. Is it some kind of dialect?

Try looking under "primitive."  Unless this was just a spelling flame, in
which case try looking under a rock.

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
My opinions.  Mine.  Not anyone else's.

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ingo wrote:
> 
> If you add or multiply (or whatever the best method is) the 'object
> pattern' function and the 'normal' function, would the changes still be
> abrupt?
> 

Sure it would, just at the surface (and not across some area around it), the
value changes from 0 to 1 leading to an infinite gradient. 
adding/multiplying/etc. does not help.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/

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"Paul Daniel Jones" wrote:
> Is it possible, or would it not be very cool, if you could take
> a primative and apply a normal modifier and have the parser
> perturb the surface for you? Sort of a built in isosurface.
> I think it would be hard to do and 'to expernsive....
> but would be cool anyway.

I started a similar discussion in povray.general a while ago and the
conclusion seemed to be that it's not possible. :(

Greetings,

Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated October 9)
/ Also visit http://www.povrayusers.org

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heigh! so I kant spel. wat of it?

Warp wrote:

> Paul Daniel Jones <pdj### [at] psuedu> wrote:
> : a primative
>
>   I have seen this word many times in this news server.
>   What is it? I can't find it in the dictionary. Is it some kind of dialect?
>
>   And answering your question: This has been discussed for years. It's far
> from easy.
>
> --
> main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
> ):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

--
-------------------------------------------#
Paul Daniel Jones
120 Chandlee Laboratory
Penn State University
814-865-2090
pdj### [at] psuedu

http://research.chem.psu.edu/glassgrp/paul
--------------------------------------------#

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thanks....  

-paul

Rune wrote:
> 
> "Paul Daniel Jones" wrote:
> > Is it possible, or would it not be very cool, if you could take
> > a primative and apply a normal modifier and have the parser
> > perturb the surface for you? Sort of a built in isosurface.
> > I think it would be hard to do and 'to expernsive....
> > but would be cool anyway.
> 
> I started a similar discussion in povray.general a while ago and the
> conclusion seemed to be that it's not possible. :(
> 
> Greetings,
> 
> Rune
> --
> \ Include files, tutorials, 3D images, raytracing jokes,
> / The POV Desktop Theme, and The POV-Ray Logo Contest can
> \ all be found at http://rsj.mobilixnet.dk (updated October 9)
> / Also visit http://www.povrayusers.org

-- 



--------------------------------------------------}
Paul Daniel Jones
The Pennslyvania State University

pdj### [at] psuedu
http://research.chem.psu.edu/glassgrp/paul

       C            The way is near, but men
     // \           seek it afar. It is in the
    N    N          easy things, but men seek it
    |    ||         in the difficult things.
    C    C          -Menicius
     \\  /
       C
--------------------------------------------------}

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Ken wrote:
> 
> It could be done if true displacement mapping were added to the program.
> Not impossible but difficult to code and yes it is expensive processor
> wise.
> 

However, "true displacement mapping" as used in practice, involves tessellating
the primitive and displacing the resultant mesh.
The way I understand it, performing non-uniform transformations (including
displacement mapping) on a mathematical primitive would require finding the
intersection of the primitive and a curved ray - often impossible for all
practical purposes.

-- 
Margus Ramst

Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg

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Margus Ramst wrote:
> 
> Ken wrote:
> >
> > It could be done if true displacement mapping were added to the program.
> > Not impossible but difficult to code and yes it is expensive processor
> > wise.
> >
> 
> However, "true displacement mapping" as used in practice, involves tessellating
> the primitive and displacing the resultant mesh.
> The way I understand it, performing non-uniform transformations (including
> displacement mapping) on a mathematical primitive would require finding the
> intersection of the primitive and a curved ray - often impossible for all
> practical purposes.

I'll bet Ron Parker could code it. Ron Parker can code anything if
he sets his mind to it.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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In article <39FBA606.25156DDC@pacbell.net>, lin### [at] povrayorg 
wrote:

> I'll bet Ron Parker could code it. Ron Parker can code anything if
> he sets his mind to it.

Or Nathan Kopp. And if they work together on 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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On Sat, 28 Oct 2000 21:22:30 -0700, Ken wrote:
>I'll bet Ron Parker could code it. Ron Parker can code anything if
>he sets his mind to it.

I'm more of an idea rat...

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
My opinions.  Mine.  Not anyone else's.

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Ron Parker wrote:

> I'm more of an idea rat...

The death of a legend...

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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On Sun, 29 Oct 2000 19:54:45 -0800, Ken wrote:
>
>
>Ron Parker wrote:
>
>> I'm more of an idea rat...
>
>The death of a legend...

No, no, that wasn't to say that I can't do the work, just that my role of late
has been more that of the guy who plants seeds in the minds of people who have
time to do stuff.

Besides, it was a Dilbert quote.

-- 
Ron Parker   http://www2.fwi.com/~parkerr/traces.html
My opinions.  Mine.  Not anyone else's.

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