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  parabola object in POV (Message 1 to 10 of 10)  
From: Matthew Bennett
Subject: parabola object in POV
Date: 20 Aug 1998 09:11:56
Message: <01bdcc33$b7c23b40$1d3063c3@mrbcomp>
I know Polyray has this object.. it wouldn't be too hard to add this to POV
3.1 would it?

Just a thought..

Matt

-- 
Computers do what you *tell* them to do, not what you *want* them to do.


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From: Lance Birch
Subject: Re: parabola object in POV
Date: 20 Aug 1998 09:38:11
Message: <35dc18b3.0@news.povray.org>
Can't you use a quartic or quadric or something?  I don't know, check in
shapesq.inc?  Someone else may have a more precise answer on this.

--
Lance Birch
The Zone - http://come.to/the.zone --- SITE REDESIGN!!!
Remove the smiley to e-mail.


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From: Nieminen Mika
Subject: Re: parabola object in POV
Date: 20 Aug 1998 10:34:20
Message: <35dc25dc.0@news.povray.org>
Matthew Bennett <ben### [at] btinternetcom> wrote:
: I know Polyray has this object.. it wouldn't be too hard to add this to POV
: 3.1 would it?

  See the help about the poly object.

-- 
                                                              - Warp. -


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From: JK
Subject: Re: parabola object in POV
Date: 25 Aug 1998 11:10:33
Message: <35E2C4C4.3847632A@hotmail.com>
Matthew Bennett wrote:

> I know Polyray has this object.. it wouldn't be too hard to add this to POV
> 3.1 would it?
>
> Just a thought..
>
> Matt
>
> --
> Computers do what you *tell* them to do, not what you *want* them to do.

What do you want this 'parabola' object to look like exactly? I've noticed that
there are (almost) always several ways to solve a problem in POV script, so the
description parabola object isn't sufficient for me to think of something here
right away.Can't you be a bit more specific?

JK
http://surf.to/jkhome <--- UPDATED RECENTLY


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From: Nieminen Mika
Subject: Re: parabola object in POV
Date: 25 Aug 1998 12:17:24
Message: <35e2d584.0@news.povray.org>
JK <kla### [at] hotmailcom> wrote:
: What do you want this 'parabola' object to look like exactly? I've noticed that
: there are (almost) always several ways to solve a problem in POV script, so the
: description parabola object isn't sufficient for me to think of something here
: right away.Can't you be a bit more specific?

  I think that what he means is a paraboloid, which can be defined with the
function f(x,y)=x^2+y^2
  This can be easyly achieved in povray with the poly object.

-- 
                                                              - Warp. -


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From: JK
Subject: Re: parabola object in POV
Date: 25 Aug 1998 18:48:03
Message: <35E32FEE.DC3CF3DA@hotmail.com>
<HTML>
 

<P>Nieminen Mika wrote:
<BLOCKQUOTE TYPE=CITE>JK <kla### [at] hotmailcom> wrote:
<BR>: What do you want this 'parabola' object to look like exactly? I've
noticed that
<BR>: there are (almost) always several ways to solve a problem in POV
script, so the
<BR>: description parabola object isn't sufficient for me to think of something
here
<BR>: right away.Can't you be a bit more specific?

<P>  I think that what he means is a paraboloid, which can be defined
with the
<BR>function f(x,y)=x^2+y^2
<BR>  This can be easyly achieved in povray with the poly object.

<P>--
<BR>                                                            
- Warp. -</BLOCKQUOTE>
THE WONDERS OF THE POVRAY DOCUMENTATION
<BR>Lesson 1
<BR>by JK

<P>7.5.4.3 Quadric

<P>Quadric surfaces can produce shapes like ellipsoids, spheres, cones,
cylinders, PARABOLOIDS (dish shapes) and hyperboloids (saddle or hourglass
shapes). Note that you do not confuse quaDRic with quaRTic. A quadric is
a 2nd order polynomial while a quartic is 4th order. Quadrics render much
faster and are less error-prone.

<P>A quadric is defined in POV-Ray by
<BR> 

<P>  quadric { <A,B,C>, <D,E,F>, <G,H,I>, J }
<BR> 

<P>where A through J are float expressions that define a surface of x,
y, z points which satisfy the equation
<BR> 

<P>  A x^2   + B y^2   + C z^2 +
<BR>  D xy    + E xz    + F yz +
<BR>  G x     + H y     +
I z    + J = 0

<P>.....
<BR>and so on.
<BR>It's all there. Don't think too much on the math, just begin.
<BR>Yesyes, you're welcome.

<P>JK
<BR>--
<BR> <A HREF="http://surf.to/jkhome">Visit my newly updated homepage!</A></HTML>


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From: Ron Parker
Subject: Re: parabola object in POV
Date: 25 Aug 1998 19:06:12
Message: <35e33554.0@news.povray.org>
On Tue, 25 Aug 1998 23:43:10 +0200, JK <kla### [at] hotmailcom> wrote:
><HTML>
...
>THE WONDERS OF THE POVRAY DOCUMENTATION
><BR>Lesson 1
><BR>by JK
...
><BR> <A HREF="http://surf.to/jkhome">Visit my newly updated homepage!</A></HTML>

THE WONDERS OF USENET
Lesson 1
by parkrrrr

Usenet is wonderful because it isn't the World Wide Web and doesn't want to
be.  This means that, if everyone is doing his or her job, you will never
find a Usenet post that doesn't work with your newsreader, as opposed to the
World Wide Web, where every other site has Java or Javascript or some stupid
plugin that only works with one or two browsers.  

Unfortunately, some Web browser manufacturers seem to think that news:// is 
just another way of saying http://, and they give their technically 
unsophisticated users access to HTML editing tools that allow them to post
the resulting HTML gibberish to the plain-text-only Usenet.

So help keep Usenet wonderful, and don't post HTML.  Better yet, avoid any
"newsreader" that allows you to post HTML, since doing so, along with 
threading by subject line, is one of the signs of a newsreader author who 
doesn't understand Usenet.

While you're at it, shun any editor that creates superfluous non-breaking
spaces, as those are a sign of an editor author who doesn't understand HTML,
either.


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From: JK
Subject: Re: HTML in Usenet
Date: 26 Aug 1998 18:20:27
Message: <35E47B04.911B162D@hotmail.com>
Greetings all
An apology is in place. The fact is, I didn't pay attention when I posted the article
and
that's why it 'became' HTML. I totally agree that it's not necessary (and often even
irritating) to run upon a hypertext-file in usenet. Let's all sing along with Ron
Parker:
"Don't use html on usenet, lalala"

JK


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From: J  L  Rose
Subject: Re: parabola object in POV
Date: 7 Oct 1998 01:00:19
Message: <361ABD18.152C@spamBgone.nbnet.nb.ca>
Matthew Bennett wrote:
> 
> I know Polyray has this object.. it wouldn't be too hard to add this to POV
> 3.1 would it?

Have you tried the Link Include File from 
http://www.geocities.com/SiliconValley/Lakes/1434/linkinc.html ?

I haven't tried using it myself yet, but it might be useful. Here's what
they 
say about it...

    " The Link Include File allows you to connect any two points
      with a hanging chain made of any object, with complete control 
      over looseness, twisting, etc."

Now, I would hope that this Link Include file generates caternaries, if
they are 
to look like hanging cables, but perhaps it can be modified to produce a 
parabolic curve. Or, maybe a caternary is close enough?

-jr- 
**********************************************
* Delete "spamBgone." to get my real address *
**********************************************


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From: Chris Colefax
Subject: Re: parabola object in POV
Date: 16 Oct 1998 00:56:54
Message: <3626C80B.14525D11@geocities.com>
Matthew Bennett wrote:
> I know Polyray has this object.. it wouldn't be too hard to add this to POV
> 3.1 would it?

J. L. Rose wrote:
> Have you tried the Link Include File from
> http://www.geocities.com/SiliconValley/Lakes/1434/linkinc.html ?
> 
> I haven't tried using it myself yet, but it might be useful. Here's what
> they
> say about it...
> 
>     " The Link Include File allows you to connect any two points
>       with a hanging chain made of any object, with complete control
>       over looseness, twisting, etc."
> 
> Now, I would hope that this Link Include file generates caternaries, if
> they are
> to look like hanging cables, but perhaps it can be modified to produce a
> parabolic curve. Or, maybe a caternary is close enough?

Regrettably, you must hope in vain - the Link Include File currently
does produce parabolic chains, not catenaries.  However, I am currently
updating the file to properly produce the latter curves for the chain,
and also to allow more general linking between points and lists of
points (so not only hanging chains can be created).  My sincerest
apologies to those who expected a little more realism ... I'm working on
it!


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