the (ugly) solution i use is to rchange the position of the camera to
render and record just a small part of the image.
doing this many time gives you lot's of images that you can add together
to have a very big image.
here is the abstraction i use.
thank you very much, it works, although I will have to do some changes
to my patches. I am using random values that change everytime I trigger
render. (that was not a good method anyway...). and montage takes quite
a long time.
I also ran into a new bug of pix_write, but that's another mail.