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  Concerning fresnel lenses (Message 1 to 5 of 5)  
From: Killroy Quartermaine
Subject: Concerning fresnel lenses
Date: 11 Jul 2008 01:05:00
Message: <web.4876e95722efee734cdc498c0@news.povray.org>
So I was thinking about modelling a fresnel lens using CSG, and I have two
questions.

1. Is there any reason why a fresnel lens wouldn't actually work in POVRay?

2. Because of the way they're built, what I need is torii, except instead of
round, I need them to be diamond-shaped. like, uh, for the second value of
"round". Is there any way to do this without going beyond the realm of
primitives? I'm not comfortable enough with light and finishes and whatnot to
get into making any kind of complex base shapes yet.


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From: Charles C
Subject: Re: Concerning fresnel lenses
Date: 11 Jul 2008 03:27:11
Message: <48770b4f@news.povray.org>
Killroy Quartermaine wrote:
> 2. Because of the way they're built, what I need is torii, except instead of
> round, I need them to be diamond-shaped. like, uh, for the second value of
> "round". Is there any way to do this without going beyond the realm of
> primitives? I'm not comfortable enough with light and finishes and whatnot to
> get into making any kind of complex base shapes yet.

I bet your best bet is going to be a lathe with a linear spline.
Charles


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From: SharkD
Subject: Re: Concerning fresnel lenses
Date: 11 Jul 2008 04:10:01
Message: <web.48771449d872648f9e76339c0@news.povray.org>
"Killroy Quartermaine" <iam### [at] yahoocom> wrote:
> So I was thinking about modelling a fresnel lens using CSG, and I have two
> questions.
>
> 1. Is there any reason why a fresnel lens wouldn't actually work in POVRay?
>
> 2. Because of the way they're built, what I need is torii, except instead of
> round, I need them to be diamond-shaped. like, uh, for the second value of
> "round". Is there any way to do this without going beyond the realm of
> primitives? I'm not comfortable enough with light and finishes and whatnot to
> get into making any kind of complex base shapes yet.

You could take a bunch of spheres, chop them into the requisite bits, and then
put them all into a single union. This is the basic idea behind a fresnel lens,
if I read the Wikipedia article correctly. You would basically be simulating (or
re-enacting) the actual construction process behind the earliest lenses.

I don't think you want torii, as the horizontal curvature would be too great.
Well, none of the graphics in the WP article show torical lenses, just cleverly
assmbled spherical sections.

As for the rest, I can't say as I've never tried to simulate optics in POV-Ray.

-Mike


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From: Killroy Quartermaine
Subject: Re: Concerning fresnel lenses
Date: 11 Jul 2008 05:45:00
Message: <web.48772abdd872648f4cdc498c0@news.povray.org>
"SharkD" <nomail@nomail> wrote:
> "Killroy Quartermaine" <iam### [at] yahoocom> snipped most of this post:
> > So I was thinking about modelling a fresnel lens using CSG, and I have two
> > questions.
>
> You could take a bunch of spheres, chop them into the requisite bits, and then
> put them all into a single union. This is the basic idea behind a fresnel lens,
> if I read the Wikipedia article correctly. You would basically be simulating (or
> re-enacting) the actual construction process behind the earliest lenses.

Well, I'll be. Yeah, that's actually a far better way to do this, I think.
Thanks.

>
> As for the rest, I can't say as I've never tried to simulate optics in POV-Ray.
>
> -Mike

well, when I've got it done, I'll let you know how it all works out.


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From: Alain
Subject: Re: Concerning fresnel lenses
Date: 11 Jul 2008 22:42:39
Message: <48781a1f$1@news.povray.org>
Killroy Quartermaine nous illumina en ce 2008-07-11 01:02 -->
> So I was thinking about modelling a fresnel lens using CSG, and I have two
> questions.
> 
> 1. Is there any reason why a fresnel lens wouldn't actually work in POVRay?
None at all. In fact, you are not the first one who want to do that. In fact, it 
have been done already.
> 
> 2. Because of the way they're built, what I need is torii, except instead of
> round, I need them to be diamond-shaped. like, uh, for the second value of
> "round". Is there any way to do this without going beyond the realm of
> primitives? I'm not comfortable enough with light and finishes and whatnot to
> get into making any kind of complex base shapes yet.
> 
> 
Fresnel lences are constructed from rings carved out from a sphere.
You can build one that way, or use a thin cylinder, or a disk, and use normals.
If you look trough, it will act like a real one, and, using photons, it will 
focalise light.

-- 
Alain
-------------------------------------------------
Moonies: Only really happy shit happens.


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