Animation World Magazine, Issue 3.2, May 1998

Rotoscoping in the Modern Age

by Marian Rudnyk

Editor's Note: Due to legal restrictions at Paramount, this article contains a limited selection of images from the film, Titanic.

Visual effects, these days, can take on many varied forms. Far beyond the classic effects model work of legends such as Ray Harryhausen, today's effects can involve anything from complex scale and sub-scale model work to digital 3-D modeling, 2-D compositing and digital rotoscopic animation. Quite often the simplest visual element in a movie, discounted as real, can actually be the product of extensive visual effects work. This is especially true in the visual effects-driven movie world where rotoscoping can play an important role.

The sinking Titanic. © 1
997 Paramount Pictures and
Twentieth Century Fox.
All rights reserved.

In big-budget Hollywood films, visual effects are de rigueur. From the splashy effects in the Star Wars saga re-issues or Jurassic Park and The Lost World to the story-serving and subtle yet stunning effects of James Cameron's Titanic, we not only wonder at what's real and what's not, but now expect to see new and innovative visual effects. A Twentieth Century Fox/ Paramount film of massive proportions, Titanic is the stand-out example of the future of effects work. From what is assuredly some of the most elaborate model work ever done for a movie to the extensive work in digital 3-D CGI (computer generated imaging), Titanic is replete with cutting edge visual effects. Among its CG effects are the first ever truly realistic "digital ocean" or "digital water," virtual stunt extras created in CG, and state-of-the-art use of motion tracking. This is not to mention all of the breathtaking work done surrounding the actual ship itself. Some of the most subtle visuals, however, were also CG-based and involved extensive use of techniques based in traditional animation.

The giant set of Titanic. © 1997 Paramount
Pictures and Twentieth Century Fox.
All rights reserved.

Rotoscoping Then and Now
Rotoscoping is a process which involves tracing stages of movement from live-action film, to attain a realistic motion in animation or visual effects. Unlike the rotoscoping done in traditional cel animation (most recently evident in Twentieth Century Fox's Anastasia), the roto work in Titanic served a related but different purpose. Traditional animation rotoscoping is used to heighten or accentuate movement by imbuing it with a more life-like quality. Usually this is accomplished by first filming scene elements in live-action form, that mimic the intended movement within the animated film to be produced. Once filmed, say a scene with a couple dancing, animators trace off each frame, often in silhouette, and then "apply" this to their animated characters. The effect makes the animation literally come to life. The danger, however, in using this technique, is that often scenes that are rotoed stand out from others that are developed "by hand."

In the 2-D digital, or CG world, the idea of movement is still critically important. Compositing is the process by which separate film elements, like footage of a landscape and footage of a spaceship, are combined to form the final seamless image of the spaceship flying over the landscape. Rotoscoping has become an integral part of the compositing process. Though digital artists still need to worry about animating, they are now not so involved in character work as they are in a process called matting. In its simplest form a matte can be nothing more than a blocked part of a film frame; a protected area that is later filled with an element not in the originally shot footage or from whatever effects work will be done to the rest of the image. Mattes are an integral part of compositing. The exceptions are computer "click-and-fills," where the computer can be simply told to fill in any area of a given color, or value, with a given element. For example, "Fill in all white areas with water.' In digital rotoscoping, one is doing much more than a simple green or blue screen type effect, which in and of itself is actually nothing more than a basic compositing effect.

Digital rotoscoping uses 2-D information in order to create or support a 3-D effect. An animated matte is created and used to block, or protect, a specific film element so that a 3-D composite can be achieved using a 2-D technique. The effects teams involved in James Cameron's Titanic, made incredible use of this technique to create some very subtle effects.

Creating Breath
Some of Titanic's most delicate effects were created by visual effects and digital animation powerhouse Blue Sky|VIFX, a division of Twentieth Century Fox. Blue Sky|VIFX was charged with three basic types of shots for Titanic: those depicting the ship's immense engine room, star fields, and puffs of human breath which were critical in conveying the cold temperatures on the night of the ship's sinking. Despite their realistic subtlety, Titanic's breath sequences posed many technical challenges. Among them were the sheer number of puffs of breath that needed to be created and integrated into a staggering number of shots, all with a consistent quality that maintained the integrity of a given sequence while conforming to an over-all whole: the movie itself.

Actors spent much of the
filming time wet and probably
chilly, but simulated cold breaths
still had to be added to the final footage.
© 1997 Paramount Pictures
and Twentieth Century Fox.
All rights reserved.

Filmed near the relatively warm waters of the Pacific, many of Titanic's shots lacked the frosty breaths that were surely present when the liner went down in the ice-chilled waters of the North Atlantic in 1912. The challenge was to add these breaths using 2-D compositing, yet still have them appear "3-D". To accomplish this a variety of digital technical teams were assembled, among them a group of digital rotoscope artists.

The first task at hand was to acquire breath elements. These were shot using "breath actors". These breaths were then scanned by computer and assembled into a breath library. With the actual film shots in hand, the work of marrying the two into one could begin. To create the effect or illusion of 3-D each shot had to be individually evaluated for placement. Would the breath, for example, come out of a person's mouth, but be in front of one person yet in back of another? Complicating things further was the fact that as a given person's head turned, the breath's 3-D placement would also need to change. Critical as well, was the selection of the correct breath. Was it affected by wind, as in the shots of the sailors in the Titanic's crow's nest? Additionally, James Cameron wanted "breaths that act." In other words, breaths that would accentuate the dialogue or action. This meant extra special attention was required to fulfill this unique vision. It was such unparalleled attention to detail that would become Titanic's hallmark. With the shot evaluated and the breath(s) selected, the meticulous job of digital rotoscoping could begin.

The Process
If, for example, the given breath needed to go in front of someone or something, that was relatively easy because the breath could simply be "slapped" over the given area. Usually, though, that same breath would have to also fall behind, say, someone's moving shoulder. The compositor, or the digital rotoscope artist, would have to create an animated matte that exactly followed the movement of this shoulder, covering it to its precise edge. If the head turned then perhaps still more mattes would have to be created. Each matte, a tracing of the image element it was protecting, would then be rotoscoped to move exactly as did that image element, i.e. the shoulder. To accomplish this type of roto matte a digital artist typically sets up a series of key frames, much as a traditional animator does. The computer can then, by calculation, interpolate the necessary inbetweens. Unfortunately, this interpolation was not always completely "on." This would require a digital artist to go manually through and key every frame. Not precisely locking down an animated or rotoscoped matte could lead to a jittery element or effect, such as a breath, that would appear incorrectly placed among the shot's digital layers.

In Titanic, some of the most challenging rotoed scenes were the close-ups of Jack and Rose, where even a slight roto error would easily become evident. This was also true of some of the deck scenes, where many rotoed mattes had to move not only correctly, but allow for placement of both breaths as well as a night sky filled with stars. Once fully rotoed, breaths placed, and mattes removed, compositors could then proceed to adjust any number of parameters including breath speed, density/opacity, as well as any necessary color-corrections.

Perhaps this epic effects-laden movie's greatest effects legacy is not all the compositing, or rotoscoping, or 3-D modeling, etc. that was done. It is not the effects themselves that are what's important. What is most important is the story. Effects are there to serve story. More than any other movie before it, Titanic illustrates this best. Yes, one can have incredibly stunning, hauntingly beautiful, or even explosive visual effects, but if one doesn't serve the story with these effects, use them to bring the story to life without overpowering it, then all one has is effects. When the effects stand behind the story and serve it, then one has a film that stands as a milestone in the effects industry.

Venture back to the
November 1996 issue of Animation World Magazine to read an interview with James Cameron about his work on the Terminator 2-3D stereoscopic 3-D ride for Universal Studios.

Marian Rudnyk is a former NASA astronomer and planetary photogeologist who worked at the Jet Propulsion Laboratory in Pasadena, California. He was part of NASA's PCAS (Planet Crossing Asteroid Survey) Program where he was an asteroid hunter. He also participated as a member of NASA's Achievement Award winning multi-mission imaging team on the Voyager at Neptune mission, as well Magellan at Venus and many others. Making a transition into the animation industry, he began as a traditional animator freelancing on such projects as a Levis commercial for Acme Filmworks. He currently works as a digital artist, science consultant and freelance writer. He has written for the World Book Encyclopedia and David Wallechinski's People's Almanac of the 20th Century. His current film credits include Titanic, Home Alone 3, and Armageddon.

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