POV-Ray : Newsgroups : povray.bugreports : "mandel" as function in isosurface has unexpected results : Re: "mandel" as function in isosurface has unexpected results Server Time
2 Jun 2023 08:39:14 EDT (-0400)
  Re: "mandel" as function in isosurface has unexpected results  
From: Bald Eagle
Date: 15 Dec 2022 20:35:00
Message: <web.639bca58c22c158f1f9dae3025979125@news.povray.org>
Lars Rohwedder <rok### [at] gmxde> wrote:

> According to the documentation of isosurface, all points with function
> value  < threshold are "inside" the isosurface object.

Wellll...... it's an isoSURFACE, so there really is no inside, unless (IIRC) for
csg you use all_intesections

> The "mandel" pattern is "low" (near zero) far away from the Mandelbrot
> set, increases slowly near the border of the set and is 1 inside the
> "apple shape" set itself (with default values for "interior" and "exterior".

Can you cite that with a link, or is that your working hypothesis?

> So I had expected that a formula like 0.9 - mandel would give the

> What went wrong here?

Part of what's going wrong is that mandel is a POV-Ray pattern that has a built
in color map.   And that wreaks hell with everything right from the beginning.

I'd say try using:

#declare Mandel = function { pigment {mandel 1000 exterior 1, 1 color_map {[0
rgb 0] [1 rgb 1]}}}

But you're having more success than I am.

Maybe you post your full scene as an attachment, and someone can figure this
out.   All I'm getting right now is a hard-to-visualize infinitely thin layer.

You can try z-mandel.red or mandel (x, y, 0), or any of the other usual tricks.

- BW

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