Daniel Radcliffe used a Cameron Diaz photo as CGI reference point on Harry Potter

Working with CGI and green screens can be a challenging task. For starters, where are you even supposed to look if the computer-generated dragon isn’t next to you? For Daniel Radcliffe, it was at a picture of Cameron Diaz.

Tom Felton, who played Draco Malfoy in the Harry Potter series, has recounted an amusing anecdote from behind the scenes of the fantasy series. Instead of always using tennis balls as reference points–that is, a guide for where the actor should look so it is more natural on screen–the cast was allowed to bring in their own personal items. “After a while they gave us more individual objects to stare at. We chose pictures of something or somebody close to our hearts. Daniel Radcliffe had a picture of a particularly beautiful Cameron Diaz.”

Felton recalled this in his book, “Beyond the Wand: The Magic and Mayhem of Growing Up a Wizard”, which came out this week. Tom Felton, for what it’s worth, used a picture of a carp, which he described as “even more beautiful.” We’re not so sure about that, but hey, it’s your book, Tom!

Tom Felton provided some other visual effects secrets in the book, chiefly related to the Quidditch games, which had to be shot in a room completely covered in green and blue so the filmmakers could create the atmosphere of flying through the air.

Daniel Radcliffe has said he has no interest in reprising the role of Harry Potter. “I’m getting to a point where I feel like I made it out of Potter, okay and I’m really happy with where I am now, and to go back would be such a massive change to my life.” However, now that Cameron Diaz is coming out of retirement, that might entice him into hopping back on the broomstick…