I wrote my BA essay on virtual photography; screen grabs from virtual, computer generated, enviroments. I believe there's a strong case to be made that virtual photography is just that, photography, and not painting or sculpture which has also been suggested.
So far, I have yet to see any theoretical work on the subject (although the topics that are relevant in the definition of virtual photography have been well travelled by others long before me)
The essay was published after an exhibition at Gallery spark in Copenhagen in spring of 2005. if you wish to read the essay, you can download it here: vp.zip