POV-Ray : Newsgroups : povray.binaries.images : request for special lens-like shape Server Time
16 Aug 2024 10:26:31 EDT (-0400)
  request for special lens-like shape (Message 1 to 6 of 6)  
From: Rune
Subject: request for special lens-like shape
Date: 3 Mar 2002 07:26:23
Message: <3c82166f@news.povray.org>
See povray.advacned-users

Rune
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From: Tim Nikias
Subject: Re: request for special lens-like shape
Date: 3 Mar 2002 09:22:22
Message: <3C8231B4.CCB9DA30@gmx.de>
Why don't you use a CSG-merged torus with cylinder?
Scaling the torus could smoothen the curvature near the
flat area... Ah, but then the curvature at the rim would increase...

Try using a lathe with some splines. I'd think you'd have enough
freedom to create the shape you are looking for, and calculating
the splines for spheres isn't very difficult.


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Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html


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From: Rune
Subject: Re: request for special lens-like shape
Date: 3 Mar 2002 11:29:02
Message: <3c824f4e$1@news.povray.org>
"Tim Nikias" wrote:
> Why don't you use a CSG-merged torus with cylinder?
> Scaling the torus could smoothen the curvature near
> the flat area...

Scaling the torus will make the curvature slightly smaller, but there will
still be an abrupt change. You can tell that there's an abrupt change if you
make the object reflective and you then clearly can see where the curved
part starts and you always can see that when using a union of a torus and a
cylinder...

A lathe is an interesting suggestion, but unfortunately lathes have the
problem that cubic splines can't really go smoothly from a curve to a
completely straight line without curving the opposite way first. It's almost
impossible. :(

Anyway, I found an isosurface function that works fine. I just wish it
rendered faster. I posted it to povray.advanced-users. Maybe it can be
optimized?

Rune
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3D images and anims, include files, tutorials and more:
Rune's World:    http://rsj.mobilixnet.dk (updated Feb 16)
POV-Ray Users:   http://rsj.mobilixnet.dk/povrayusers/
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From: Tim Nikias
Subject: Re: request for special lens-like shape
Date: 3 Mar 2002 12:19:06
Message: <3C825B1F.47C5E1EB@gmx.de>
>
> A lathe is an interesting suggestion, but unfortunately lathes have the
> problem that cubic splines can't really go smoothly from a curve to a
> completely straight line without curving the opposite way first. It's almost
> impossible. :(
>

If you just use two or three exact same nodes after each other
(like [...]<0,3,0>,<0,3,0>,<0,3,0>,[...]) at the place the
straight shall start, and again some points where it ends,
you'll get a flat area without an abrupt change. I'm not sure
however how many (two at least) nodes you'll need for that. But
that should make lathe possible.

Concerning the iso, I'm haven't really looked at them yet, and
thus can give you no aid... :-(


--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html


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From:
Subject: Re: request for special lens-like shape
Date: 3 Mar 2002 17:27:51
Message: <3c82a367@news.povray.org>
> Anyway, I found an isosurface function that works fine. I just wish it
> rendered faster. I posted it to povray.advanced-users. Maybe it can be
> optimized?

what about a mesh?
(just in case that the thing has to *look* as it would have a smooth
surface)
regards
SY


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From: AC
Subject: Re: request for special lens-like shape
Date: 3 Mar 2002 17:41:55
Message: <3c82a6b3@news.povray.org>
"Tim Nikias" <tim### [at] gmxde> wrote in message
news:3C8231B4.CCB9DA30@gmx.de...
> Why don't you use a CSG-merged torus with cylinder?

How about a CSG merge  "Sphere-Cylinder-Sphere"

Ambis


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