You pick up and read article <di2moi$37r$1@chho.imagico.de>, written by 
Christoph Hormann  <chr### [at] gmxde>. It says:
>I see your point but this is not as simple as it sounds.

I didn't think it would be that simple, as you can see by the original posting
(the one I rashly canceled). Actually the version I posted on
povray.programming is slightly better developed.

>Raytracing more or less relies on the rules of euclidian geometry (see 
>http://en.wikipedia.org/wiki/Euclidian), esp. for shadows and by 
>breaking this you won't get consistent result any more.

You have a point here. Shadow casting works simply by shooting a ray from a
surface point to a light source (depends on the first axiom), but it may be
difficult to find a light source through a portal. There may be a not-too-bad
solution for a surface like a polygon or a cube, but most curved surfaces would
present difficulty. Of course, differently-shaped surfaces make mapping from
one to the other difficult for any kind of tracing (just how do you map a cube
onto a torus, for instance?), so it might be necessary to restrict the object
type severely, which calls into question teleportation's relation to textures
(finish *or* pigment).

OTOH, perhaps photon mapping won't have the same problem as shadow casting, as
long as portals are two-way. But that probably has nothing to do with the
shadow problem.

I'm definitely getting the feeling that some technique would have to be
developed just to handle shadows for this feature (if it's even slightly
feasible). This will take a lot of thought.

-- 
| Email: Daniel Dawson <ddawson at icehouse.net>      ifMUD: DanDawson |
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