I know someone wrote an extension to allow a plane to transfer rays to 
another plane, so that you can make (for example) two windows side by 
side that overlook different places.  I think it was called "portal 
pigment" but I find no mention of it more recent than 2001.  Help?

I need it to complete a series for 
http://en.wikipedia.org/wiki/Andreini_tessellation -- I made most of the 
images there, with mirrors, and that's not possible for some of the 
lattices on the list.

-- 
Anton Sherwood, http://www.ogre.nu/
"How'd ya like to climb this high *without* no mountain?" --Porky Pine

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Anton Sherwood <bro### [at] poboxcom> wrote:
> I know someone wrote an extension to allow a plane to transfer rays to
> another plane, so that you can make (for example) two windows side by
> side that overlook different places.  I think it was called "portal
> pigment" but I find no mention of it more recent than 2001.  Help?
>

Hi,

I confess to never having heard of something called "portal pigment", and
I'm too lazy to search for it right now ...
..... however, your example of windows showing different places could be made
using MegaPOVs "camera_view" pigment. Essentially you define a camera
looking somewhere into your scene and get a pigment that looks as if you
had rendered that view into an image earlier. As an example they remake the
"desk with a picture on it showing exactly that desk with ..."-scene with
only one render. In that example, all "cameras" are equal, but you could
choose differently, of course.

> I need it to complete a series for
> http://en.wikipedia.org/wiki/Andreini_tessellation -- I made most of the
> images there, with mirrors, and that's not possible for some of the
> lattices on the list.
>

Nice images ! I just love everything that has even remotely to do with
polyhedra ... though I fail to see why you would need mirrors or
"camera_view" for those.

Greetings

Karl

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> Anton Sherwood wrote:
>> I need it [portal pigment or "camera_view"] to complete a series
>> for http://en.wikipedia.org/wiki/Andreini_tessellation -- I made
>> most of the images there, with mirrors, and that's not possible
>> for some of the lattices on the list.

Karl Anders wrote:
> Nice images ! I just love everything that has even remotely to do
> with polyhedra ... though I fail to see why you would need mirrors
> or "camera_view" for those.

By definition these lattices are infinitely deep, and I prefer to 
"cheat" on that fact as little as possible.

Each of those scenes consists of four mirrors (forming 1/48 or 1/24 of 
the basic cube) and four or fewer cylinders.  The appearance of depth 
comes from the decay caused by repeated reflections in imperfect mirrors 
("finish {reflection 0.98}").

I'm more confident in my ability to do it that way than by building a 
finite number of copies of the basic cell; and I'm a big fan of concise 
code!

If anyone's interested in the technicalities --
The mirrors are the boundaries of the space 0 <= x <= y <= z <= 1,
except that in the "alternated" forms the mirror at x=0 is replaced by 
one at x+y=0.  The mirrors form an irregular tetrahedron, and a vertex 
of the lattice is placed somewhere within it (or on its boundaries).  A 
lattice-edge (cylinder) goes from the vertex to its image in each of the 
mirrors, and the vertex is so placed that each nontrivial edge has the 
same length.

-- 
Anton Sherwood, http://www.ogre.nu/
"How'd ya like to climb this high *without* no mountain?" --Porky Pine

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Karl Anders wrote:
> ..... however, your example of windows showing different places could
> be made using MegaPOVs "camera_view" pigment. Essentially you define
> a camera looking somewhere into your scene and get a pigment that
> looks as if you had rendered that view into an image earlier. As an
> example they remake the "desk with a picture on it showing exactly
> that desk with ..."-scene with only one render. . . .

Thanks but it's not quite what I need.  The "view" in my lattice
depends on the angle at which the ray meets the "pigment".

-- 
Anton Sherwood, http://www.ogre.nu/
"How'd ya like to climb this high *without* no mountain?" --Porky Pine

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Anton Sherwood wrote:
> I know someone wrote an extension to allow a plane to transfer rays to 
> another plane, so that you can make (for example) two windows side by 
> side that overlook different places.  I think it was called "portal 
> pigment" but I find no mention of it more recent than 2001.  Help?
> 

You mean this probably:
 >http://news.povray.org/povray.binaries.images/thread/%3Cchrishuff-484A65.16045221012001%40news.povray.org%3E/?mtop=21

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