POV-Ray : Newsgroups : povray.advanced-users : Using lathe or SOR with an elliptical object Server Time
29 Jul 2024 00:34:22 EDT (-0400)
  Using lathe or SOR with an elliptical object (Message 1 to 5 of 5)  
From: HenryW
Subject: Using lathe or SOR with an elliptical object
Date: 20 Aug 2003 15:15:01
Message: <web.3f43c86f4e495bb8aa8c3f990@news.povray.org>
Hi,

I've been working on a POV model of a football stadium:

http://www.henrywagner.org/povray/images/POPMart2.htm
http://www.henrywagner.org/povray/images/POPMart3.htm

Currently the model is generated using the POV scripting syntax to generate
the stadium out of triangles in the shape of an ellipse. As I add more
details, the number of triangles is getting out of control. Today it hit
me, I could just define the points that make up the profile and "sweep" the
stadium out with lathe or sor, but I haven't been able to figure out how to
create the elliptical shape. One idea is to create a spherical stadium and
use "scale" to stretch it along one axis, but I don't think that will look
right. Is there away to sweep an object along an elliptical path? Any other
ideas of how to speed this up?


Henry


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From: Hughes, B 
Subject: Re: Using lathe or SOR with an elliptical object
Date: 22 Aug 2003 05:56:20
Message: <3f45e8c4@news.povray.org>
"HenryW" <pov### [at] henrywagnerorg> wrote in message
news:web.3f43c86f4e495bb8aa8c3f990@news.povray.org...
>
> I've been working on a POV model of a football stadium:
>
> http://www.henrywagner.org/povray/images/POPMart2.htm
> http://www.henrywagner.org/povray/images/POPMart3.htm
>
> Currently the model is generated using the POV scripting syntax to
generate
> the stadium out of triangles in the shape of an ellipse. As I add more
> details, the number of triangles is getting out of control. Today it hit
> me, I could just define the points that make up the profile and "sweep"
the
> stadium out with lathe or sor, but I haven't been able to figure out how
to
> create the elliptical shape. One idea is to create a spherical stadium and
> use "scale" to stretch it along one axis, but I don't think that will look
> right. Is there away to sweep an object along an elliptical path? Any
other
> ideas of how to speed this up?

I passed this message up before thinking someone would give you some kind of
answer before now. I was thinking perhaps something Tor Olav Kristensen has
done in the past might help. Mainly because he's done some great things with
manipulating POV-Ray objects. Unfortunately I'm not finding the exact thing
to show you. Only this:

http://news.povray.org/povray.general/23254/

But there's also 'prism', which could be plotted out into a ellipse and be
made conical at the same time. Might take a little learning if you're
unfamiliar with it but that would be my best suggestion.

Well, maybe you can adjust this one:

// stadium
prism {
  conic_sweep
  cubic_spline
  0.5,         // height 1
   1,         // height 2
  22,           // number of points
/* now the uv vectors */
// inner
  < -0.5, -1.5>*0.9,
  < 0,  -2>*0.9,
  < 1, -1.5>*0.9,
  < 1.25,  0>*0.9,
  < 1,  1.5>*0.9,
  < 0,  2>*0.9,
  < -1,  1.5>*0.9,
  < -1.25, 0>*0.9,
  < -1,  -1.5>*0.9,
  < 0, -2>*0.9,
  < 0.5,-1.5>*0.9,
// outer
  < -0.5, -1.5>,
  < 0,  -2>,
  < 1, -1>,
  < 1.25,  0>,
  < 1,  1>,
  < 0,  2>,
  < -1,  1>,
  < -1.25, 0>,
  < -1,  -1>,
  < 0, -2>,
  < 0.5,-1.5>
     pigment {rgb 1}
scale <1,0.667,1>
}


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From: gonzo
Subject: Re: Using lathe or SOR with an elliptical object
Date: 22 Aug 2003 14:35:01
Message: <web.3f4661b438fa04f1a0c272b50@news.povray.org>
Hughes, B. wrote:
>"HenryW" <pov### [at] henrywagnerorg> wrote in message
>news:web.3f43c86f4e495bb8aa8c3f990[at]news.povray.org...

>> Currently the model is generated using the POV scripting syntax to
>generate
>> the stadium out of triangles in the shape of an ellipse. As I add more
>> details, the number of triangles is getting out of control. Today it hit
>> me, I could just define the points that make up the profile and "sweep"
>the
>> stadium out with lathe or sor, but I haven't been able to figure out how
>to
>> create the elliptical shape.
<snip>

>But there's also 'prism', which could be plotted out into a ellipse and be
>made conical at the same time. Might take a little learning if you're
>unfamiliar with it but that would be my best suggestion.
>


Or maybe a combination of the two... Make spline of your profile, then make
a lathe object and union it with prisms made from the same spline. Prism
requires a closed spline so you probably have to use lathe rather than SOR.

RG


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From: HenryW
Subject: Re: Using lathe or SOR with an elliptical object
Date: 29 Aug 2003 19:15:01
Message: <web.3f4fddba38fa04f1aa8c3f990@news.povray.org>
gonzo wrote:
>Hughes, B. wrote:
>>"HenryW" <pov### [at] henrywagnerorg> wrote in message
>>news:web.3f43c86f4e495bb8aa8c3f990[at]news.povray.org...
>
>>> Currently the model is generated using the POV scripting syntax to
>>generate
>>> the stadium out of triangles in the shape of an ellipse. As I add more
>>> details, the number of triangles is getting out of control. Today it hit
>>> me, I could just define the points that make up the profile and "sweep"
>>the
>>> stadium out with lathe or sor, but I haven't been able to figure out how
>>to
>>> create the elliptical shape.
><snip>
>
>>But there's also 'prism', which could be plotted out into a ellipse and be
>>made conical at the same time. Might take a little learning if you're
>>unfamiliar with it but that would be my best suggestion.
>>
>
>
>Or maybe a combination of the two... Make spline of your profile, then make
>a lathe object and union it with prisms made from the same spline. Prism
>requires a closed spline so you probably have to use lathe rather than SOR.
>
>RG
>

Thanks for the tips! Currently I'm working on the triangle based version,
though I think I'm going to need more memory ;-)


Henry


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From: David Wallace
Subject: Re: Using lathe or SOR with an elliptical object
Date: 5 Sep 2003 14:46:17
Message: <3f58d9f9@news.povray.org>
Would scaling a traditional SOR be acceptable?

"HenryW" <pov### [at] henrywagnerorg> wrote in message
news:web.3f43c86f4e495bb8aa8c3f990@news.povray.org...
> Hi,
>
> I've been working on a POV model of a football stadium:
>
> http://www.henrywagner.org/povray/images/POPMart2.htm
> http://www.henrywagner.org/povray/images/POPMart3.htm
>
> Currently the model is generated using the POV scripting syntax to
generate
> the stadium out of triangles in the shape of an ellipse. As I add more
> details, the number of triangles is getting out of control. Today it hit
> me, I could just define the points that make up the profile and "sweep"
the
> stadium out with lathe or sor, but I haven't been able to figure out how
to
> create the elliptical shape. One idea is to create a spherical stadium and
> use "scale" to stretch it along one axis, but I don't think that will look
> right. Is there away to sweep an object along an elliptical path? Any
other
> ideas of how to speed this up?
>
>
> Henry
>


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