POV-Ray : Newsgroups : povray.beta-test : SUGGESTION: Hollow 0.05 Server Time
7 Dec 2021 12:48:54 EST (-0500)
  SUGGESTION: Hollow 0.05 (Message 11 to 20 of 21)  
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From: Sven Littkowski
Subject: Re: SUGGESTION: Hollow 0.05
Date: 1 Dec 2017 16:56:30
Message: <5a21d00e$1@news.povray.org>
On 01.12.2017 14:56, clipka wrote:
> ... and the reason you're having trouble with this use case is pretty
> much the same reason why that suggested feature would be darn difficult
> to implement as well.


Yes, I understood that already. :-)

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From: Le Forgeron
Subject: Re: SUGGESTION: Hollow 0.05
Date: 2 Dec 2017 04:18:02
Message: <5a226fca$1@news.povray.org>
Le 01/12/2017 à 13:46, Bald Eagle a écrit :
> clipka <ano### [at] anonymousorg> wrote:
> 
>>> This would make the sphere hollow but keeps an inner wall thickness of
>>> 0.05 units.
>>
>> That's technically impossible.
>>
>> (Well, strictly speaking something along the lines may be possible for
>> spheres, but it can't be generalized to arbitrary primitives.)
> 
> Well, technically it's possible, and practically it's done.
> This is a type of thing called an "offset curve" - such as what Dave Blandston
> does with his fancy text.  This is a feature available in graphics programs,
> probably Mathematica, CAD software, and Silhouette / Cricut type design
> programs.
> 
> The problem of course is writing a robust algorithm that does what you expect it
> to do given some general, unknown input.
> Doing this with a convex hull of points like "O" is fairly easy, the real
> problems of course come with concave shapes like "C" where things start to
> collide --- and then what?
> 
> It would be a NICE feature - but it's anything but trivial to code, which is why
> it's usually only seen in commercial software packages, and you almost always
> have to pay extra for a "pro" or "plus" version to have that functionality.
> 
> 
I second CLipka: it's technically impossible.

You can do it when all you have is mesh of triangles, but that's not
what POV-Ray is made of.

And if you want to manipulate meshes, you'd better do it in one of the
nice visual editors that exist. (I'm familiar with meshlab, but that's
not the only one)


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From: Stephen
Subject: Re: SUGGESTION: Hollow 0.05
Date: 2 Dec 2017 04:57:20
Message: <5a227900$1@news.povray.org>
On 02/12/2017 09:18, Le_Forgeron wrote:
> And if you want to manipulate meshes, you'd better do it in one of the
> nice visual editors that exist. (I'm familiar with meshlab, but that's
> not the only one)

Blender has a modifier called "Solidify" which does that very thing.

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Regards
     Stephen


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From: Alain
Subject: Re: SUGGESTION: Hollow 0.05
Date: 2 Dec 2017 13:57:57
Message: <5a22f7b5@news.povray.org>
Le 17-12-02 à 04:57, Stephen a écrit :
> On 02/12/2017 09:18, Le_Forgeron wrote:
>> And if you want to manipulate meshes, you'd better do it in one of the
>> nice visual editors that exist. (I'm familiar with meshlab, but that's
>> not the only one)
> 
> Blender has a modifier called "Solidify" which does that very thing.
> 

Yes, and it only work when you are using meshes.


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From: Stephen
Subject: Re: SUGGESTION: Hollow 0.05
Date: 2 Dec 2017 14:44:41
Message: <5a2302a9$1@news.povray.org>
On 02/12/2017 18:58, Alain wrote:
> Le 17-12-02 à 04:57, Stephen a écrit :
>> On 02/12/2017 09:18, Le_Forgeron wrote:
>>> And if you want to manipulate meshes, you'd better do it in one of the
>>> nice visual editors that exist. (I'm familiar with meshlab, but that's
>>> not the only one)
>>
>> Blender has a modifier called "Solidify" which does that very thing.
>>
> 
> Yes, and it only work when you are using meshes.

Isn't that what you were talking about in what I quoted?

-- 

Regards
     Stephen


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From: Cousin Ricky
Subject: Re: SUGGESTION: Hollow 0.05
Date: 2 Dec 2017 15:09:19
Message: <5a23086f$1@news.povray.org>
On 12/01/2017 07:03 AM, Sven Littkowski wrote:
> the "hollow" keyword makes a shape hollow. My suggestion is, to make it
> possible to add behind this keyword a small number that specifies a
> "wall thickness".

No, no, no, no, NO!

This is not the purpose of the 'hollow' keyword, as you have indicated 
that you understand, elsewhere in this thread.  In addition to the 
prohibitive difficulty in implementing such a feature, it would just add 
to the confusion over the purpose of 'hollow', a confusion that is 
acknowledged even in the documentation (Questions and Tips, formerly in 
the tutorial, but now in the online knowledge base).


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From: Sven Littkowski
Subject: Re: SUGGESTION: Hollow 0.05
Date: 2 Dec 2017 16:35:54
Message: <5a231cba$1@news.povray.org>
Happy to see, that we get now, despite the technical hurdles, an
interesting discussion coming up. I will follow. :-)

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From: Sven Littkowski
Subject: Re: SUGGESTION: Hollow 0.05
Date: 2 Dec 2017 16:36:41
Message: <5a231ce9$1@news.povray.org>
On 02.12.2017 15:10, Cousin Ricky wrote:
> No, no, no, no, NO!

Noted. :-)

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From: mr 3d
Subject: Re: SUGGESTION: Hollow 0.05
Date: 2 Jan 2018 15:30:01
Message: <web.5a4beb59627182d033437890@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> clipka <ano### [at] anonymousorg> wrote:
>
> > ... and the reason you're having trouble with this use case is pretty
> > much the same reason why that suggested feature would be darn difficult
> > to implement as well.
>
> Right.
> A first step towards a solution would essentially accomplish an efficient
> meshification of the object - which may be what Sven might want to play with.
>
> Then you'd translate the points along the normal vector to expand/shrink the
> object as a 3D offset-curve.
>
> NOT trivial.

Hi, this is my first post to this group. You did wonderful job ;)

To the point. Yes, I've attempted to do that, called it "thick wall style". It
was part of a project of visualization of uncertainty, namely structure of
cardiac veins (yes, POVRay may be used as a scientific tool ;) or just interval
data.

It is really hard to do that without artifacts.

Ref:
http://ieeexplore.ieee.org/document/7973435/ DOI:10.23919/MIPRO.2017.7973435


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From: MessyBlob
Subject: Re: SUGGESTION: Hollow 0.05
Date: 29 Nov 2018 14:00:01
Message: <web.5c0035c1627182d0d691ab270@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> clipka <ano### [at] anonymousorg> wrote:
>
> > ... and the reason you're having trouble with this use case is pretty
> > much the same reason why that suggested feature would be darn difficult
> > to implement as well.
>
> Right.
> A first step towards a solution would essentially accomplish an efficient
> meshification of the object - which may be what Sven might want to play with.
>
> Then you'd translate the points along the normal vector to expand/shrink the
> object as a 3D offset-curve.
>
> NOT trivial.

If you can make an isosurface out of it, then it's possible to make an 'offset
surface' general solution, which can be combined with CSG to create the skin.
Caveat: it might be slow to render, especially if you're using several 'power'
functions for smooth transitions.


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