[GEM-dev] some new code

[Tom Schouten]

> In the discussions so far, the idea put forth is to have pbuffers as 
> user configurable render targets just like a display window.  I don't 
> know if any of the code to do this exists anywhere yet, but it was 
> somewhat agreed upon as a good path to take.
>

i had pbuffers in 3dp at some point but i cut them out. (0.11 i think)
i don't remember why exactly. possibly it had to do something with 
threads & context switches i couldn't get to work right.

i'm planning to dig into this again soon..

you can do a lot with multipass rendering. i use this in 3dp
to fake a texture target: just render to a part of the buffer
as large as the tex, and grab it. it's fast & convenient.
the only drawback is that it doesn't work when the window is
obscured by another one, but i think there should be a way to
prevent this..