Ironically, this specific question also is an example of a cross-site duplicate of a question on Meta Stack Exchange: What to do with cross-site duplicates? But let's not get too meta here.
Basically, I agree with Robert Cartaino's and malach's answers in the mentioned MSE question.
So, if a question is appropriate here, we should keep it and answer it with the Computer Graphics background in mind. Depending on the specific question and other site, this may actually lead to different answers, or to answers which are similar but explain different aspects in more detail. Also, we could provide a link to the cross-site duplicate in a comment to give the user even more information.
This way, users who only know/found one site benefit from the information.
If the question is inappropriate here, we can migrate or simply close it.
However, identical questions, maybe even asked within a few minutes, by the same user, should probably be closed on sites where it doesn't belong and only answered on the most appropriate site. There are even more detailed information on Meta Stack Exchange (Is cross-posting a question on multiple Stack Exchange sites permitted if the question is on-topic for each site?)