"blooflame" <nomail@nomail> wrote:

> How would I do this? My (naive?) thought process is to define each sheet as
> a "box" with dimensions proportional to how a sheet of glass is (thin
> front-to-back, rectangular), then create images in the plane of one side of
> the box. Boxes to be placed in space such that each one is exactly next to
> the other.

That seems the simplest & most logical approach, but if you do that you're
going to get 3 problems:

1. Coincident surfaces - if you stack one box *exactly* next to the other
then Povray won't know which surface to render.  Sometimes it will render
'Box A' and sometimes it will render 'Box B'.  This isn't a problem if the
textures on 'Box A' & 'Box B' are exactly the same, but if they are
different you will get random per-pixel speckling where the surfaces
overlap.  Simple solution is to leave a very small gap between the two
objects.

2. max_trace_level - if this is set too low (the default is 5) then most of
your glass sheets will end up black.  Read the docs to find out why...

3. "My image_map appears on both sides of the box" - as Jim wrote, the
image_map extends infinitely along the Z axis (with planar mapping anyway).
 This means it will appear on both the front & the back of your glass sheet,
which I'm guessing isn't what you want...

After experimenting with a few alternatives, the simplest solution to this
is to create a plain glass sheet, and put the image on a seperate
2-dimensional object placed very slightly in front of the glass sheet
(coincident surfaces again).  The simplest way to make a 2-dimensional
square is with a polygon.

Do not regard this as the ONLY way to solve the problem.  This is Povray and
there are many more ways to skin a cat (or render a skinned one).  Read the
documentation, use the newsgroups & experiment with different techniques.

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