POV-Ray : Newsgroups : povray.bugreports : sphere slicing problem : Re: sphere slicing problem Server Time
1 Dec 2021 16:49:06 EST (-0500)
  Re: sphere slicing problem  
From: jr
Date: 18 Oct 2019 16:00:01
Message: <web.5daa18f6401c5809feeb22ff0@news.povray.org>
hi,

Le_Forgeron <jgr### [at] freefr> wrote:
> Le 14/10/2019 à 19:20, Bald Eagle a écrit :
> > "jr" <cre### [at] gmailcom> wrote:
> >> does not for me.  :-(  I get solid (filled) circles, not rings.
> > Ah.
> >> that may not always be an option.  the idea is to slice arbitrary objects
> >> (suitably scaled + positioned).  the object may not always be my own work
> >> though.
> > Sounds like that ex-post facto texturing lots of people would like...
>
> what about then, using cutaway_texture ?

hey, thanks.  like Bald Eagle, I had not seen this "object modifier" before.
alas, adding it seems to make no discernable difference to what I now get.  in
accordance withe the reference, I changed the "slice" to:
box {p1, p2 hollow no_reflection no_shadow
  texture {pigment {srgbt 1}}
  interior_texture {pigment {srgbt 1}}
}

and use it in:
intersection {
  object {O}
  object {S}
  cutaway_texture
  double_illuminate
}

with "tight" antialias settings in the .ini this gives reasonably good results.

however, _the_ problem is the "pathological" case of parallel-to-camera, as Bill
P identified when he asked "what happens with a box".  I'm currently wondering
whether using a perspective camera for "difficult" shapes mightn't be better.
and for shapes like spheres + tori I may get milage our of lowering the vertical
resolution (ie thicker slices).

> I have a feeling it was made for these people.

and in reply to Bald Eagle:

the Lohmueller tip is confusing.  haven't tried yet but the documentation is
quite clear that the direction vector is not used with prthographic cameras.
have you come across working code which utilises the "trick"?


regards, jr.


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