I've only lately become aware that a box can be made with zero thickness (I
picked this up from some Screen.inc code.) It never occurred to me to try it--I
guess because a box can't be *scaled* this way, and the idea seemed
counter-intuitive anyway. But it's very useful for projecting images onto (as an
example), as it's an easy way to get no visible 'edge thickness.'

But if an interior_texture is then applied to the box, it completely
disappears--as seen from the front. (And, BTW, with no 'graininess' that might
be expected from floating-point errors--i.e., no random mixing of the
front-projected image with rgbt 1 on a pixel-by-pixel basis.) I would have
expected to see the transparent pigment only if I rotated the box to look at its
rear surface--like a POV-Ray disc.

So this behavior begs the question (mostly one of sheer curiosity): What is
considered the inside/outside of such a box? My first thought it that there is
*only* an inside now.

Post a reply to this message

On 01/03/2013 05:24 PM, Kenneth wrote:
> I've only lately become aware that a box can be made with zero thickness (I
> picked this up from some Screen.inc code.) It never occurred to me to try it--I
> guess because a box can't be *scaled* this way, and the idea seemed
> counter-intuitive anyway. But it's very useful for projecting images onto (as an
> example), as it's an easy way to get no visible 'edge thickness.'
>
> But if an interior_texture is then applied to the box, it completely
> disappears--as seen from the front. (And, BTW, with no 'graininess' that might
> be expected from floating-point errors--i.e., no random mixing of the
> front-projected image with rgbt 1 on a pixel-by-pixel basis.) I would have
> expected to see the transparent pigment only if I rotated the box to look at its
> rear surface--like a POV-Ray disc.
>
> So this behavior begs the question (mostly one of sheer curiosity): What is
> considered the inside/outside of such a box? My first thought it that there is
> *only* an inside now.
>
>
I wonder if Doctor Who could be in for some similar trouble... ;-)

Expect those who understand how the intersection stack works in such 
cases could figure out exactly what is happening. My first thought was 
perhaps due the points all being coincident, povray might be taking up 
the inside texture first only to find the ray had already exited the box.

Post a reply to this message

William F Pokorny <ano### [at] anonymousorg> wrote:

>
> I wonder if Doctor Who could be in for some similar trouble... ;-)
>

The Tardis is far too complex for mere mortals to understand :-P

> Expect those who understand how the intersection stack works in such
> cases could figure out exactly what is happening. My first thought was
> perhaps due the points all being coincident, povray might be taking up
> the inside texture first only to find the ray had already exited the box.

That sounds better than my thought...I think... :-O

Post a reply to this message