I’ve been to see Disney’s Tangled twice now. It’s a fantastic animated movie – funny, thrilling and heartwarming. For me, its supreme achievement is to take the traditional Disney movie formula of fairytales, princesses, true love and following your dreams; and present it all with a freshness and vigour that makes it suddenly seem relevant and captivating to modern audiences without parodying itself or backtracking for one moment on the fact that it really, really is a Disney movie.
Tangled is also very well presented in 3D and it’s one of the first 3D films I’ve seen to make great use of the Floating Window to expand the possibilities of its shot design and prevent Edge Violations. So it seemed like a good opportunity to take a look at the technique and how it’s been used in Tangled.
If you’re making a film in 3D you can choose to present the scene behind the screen or in front of it. If things are behind the screen they are said to have positive parallax and the screen will seem like a window through which you can view objects far off in the distance. If things have negative parallax they appear in front of the screen and hence you can make objects come into the movie theatre and make the audience try and reach out and grab stuff. However, if objects with negative parallax move toward the edge of the picture they can get cropped off by the edge of the screen. This creates what we scientists call an Edge Violation – the 3D thing on the screen suddenly looks wrong because it’s behind the edge of the screen, even though it looks like it’s in front of it. This is uncomfortable for the audience to view and could collapse the suspension of disbelief and pop them out of the movie.
The Floating Window is a very simple technique to remedy the problem. The idea is to insert a very narrow black bar down one side or other of the 3D picture in just one of the stereoscopic eyes. The effect is that suddenly the vertical edges of the frame seem to be closer than they actually are – as if the screen itself moved closer than it really is. You kind of have to see this to believe it works, so next time you see a 3D movie try taking your glasses off and checking out the edges of the frame at left and right. Here’s a pretty neat video that explains the technique quite well if you’ve got a pair of red/blue anaglyph glasses to hand.
Tangled make a lot of use of Floating Windows in all sorts of interesting ways. The main use is just to make compositions comfortable to view which would otherwise be difficult or impossible to reconcile with 3D. For instance in a classic over-the-shoulder shot like this you really want the subject (Rapunzel, on the right) to be composed on the screen with the character on the left in the foreground with negative parallax in 3D. However that creates a horrible edge violation with the left of the screen, as the foreground character appears like a kind of disembodied cut out blob with a face and shoulder. The conservative thing to do is to just compose the entire shot with Rapunzel deeper into screen so the foreground character is either on or barely in front of the screen, but some stereographers I know have even said “Don’t do over the shoulder shots at all!”. This is pretty dumb, because we really want to do over-the-shoulder shots – we want to put the audience in the circle of action and feel like we’re part of the emotional space. In the example above imagine if we couldn’t see the character on the left at all – the image would lose all its emotional context since we can’t see who Rapunzel is actually looking at. The solution to the problem in Tangled is to put a Floating Window on the left of the screen so the screen edge seems to be every so slightly in front of the foreground character and we just aren’t bothered by the edge violation. Voila!
But Tangled does some other pretty neat stuff with Floating Windows. Firstly, they’re animated so they will change from shot to shot and even move slightly during a shot. It’s slightly surprising to realize that the edges of the screen can jump around like this and no one in the theatre notices!
But Tangled was also using Floating Windows to ease compositions that weren’t actually creating edge violations at all. In a shot like this they might use a floating window on the left of screen so the foreground character doesn’t feel like he’s leaping off the screen and protruding into the theatre, even though he’s not breaking the edge of frame. They would also happily use different Floating Window depths on the different edges of the screen. So again in this example there might be a Floating Window on the left, but not one on the right. Again the bizarre thing about this is that it just works and no one in the theatre seems to care that the sides of the picture are bouncing all over the place; although maybe Roger Ebert is having a fit somewhere.
The other really, really cool thing Tangled did though is to use diagonal Floating Windows. Now, I’m not 100% sure about this because although I saw the movie twice I didn’t get a good enough look at this to be totally positive because it’s kind blink-and-you-miss-it; but it looked like in some cases the Floating Window was at an angle, so the bottom of the window seemed to be closer than the top. So in a shot like this the Floating Window solves the Edge Violation at the bottom, but leaves the top unaffected. I’ve certainly never seen this before on any other movie, and again it’s surprising that the effect apparently isn’t noticeable to the film-going public.
So as we’ve seen the Floating Window is a pretty awesome technique to help you compose shots in 3D and expand the possibilities for storytelling without melting the audience’s brains. It’s worth noting two things however: first this only really works in a movie theatre, not on TV or anything. A TV screen usually has a plastic bevel around its edge, so its impossible to fool the audience into believing that the edge of the screen is anywhere other than where it really is in depth. However, this isn’t such a problem since the small screen is a bit more forgiving that a massive cinema screen. A movie theatre will also need to be well set up so the edges of the screen are totally black and there’s no intrusive objects around the screen edge like exit signs to give you a depth cue that defeats the effect.
Secondly, there’s a significant problem with projectionists cutting the floating windows off when they screen the movie. Even though the movie is projected digitally, projectionists frequently apply the wrong settings and slightly crop the image at left and right, which of course cuts off the floating window completely. When I saw Monsters vs. Aliens a few years back there was no floating window at all, despite the fact I know for certain DreamWorks applied this effect to the film.