POV-Ray : Newsgroups : povray.general : Trying to create a particular object Server Time: 23 Oct 2019 03:17:10 GMT
  Trying to create a particular object (Message 1 to 6 of 6)  
From: David Kraics
Subject: Trying to create a particular object
Date: 26 Sep 2019 01:10:01
Message: <web.5d8c0f91b070c22db80758900@news.povray.org>
Hi there. Over the many years of playing with POVray, I have often tried to
recreate things that require a certain object. I want to go from a cylinder to a
cone, but I want it to be tapered in, rather than a straight cut into the angle
of the cone. Sort of like going from cylinder to half-sphere to cone. Does this
make sense? Maybe this helps to picture what I had in mind. Right now I want to
recreate a Navy submarine. The shape of the sub transits smoothly from a
cylinder to ending in a cone shape in the rear, without a sharp change in angle.
Anyone have any suggestions?


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From: Bald Eagle
Subject: Re: Trying to create a particular object
Date: 26 Sep 2019 10:30:00
Message: <web.5d8c925d97ff03a54eec112d0@news.povray.org>
"David Kraics" <bar### [at] aolcom> wrote:
> Hi there. Over the many years of playing with POVray, I have often tried to
> recreate things that require a certain object. I want to go from a cylinder to a
> cone, but I want it to be tapered in, rather than a straight cut into the angle
> of the cone. Sort of like going from cylinder to half-sphere to cone. Does this
> make sense?

Convex, concave, or sigmoid (both - one, then the other)?

> Maybe this helps to picture what I had in mind. Right now I want to
> recreate a Navy submarine. The shape of the sub transits smoothly from a
> cylinder to ending in a cone shape in the rear, without a sharp change in angle.
> Anyone have any suggestions?

Spindle of a spindle torus, difference a "horn" torus away from a cylinder
https://en.wikipedia.org/wiki/Torus

non-linearly scaled sphere,

http://www.econym.demon.co.uk/isotut/substitute.htm

the lemon

http://wiki.povray.org/content/Reference:Lemon

isosurface,

Do any of these shapes look interesting?
http://www.econym.demon.co.uk/isotut/builtin2.htm  (and subsequent pages)

use intersecting spheres around an axis to make a sort of 3D lemniscate (if
that's not redundant with any of the above...


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From: Thomas de Groot
Subject: Re: Trying to create a particular object
Date: 26 Sep 2019 10:59:54
Message: <5d8c9a2a$1@news.povray.org>
Op 26/09/2019 om 12:26 schreef Bald Eagle:
> 
> "David Kraics" <bar### [at] aolcom> wrote:
>> Hi there. Over the many years of playing with POVray, I have often tried to
>> recreate things that require a certain object. I want to go from a cylinder to a
>> cone, but I want it to be tapered in, rather than a straight cut into the angle
>> of the cone. Sort of like going from cylinder to half-sphere to cone. Does this
>> make sense?
> 
> Convex, concave, or sigmoid (both - one, then the other)?
> 
>> Maybe this helps to picture what I had in mind. Right now I want to
>> recreate a Navy submarine. The shape of the sub transits smoothly from a
>> cylinder to ending in a cone shape in the rear, without a sharp change in angle.
>> Anyone have any suggestions?
> 
> Spindle of a spindle torus, difference a "horn" torus away from a cylinder
> https://en.wikipedia.org/wiki/Torus
> 
> non-linearly scaled sphere,
> 
> http://www.econym.demon.co.uk/isotut/substitute.htm
> 
> the lemon
> 
> http://wiki.povray.org/content/Reference:Lemon
> 
> isosurface,
> 
> Do any of these shapes look interesting?
> http://www.econym.demon.co.uk/isotut/builtin2.htm  (and subsequent pages)
> 
> use intersecting spheres around an axis to make a sort of 3D lemniscate (if
> that's not redundant with any of the above...
> 
> 

I would add to that the 'ovus' object from the basic round objects 
library in POV-Ray.

[aside]
This is typically a case where the Moray program would come in handy...
[/aside]

-- 
Thomas


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From: Bill Pragnell
Subject: Re: Trying to create a particular object
Date: 26 Sep 2019 12:35:00
Message: <web.5d8caff297ff03a51b6c6b3a0@news.povray.org>
"David Kraics" <bar### [at] aolcom> wrote:
> I want to go from a cylinder to a
> cone, but I want it to be tapered in, rather than a straight cut into the angle
> of the cone.

In addition to the other suggestions, you could use a lathe object:

http://www.povray.org/documentation/3.7.0/r3_4.html#r3_4_5_1_8

which takes a 2D curve and rotates it around an axis. If you don't fancy
creating the curves by hand, you could use Inkscape (https://inkscape.org/)
which can export curves as POV-Ray splines. These can then be pasted into your
scene files.

Bill


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From: Bald Eagle
Subject: Re: Trying to create a particular object
Date: 26 Sep 2019 17:40:06
Message: <web.5d8cf74097ff03a54eec112d0@news.povray.org>
"Bill Pragnell" <bil### [at] hotmailcom> wrote:

> In addition to the other suggestions, you could use a lathe object:

Ah, yes, and the SOR object as well.

Plus there's EP-Spline
https://agalena.nfshost.com/b1/software/epspline-prism-and-lathe-editor/


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From: Alain Martel
Subject: Re: Trying to create a particular object
Date: 27 Sep 2019 16:03:56
Message: <5d8e32ec$1@news.povray.org>
Le 2019-09-25 à 21:08, David Kraics a écrit :
> Hi there. Over the many years of playing with POVray, I have often tried to
> recreate things that require a certain object. I want to go from a cylinder to a
> cone, but I want it to be tapered in, rather than a straight cut into the angle
> of the cone. Sort of like going from cylinder to half-sphere to cone. Does this
> make sense? Maybe this helps to picture what I had in mind. Right now I want to
> recreate a Navy submarine. The shape of the sub transits smoothly from a
> cylinder to ending in a cone shape in the rear, without a sharp change in angle.
> Anyone have any suggestions?
> 
> 

What about a sphere_sweep ?
In some cases, using blobs can be the way to go.

If all else fails, there are bicubic patches and meshes that can be used.


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