Hi list,
Cyrille wrote me a reply off-list meanwhile:
hello Peter, my mail was rejected from the list, I don't know why, so I just forward it to you so you have my answer, even if it's not yet on the list.
[...]
from pix_snap2text help file : "When banged [pix_snap2tex] will take a snapshot of the current render buffer and immediately texture it to any geometric object attached. You can specify the close-up you want to be grabbed via offset/dimension-pairs." So, if you [t b a] it, you render it's current buffer before any snapshot. So, you basically render whatever garbage is in the GPU memory. if you [t a b] it, assuming you already render something in the render buffer, things will works as expected : you snap the render buffer, and then render it.
So, it's not a bug. You just need to put a [t a b], just like in the help file!
Thank you Cyrille, the explanation makes sense. With the suggested [t a b] order I do not get visual feedback as I would with [t b a]. There is also no effect of chaning the render order of the two gemheads to render the teapot before or after the snapshot.
best, P