POV-Ray : Newsgroups : povray.general : min_ and max_extent of an intersection object : Re: min_ and max_extent of an intersection object Server Time
15 Jul 2024 13:35:47 EDT (-0400)
  Re: min_ and max_extent of an intersection object  
From: Thomas de Groot
Date: 27 Jun 2020 02:44:06
Message: <5ef6eab6$1@news.povray.org>
Op 26/06/2020 om 12:51 schreef Bald Eagle:
> 
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> I should have known of course, and instead of swearing by Eagle the
>> Bald, sacrificing nameless things to the Clipka idol and invoking the
>> good spirit of Saint William of the Pokorny (in that order) for a couple
>> of days, I should have opened the Grimoire and read:
> 
> ..oO(Oh boy, he's swearing again...)

Couldn't be helped ;-)

> 
>> "Note: This is not perfect, in some cases (such as CSG intersections and
>> differences or isosurfaces) the bounding box does not represent the
>> actual dimensions of the object."
>>
>> The hell it doesn't!
> 
> Well, yes, we all knew that - which is what jr's bounding macro - using trace ()
> - is all about, and my attempt at doing the same using SVD were all about.
> I had a bit of a hard time visualizing some of what the docs were saying a while
> back, and clipka gave a little more explanation about about certain pathological
> cases. (presumably he was not referring to you at the time)
> 

Unfortunately, his bounding macro does not work correctly either in this 
case (see my answer to jr).

> If your human/mathematical knowledge lets you know approximately the range of a
> function in an isosurface, but you don't know _exactly_the bounds of the
> surface, you can iterate through the function with a nested x, y, z #for loop
> and use min and max to update the value of an indicator with each evaluation.
> 
> 

Well, I was not working with isosurfaces in this particular case but 
with good old CSG's. However, I shall keep this suggestion in mind (if 
my dreadful memory permits; I totally forgot about jr's macro...).

-- 
Thomas


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