

Am 15.12.22 um 19:36 schrieb Bald Eagle:
> Lars Rohwedder <rok### [at] gmxde> wrote:
>> I'd expected that the areas "far outside" of the Mandelbrot set (outside
>> of the red cylinder) would have "low" values, so they are far "outside"
>> of the isosurface. But they aren't, so the result is that the whole
>> contained_by box is filled.
>>
>> Is it a bug how mandel pattern & isosurface work together or is the bug
>> in my scene file? :/
>>
>> Lars R.
>
> It looks like the pattern drops off to zero.
Correct.
According to the documentation of isosurface, all points with function
value < threshold are "inside" the isosurface object.
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".
So I had expected that a formula like 0.9  mandel would give the
desired result:
* the points inside the Mandelbrot set will be <0, so are consideded
as "inside" the rendered shape.
* the points far away of the Mandelbrot set will be >0, so are
"outside" of the rendered shape.
But the rendering looks completely different than expected, see attached
mandel0.9.png
Changing the formula to 0.5mandel2(x,y,z) it looks much more than a
Mandelbrot set, but it is "inverse": the Mandelbrot set is "outside",
the surrounding areay is inside. Hence I switched the sign, so the
forumla becomes mandel(x,y,z)0.5.
So the inside of the Mandelbrot set becomes the inside of the
isosurface, as expected, but also the far away areas are "inside", which
is _not_ what I expected.
What went wrong here?
Lars R.
pS: The "open" keyword just removes the visibility of the contained_by
object, but I consider it helpful to see what is insided and what it is
outside of the isosurface object.
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Attachments:
Download 'mandel0.5.png' (25 KB)
Download 'mandel0.9.png' (20 KB)
Preview of image 'mandel0.5.png'
Preview of image 'mandel0.9.png'

