A Short History of Computer Animation

Overview of Computer Animation

To 'animate' is literally 'to give life to'. 'Animating' is moving something which can't move itself. Animation adds to graphics the dimension of time which vastly increases the amount of information which can be transmitted. In order to animate something, the animator has to be able to specify, either directly or indirectly, how the 'thing' is to move through time and space. The basic problem is to select or design animation tools which are expressive enough for the animator to specify what s/he wants to specify while at the same time are powerful or automatic enough that the animator doesn't have to specify the details that s/he is not interested in.

There are two main categories of computer animation: computer-assisted animation and computer generated animation. Computer-assisted animation usually refers to 2D and 2 1/2 dimensional systems that computerize the traditional hand-drawn animation process.

Motion specification for computer-generated animation is divided into two categories: low level techniques (techniques that aid the animator in precisely specifying motion), and high level techniques (techniques used to describe general motion behavior) .

Low level techniques consist of techniques, such as shape interpolation algorithms (in-betweening), which help the animator fill in the details of the motion once enough information about the motion has been specified by the animator. When using low level techniques, the animator has a fairly specific idea of the exact motion that he or she wants.

High level techniques are typically models used to generate a motion using a set of rules or constraints. The animator sets up the rules of the model, or chooses an appropriate algorithm, and selects initial values or boundary values. The system is then set into motion, so to speak, and the motion of the objects is controlled by the algorithm or model. The model-based/algorithmic approaches often rely on fairly sophisticated computation, such as physically based motion control.

One of the things which distinguishes animation techniques is whether its the animator or the computer which bears most of the burden. Motion specification aids are those techniques which seem to require more input from the user and fairly straightforward computation. Model-based approaches, on the other hand, require less from the animator and more computation.

Another way to characterize the difference between techniques is to look at the level of abstraction at which the animator is working. In one extreme, at a very low level of abstraction, the animator could color in every pixel individually in every frame. At the other extreme, at a very high level of abstraction, the animator could tell a computer to 'make a movie about a dog'. Presumably, the computer would whirl away while it computes such a thing. A high level of abstraction frees the animator from dealing with all of the details. A low level of abstraction allows the animator to be very precise in specifying exactly what is displayed when. In reality, animators want to be able to switch back and forth and work at various levels of abstraction. The challenge to developing animation tools is designing them so that animators are allowed to work at high levels of abstraction when desired, while providing the ability to work at low levels when needed.

Perception

When animation is recorded for later viewing, it is typically presented in film or video formats by recording a series of still images. This is possible because the eye-brain assembles a sequence of images and interprets them as a continuous movement.

The receptors in the eye continually sample light in the environment. The only limitation on motion detection is the reaction time of those sensors and on certain mechanical limitations such as blinking and tracking. If an object moves fast enough, then

the receptors in the eye will not be able to respond fast enough for the brain to distinguish a sharply defined, individual detail; motion blur results.

In either film or video, a sequence of images is recorded which can be played back at rates fast enough to fool the eye into interpreting them as continuous motion. Of course, in order to save resources, this rate is kept as low as possible while still maintaining the persistence of motion. Under some viewing conditions such as room lighting and viewing distance, the rate at which single images must be played back in order to maintain the perception of motion varies. The image is said to flicker when the perception of continuous motion fails to be created. Objects appear as a rapid sequence of still images to the eye-brain.

There are actually two rates that are of concern. One is the number of images per second that are displayed in the viewing process. The other, is the number of different images that occur per second. The former is the playback rate; the latter is the sampling rate or update rate. For example, images are always played back at 30 images per second on a TV, but in some Saturday morning cartoons there may be only six different images per second with each image repeated five times.

In the Research Labs

Computer animation has been around as long as computer graphics. The University of Utah , funded by DARPA, was the early pioneer in computer graphics and produced many of the well-known names in graphics as well as most of the important early work in computer graphics. The seminal work in computer graphics is Ivan Sutherland's SketchPad system. This system animated line drawings on a screen by enforcing constraints in real-time. This is a form of model-based animation.

Also produced from the effort of the University of Utah were some early films on a walking and talking figure, an animated hand and an animated face. It has only been recently that this early work in animation has actually been eclipsed.

In the late sixties Chuck Csuri was doing some pioneering work in computer animation in the Computer Graphics Research Group at The Ohio State University. A major feature of the animation that came out of Ohio State in the mid-seventies was real-time video playback from a digital disk. The hardware that took the digital information, uncompressed it on the fly and converted it into a video signal was developed at North Carolina State University. In the early 80s, the research group became the Advanced Computing Center for Art and Design and continues to produce computer animation.

Norm Badler , at the University of Pennsylvania, was one of the first researchers addressing the problem of human figure animation. He has continued this research and has established the Center for Human Modeling and Simulation .

Also in the mid-seventies, at Cornell University , the Program for Computer Graphics generated some architectural walk-throughs of Cornell's campus.

In 1974, the first computer animated film called Hunger. This effort was a 2 1/2 D system that depended heavily on object interpolation techniques. Canada has been active in computer animation (and animation in general) due in large part to the National Film Board of Canada and the National Resource Council Canada .

NYIT got into graphics in a big way in the late 70s. They produced some incredible animation. Many of the people from the Utah effort contributed to the NYIT lab. The Works represents some of the early impressive pieces to come out of NYIT.

Computer Animation: Films and Videos

Early on, Computer Graphics (CG) appeared in a variety of movies in which it was used as computer graphics (that is, the CG was not intended to fool the audience into thinking it was anything other than CG). For example, Future World (1976) and Star Wars

(1977, Image West) fall into this category. More recently, Lawnmower Man (1992, Xaos, Angel Studios) which has a segment of Hollywood's view of Virtual Reality in it, used CG in the same role, although a more sophisticated example.

Tron (1982, MAGI) was a little different. The CG was still supposed to be computer-like because the action takes place inside a computer. But in this case, it was an integral part of the environment that the actions (and actors) were taking place in. The CG was used throughout the movie. It integrated computer animation with live action, but, since the action took place in a computer, the CG didn't have to look realistic (and didn't). This was the first time CG was used as an integral part of a movie.

Along the same lines of Tron in using CG to create an 'inside the computer' environment is Reboot (1995, Limelight Ltd./BLT Productions). Reboot deserves special mention as the first Saturday morning cartoon that is full three-dimensional computer-generated animation. The action takes place inside a computer so they don't have to go for 'realism'. Still, there are several human-like main characters and, overall, The Reboot series is very impressive.

One main uses of CG has been to replace physical models. In this case, CG is used to create realistic elements which are intermixed with the live action. The Last Star Fighter (1984) used computer animation instead of building models for special effects. The action takes place in space as well as on planets; CG was used for the scenes in space and physical models were used for the scenes on a planet. It's not hard to tell when the movie switched between CG models and physical models. There were probably 20 minutes of CG used in the movie. This was the first time CG was used as part of the live action in which it wasn't supposed to look computer generated. More recently, Apollo 13 (1995) used CG models of the return vehicle from the mission. In TV-land, special note should go to Babylon 5 (1995, Newtek). Babylon 5 is the first TV show to routinely use CG models as regular features of it's sci-fi show - and it's Amiga-based.

CG is also used to create 'alien' creatures. Creatures which are supposed to be realistic, but don't have to match anything that the audience is familiar with. The Abyss (1989, ILM) is one such movie in which CG is used to effect an alien creature which is integrated with the rest of the live action. Some of the CG in Terminator II served a similar purpose as well as Casper (1995, ILM).

More challenging is the use of CG to create realistic models of creatures that are familiar to the audience. Jurassic Park (1993, ILM) was the first to completely integrate use of CG character animation in which the graphics were designed so as to blend in with the live action so that it was difficult to tell what was computer generated and what wasn't. Jumanji (1995, ILM) does the same thing with it's incredible modeling of animals. To a lesser extent, Batman Returns (1995, Digital Domain) also does the same thing by providing 'stunt

doubles' of Batman in a few scenes. CG was used to create the face of RoboCop 2 (1990, deGraf/Wahrman) and animated skeletons in Total Recall (Metrolight) as well.

Another popular CG technique for special effects is the use of particle systems. One of the best examples is in Star Trek II: The Wrath of Khan (LucasFilm computer division, later ILM) in which a wall of fire sweeps over the surface of a planet. Another example is Lawnmower Man in which a character disintegrates into a swirl of small balls. A more recent example from television is in the opening sequence of Star Trek: Deep Space Nine (1995) to model a comet's tail. Twister also uses particle systems to simulate a tornado.

Of course, one use of computer animation is simply to 'do animation.' Meaning that computer animation is used to produce animated pieces which would otherwise be done by more traditional means - essentially 3D cartoons (although the term cheapens the idea somewhat). The Pixar animations have been previously mentioned. Technological Threat was an early animation that combined computer animation with hand-drawn animation to produce an entertaining piece. TV commercials, for the most part, fall into this category. Some popular ones come to mind: Listerine, Shell dancing cars, and LifeSavers. Toy Story (1995, Pixar, Disney), the first full length fully computer-generated 3D animation, would fall into a category of 3D cartoon. Absolute realism is not the objective as much as doing a computer-generated version of what would normally be done by traditional animation means. The previously mentioned 2 1/2 D Hunger would fall into this category, as would the TV episode of The Simpsons (1995, PDI) in which Homer turned into a 3D CG character and the TV special Incredible Crash Dummies (Lamb & Company).

Morphing is essentially a 2D procedure which warps control points (or feature lines) of one image into the control points (feature lines) of another image while the images themselves are blended. In Star Trek IV, one of the first commercial morphs was provided by ILM in the back in time dream sequence In Willow (1988, ILM), ILM provided the morph of several animals. This technique was also used by ILM in Indiana Jones and the Last Crusade (1989) and Terminator 2 . PDI is known for its use of morphing in various commercials including a Plymouth Voyager commercial and an Exxon commercial in which a car changes into a tiger. Of course, morphing has gone on to become another Energizer Bunny of TV commercials - it keeps going and going and going... Full 3D morphing has yet to make it out of the research labs and into any production environment.

There is another class of movies in which CG plays a role - that of 'hidden special effect' (for lack of a better term). CG can be used to cover up mechanical special effects or to enhance the scene to integrate a mechanical special effect more completely. However, with the onset of digital techniques for 2D compositing, sequences will be routinely digitally available making them susceptible to a variety of digital post-processing techniques. The first digital blue screen matte extraction was in Willow (ILM). The first wire removal was in Howard the Duck (ILM). In True Lies (1994, Digital Domain), CG was used to erase support wires from suspended actors. In Forest Gump (1994, Digital Domain), CG was used to insert a ping pong ball in a sequence showing an extremely fast action game. In Babe (1995, Rhythm & Hues), CG was used to move the mouths of animals and fill in the background uncovered by the movement. In Interview with a Vampire (1994, Digital Domain), CG was used to curl the hair of a woman during the transformation into a vampire. In this case, some of the effect was created using 3D graphics and then integrated into the scene by 2D compositing.

Computer Animation:Study Questions

1. What are the two main categories of computer animation?

2. Define low and high level techniques of animation.

3. What does a high level of abstraction allow the animator to do?

4. What is the difference between playback rate and sampling rate?

5. Who was the early pioneer in computer graphics-what was produced?

6. What’s the major feature developed in the 70’s? Descibe the feature.

7. What is the importance of the film “Hunger”?

8. What was the early use of computer graphics?

9. How were computer graphics of “Tron” different from previous ones?

10. Why is the animation “Reboot’ significant?

11. What was one of the main uses of computer graphics?

12. What is the most challenging use of CG?

13. What was the importance of the animation “Technological Threat”?

14. What is morphing? Provide an example from a movie made recently.

15. What are some other useful purposes of CG?

A Short History of Computer Animation

Computer Animation:Study Questions