POV-Ray : Newsgroups : povray.beta-test : SUGGESTION: Hollow 0.05 : Re: SUGGESTION: Hollow 0.05 Server Time
1 Dec 2021 04:11:37 EST (-0500)
  Re: SUGGESTION: Hollow 0.05  
From: clipka
Date: 1 Dec 2017 08:01:04
Message: <5a215290$1@news.povray.org>
Am 01.12.2017 um 13:46 schrieb Bald Eagle:
> 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.

As I wrote: It can't be generalized. You'd need to implement such a
feature for each and every primitive type separately.

Also, in some cases you'd need to use more complex math than normally
required by the underlying primitives. For instance, the offset curve to
a 3rd order polynomial spline (such as a bezier spline) can't be
represented as a 3rd order polynomial spline itself (except in special
cases).


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