Director David Cronenberg asked the Twilight star to appear in a full-frontal shot in the new drama, in which he plays billionaire money manager Eric Packer.
Pattinson admits he was tempted to go through with the request, but he eventually decided against it.
He tells European newspaper Metro, ""Five minutes before we filmed, David told me, 'I want to see the bottom of your balls on the top of the frame.'
""At the moment (of filming), I reminded myself that I would do anything for him. I went back to see him and told him that wouldn't happen. He took it really well. At the start, it's a very bizarre scene that you won't see again in another movie, I promise.""