Started off with a take home test, which they emailed me. Seems to be the same question as the other posts.
Following this, we scheduled a Skype interview about a week after my submission. Interview was with their Director of Engineering. It started off with questions about my background and resume projects. He then asked if I had any questions and we had a chat about specifics of their engine design. It was finally topped off with a couple simple questions. One was about writing a unit test and other was an old-school graphics question in basic C.
They decided to fly me out a week later and put me in a hotel. On site interview started off with a tour of the office and then led to about 3~4 hours of technical interviews. I talked with various graphics engineers for about an hour each, with a lunch interview in between.
Everyone was super nice and a pleasure to talk to.