[pstricks] overlays or similar methods

[Christoph Bersch]

Hi!

As far as I know there is no real possiblity of making overlays with
PSTricks. So maybe some of you has an alternativ idea to solve my problem:

For the moment in my package pst-optexp it's only possible to draw
single beams:

           | (beam)
           |
           | /
     -------/
           / (mirror)
          /

and I have to draw the beams before the components in order to have the
beam placed behind the component lines. So far there is no problem.

But I'm thinking about allowing the use of larger beams:

         | | (beams)
         | |
         | | /
    --------/
         | /
    ------/ (mirror)
         /

Now I could define a parameter 'beamwidth' and create two additional
\pnode within the component that can be used after the component was set
to draw the two beams.
But by this the nodes would be accessible only _after_ the component was
drawn and thus for the moment I see no possibility to draw the beams
_behind_ the components.

Is it in some way possible to accomplish this?

1. define new nodes in the component
2. later draw a line using this nodes but to draw this lines behind
   the lines of the component

Hopefully the problem is clear

Thanks for help
Christoph