POV-Ray : Newsgroups : povray.advanced-users : Making Patterns with functions : Re: Making Patterns with functions Server Time
23 Feb 2024 11:18:32 EST (-0500)
  Re: Making Patterns with functions  
From: Kenneth
Date: 24 Jan 2024 02:00:01
Message: <web.65b0b43dd81b84799b4924336e066e29@news.povray.org>
"Kenneth" <kdw### [at] gmailcom> wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote:

>
> > Use Mike Williams' "shell" trick for isosurfaces to give an infinitely
> > thin line a visible thickness
>
>
> Do you have a link to this trick, or a short explanation? (--keeping my fingers
> crossed--)

I just took a look at the Mike Williams 'isosurface tutorial' that you packaged
and sent to me as a .pdf file some years ago. Is the technique you refer to here
the same as Mike's 'thickening' trick using 2 parallel surfaces (page 18 of
149)? Or is it something different?

Thickening--
If we have a function F(x,y,z) we can turn it into two parallel surfaces by
using abs(F(x,y,z))-C where C is some small value. The original function should
be one that works with zero threshold. The two resulting surfaces are what you
would get by rendering the original function with threshold +C and -C, but
combined into a single image. The space between the two surfaces becomes the
"inside" of the object. In this way we can construct things like glasses and
cups that have walls of non-zero thickness.

[example:]
#declare F = function {y + f_noise3d (x*2, 0, z*2)}
isosurface {
function {abs (F(x, y, z))-0.1}
......


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