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 3D modeling, 2D 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. © 1997 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 3D 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 2D 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 one 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 2D information in order to create or support a 3D 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 2D technique. The effects teams involved in James Cameron's Titanic, made incredible use of this technique to create some very subtle effects.