This is just a test scene for the portal pigment. The transparent blue 
thing on the left is an aid for moving the "other" end of the portal 
around.
The way things work currently is:
Step 1: Move the portal object to wherever you want the portal to view 
from.
Step 2: Apply the portal pigment.
Step 3: Move the portal object to wherever you want the actual portal to 
be.

Whenever a ray hits the portal object (which is in the position defined 
by step 3), it stops and reappears on the same position relative to the 
object, in the position it was in before step 2. The result: it appears 
that light goes into a hole in space, disappears, and reappears from 
somewhere else. It isn't two-way though, you would need two portals for 
that. I plan to add a way to transform the "other end" from the pigment 
itself so you don't have to mess around with moving the object to the 
exit point before adding the portal pigment. And though it may seem odd 
at first, it was the only useable method I could come up with...and it 
is actually very useable, though I made a simple macro to transform it 
to each position.

Anyway, this is the type 0 portal...the rays exit it going in the same 
direction relative to each other that they went in, though the direction 
of all of them can change, when the "other end" is rotated for example. 
If you move around the "viewing end", you can see into the portal at 
different angles.
Other types are type 1, where you specify a direction for the rays (kind 
of like an orthographic camera), type 2, where the direction of the rays 
is defined by the normal of the portal object, and type 3, the "security 
camera" type, which is used like an image_map but takes a camera as the 
source (and which isn't working yet).
The number of portals you see through is affected by max_trace_level, 
and you can have a portal that looks into itself, giving the "hall of 
mirrors" effect (you can see a little of that in this image). The 
rendering speed is about the same as ordinary transparence or 
reflection. Oh, and shadows don't work correctly yet...and I'm not 
really sure what "correct" is in this case. The portals are currently 
opaque as far as shadows are concerned.

There will be two kinds of transparency...one affecting things seen on 
the other end of the portal, and one affecting things seen through the 
portal object, so you can have a kind of "hologram" effect.
I have posted an animation to my web site:
http://homepage.mac.com/chrishuff/pov/portal_pigment.mov
It is a QuickTime Movie...I don't have any good way to generate MPEGs. 
(the one MPEG utility I have resulted in jerky, significantly lower 
quality results and a larger file size)

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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