Saturday, October 06, 2007

Good, Thankless Effects: "Stealth"

The first in the FXRant series, "Good, Thankless Effects."

"I'm addicted to visual speed," says director Rob Cohen in an interview with Popular Mechanics. If Mr. Cohen went to a 28-day rehabilitation clinic for his dependence on 'visual speed,' then maybe "Stealth" could have been a better film.

"Stealth" (2005)
, directed by Mr. Cohen, is a ridiculously bad movie. The plotting, story and characters are as childish as a Chuck Norris action flick from the '80's. Its central theme, the struggle between humanity and robotics, is as old as science fiction itself, and this garbage-film adds nothing to the mythology of this classic theme. But there are some really good visual effects in the picture, and with a bit of directorial restraint, the film could have easily been something unforgettable.

The most successful visual effects shots from "Stealth" are those of the futuristic stealth bombers landing, taxi'ing, and taking off from seabound aircraft carriers.

For all intents and purposes, these shots look and feel completely photoreal. There are no tip offs or visual cues to lead the audience to believe that these shots are anything other than natural, in-camera work. For all we know, the filmmakers got their hands on some amazing new military planes, and is cooperating with the military on the making of the movie. Of course, the reality is that these futuristic jets don't exist in the real world.

Special effects supervisor John Frazier did, in fact, build a full scale mockup to be placed on a gimbal for bluescreen photography, and also for some insert shots of actors getting out of the fighters. But the vast majority of the stealth fighter shots feature a fully CG plane, created by Digital Domain, under the supervision of veteran effects supervisor, Joel Hynek.

Completely realistic CG planes are nothing new; however, what makes these aircraft carrier shots in "Stealth" special is that the background photography is extremely naturalistic. The camera moves effortlessly around the planes; the shots don't 'feel' like effects shots, since the camera moves are part of the film. Even the shots of the fighters taking off and landing have pleasant camera choreography. Probably the single biggest advancement in the quality and plausibility of visual effects shots in the digital age is the relative simplicity of camera matchmoving complicated live-action camera moves. The ability to recover the precise placement and pan/tilt information from the film camera has allowed visual effects shots to graduate away from lockoffs and stilted motion control moves. Now, it's completely normal for a visual effects film, even one with hundreds or even thousands of shots, to not have a single true lockoff or motion control setup.

The shot shown above is a great example of the kind of naturalistic camera movement and choreography of which I'm referring. One of the stealth fighters takes off from the aircraft carrier, with the camera traveling along a parallel path. Notice how the fighter isn't precisely framed exactly in the center of the frame; the camera operator is either a little bit ahead of the action, or a little bit behind. This is exactly what happens in real photography. The operator knows that the plane will accelerate very quickly and take off, but the operator doesn't know exactly how fast it will happen. Plus, the operator is making many micromoves per second to get the best framing possible. All of these tiny cues are there in this "Stealth" shot. Either the production shot an empty plate and a clever animator did a brilliant job animating the jet within the frame, or the production photographed an actual fighter jet taking off (then erased the fighter jet and put the stealth fighter in its place), which would give the shot a built-in amount of spontaneity. Either way, this naturalistic camera choreography really helps sell the illusion.

As the bombers take flight, the synthetic planes move through entirely synthetic environments. Digital Domain made some huge strides on this visual effects tool, significantly advancing their terrain and cloud generating techniques. The process allowed them to create hundreds of flying shots without needing to rely on actual aerial photography.

Creating actual photographic backgrounds for aerial shots can be an expensive, frustrating process. It doesn't matter how much previsualization you have prepped before shooting starts; shooting plates in the air is a difficult, expensive process, and inevitably you have to make a lot of sacrifices. Getting all the coverage you need can cost a fortune, and unless you have another plane to photograph (or at least something in the frame for reference), you are shooting empty plates and hoping that something can be pieced together once all the film gets scanned. Even if you get aerial backgrounds you like, your animators are forced to work within that frame; if they have an idea for some other kind of movement, you'll either have to reconstruct new portions of the frame, or shoehorn the animation into your plate. And, in the case of a film like "Stealth," the speeds involved are simply too large to get in-camera, which makes retiming the footage inevitable, which adds a whole new slew of potential problems to the mix.

Going 100% virtual with the environment frees filmmakers of these limitations. With a purely CG world, you can move your camera anywhere you want-- fly around canyons, fly through clouds, create the exact valley necessary to support your animation. etc. Unfortunately, because we can move the camera however we want, it places a heavy responsibility for the virtual cameraperson to fly plausible flight paths and to create animation and choreography that is believable.

And this is where "Stealth" stumbles. 100% synthetic environments, no matter how brilliantly rendered or art-directed, can seem small and wrong with bad camera choreography and animation. With each scene, Mr. Cohen raises the stakes, and the velocity, and the visual effects just can't keep up. Cameras whip and tumble around the planes in acrobatic paths, so implausible they make the virtual cinematography for "Spider-Man" and "Van Helsing" look serene. The ridiculousness-meter continues to rise as the film progresses, with staggering implausibility, dopey character choices, and just plain darn childish storytelling.

Unfortunately, intermixed with Digital Domain's fine shots are several with odd motion blur issues - mainly, faked, small shutter angle motion blur. This is usually how this situation arises:

director: So in this shot, the planes are going 400mph, and the camera is rotating around the plane, zips to the second plane, zooms in then zooms out, all in less than four seconds.

effects supervisor: Um, okay. That's really fast, and a lot of choreography happening in a short amount of time, but we'll make it work.

Two months later, with the director looking at the first rendered versions of the shot, complete with accurate motion blur.

director: Whoa! That looks great! I love the energy! But it's too streaky, too blurry.

effects supervisor: Yes, but that's what would really happen in real life. The shutter is open, and in that short amount of time while the film is being exposed, the camera has traveled about 255 feet, so you'll get some streaking. We can reduce it a bit, but if we go too far, it will look staccato and, well, fakey.

director: No, no, no it won't. I need the audience to be able to read the action. Kill the motion blur. It will be awesome!

Wrong, Mr. Director, it will look like a video game. You really want your visual effects work to match your the photography in your film, and unless you're deliberately shooting your film with a small shutter angle ("Saving Private Ryan," "Gladiator"), you're going to want to match that standard, 180 degree shutter angle with your visual effects shots. Yes, there will always be times to tweak it, either reducing it or even increasing it, for effect. But a kinetic shot without accurate motion blur will stick out like a sore thumb. You can even see this in a few of the clips in the Digital Domain show reel (scroll down). Notice in some of the 180 degree whip pan shots that when the pan is at its fastest, you can still see crystal clear detail in the clouds.
On balance, the shots that take place with only the sky and clouds as backgrounds work well, whereas the shots that have the planes zooming close to the earth are less successful, probably because of the tough-to-swallow speeds involved. In general, the compositing of these sequences is top notch, particularly with the cockpit POV shots, and the transitions into live-action photography of the actors performing on a mock cockpit.

Another one of the more successful action scenes in the film is the fuel explosion ring sequence. I really like the choreography and character of the explosions, circling around the ring like a predator, toward our hero. There's a real sense of menace and impending doom, and the fireballs themselves appear dangerous yet plausible.

Ultimately, "Stealth" fails as a film because of its sophomoric storytelling and its director's addiction to "visual speed." And the visual effects would have been absolutely stellar had the director shown some restraint in both the shot count (some effects sequences are far too long) and the sheer velocity of the choeography.

Digital Domain's show reel for "Stealth:"

For further reading:

Please read an update to this post: "FXRant: A 'Stealth' Followup"

1 comment:

Ian said...

A brilliant post. Please continue this series!