POV-Ray : Newsgroups : povray.bugreports : sphere slicing problem : Re: sphere slicing problem Server Time
1 Dec 2021 17:00:51 EST (-0500)
  Re: sphere slicing problem  
From: jr
Date: 18 Oct 2019 18:30:01
Message: <web.5daa3c4b401c5809feeb22ff0@news.povray.org>
hi,

"Bald Eagle" <cre### [at] netscapenet> wrote:
> "jr" <cre### [at] gmailcom> wrote:
> adding it seems to make no discernable difference to what I now get.
>
> I don't think he was suggesting it would - he was just commenting on my "ex post
> facto" differencing comment.  That's a whole different story.

</blush>  misread.  apologies.

> > 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).
>
> This almost makes me wonder if you can do some sort of weird wide-angle /
> panoramic render and then re-map it with --- for lack of a better understanding
> and proper vocabulary - an anamorphic camera

I can see what you mean but that's way beyond my .. pay grade.

ideally there'd be a simple way of, say, using a (slightly) offset perspective
camera, and relating that angle to some compensating factor to approximate the
orthographic equivalent (a bit like an effect using a matrix to slant/skew an
object, then reversing that).

> > 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"?
> I believe you can just make a simple animation of a camera getting closer and
> closer to a shape with a gradient pigment along the object-camera axis.  Maybe
> slightly off-axis, so that you can see the effect better.
> The camera will start to exclude all of the parts of the object "behind" it, and
> you'll effectively get a slicing effect.
> I've done this plenty of times by accident when setting up scenes with the
> orthographic camera.

:-)  yes, I too have found myself .. inside, unexpectedly.  anyway, the
"remainder" would still need to be cut/sliced, so it looks like using a box to
intersect seems unavoidable.


regards, jr.


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