POV-Ray : Newsgroups : povray.general : Media Alignment ? : Re: Media Alignment ? Server Time
12 Aug 2024 19:37:17 EDT (-0400)
  Re: Media Alignment ?  
From: Spider
Date: 18 Jan 1999 16:07:57
Message: <36A3A1B3.69FDDF02@bahnhof.se>
I thought I read somewhere in the doc's that it is calculated if inside a hollow
object,
otherways not, (calculating in and outside)

//Spider

Ron Parker wrote:
> 
> On Mon, 18 Jan 1999 02:37:53 -0800, Ken <tyl### [at] pacbellnet> wrote:
> >Ken wrote:
> >
> >> On a recent scene I was working on ( see povray images "If you can't go
> >> to heaven") I was using media inside of a plane. I could only see the media
> >> when the camera is inside the plane and not while outside. Why ?
> >> The plane used is at y*0 with the camera at y*-2 using planar for the
> >> density type. If I put the camera at y*2 or even y*20 with the look_at
> >> at y*-10 to make sure I'm pointed an the surface of the plane the media is
> >> still invisible in the scene.
> >>
> >> --
> >> Ken Tyler
> >>
> >> tyl### [at] pacbellnet
> >
> >Perhaps Ken it is because a plane is not a closed container ?
> 
> That's about right.  For fun, try putting another object inside the
> plane. Then you'll be able to see media from outside the plane, but only
> in the places where the ray ends up hitting the other object (even if
> the object itself is completely invisible.)
> 
> POV only calculates media effects along a ray after it determines the
> exit point for the ray.  Planes, being infinite, tend not to have exit
> points unless the ray enters another object or starts from inside the
> plane.  (And not all rays that start inside the plane have exit points:
> try pointing your camera parallel to the plane when it's inside for
> another weird effect) To fix this, you might try adding another plane
> with the same normal but situated below the plane you're working with,
> or you might try using a large box.


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