Computer animation at Lucasfilm – Page 2

Using this method the computer only animates the background. All the characters are done by conventional animation. There for there is no time saving involved. The chances of wanting to do a whole story film by this method seem remote but it could be used for selected scenes in the same way that the multiplane camera has.

When John Lasseter arrived at Lucasfilm, William Reeves had already been working with the computer division there for four years. Reeves studied mathematics at the University of Waterloo and of Toronto and received a Msc. Computer Science in 1976, and a PhD. in 1980. His masters research studied the implementation of interactive computer graphics in a minicomputer environment. His doctoral research studied representations of complex dynamic shape for computer animation and motion analysis. The motion analysis work was to aid in cardiovascular research. The work also led to some new techniques for computer based inbetweening that was published in ACM SIGGRAPH in 1981.

In 1980 he joined the Computer Division of Lucasfilm and since 1982, he has worked full time in the graphics group as project leader of the modeling and animation group. In 1982 he invented a new image synthesis technique, called particle systems, that enables the generation of very complex and detailed images. Prior to working on The Adventures of Andre and Wally B. he had done computer animation for Star Trek II, The Wrath of Kahn and Return of the Jedi.

One of the scenes in Return of the Jedi required a planet to burst into flames, as seen from the window of a passing space craft. Reeves created the scene by computer. To give a convincing effect to the flames it required them all to be different to each other. This was achieved by getting the computer to generate many thousands of random numbers and then using these to plot the positions of the flames.

When it came to creating the tree covered hillsides for Andre and WaIly B. the flame generation programme was adapted to create 46,253 different trees. Once the position of the trees, branches and even leaves had been mapped out in the computers memory it could then use this information to draw the scene from any viewpoint. Thus when the viewpoint goes from a view across the valley to ground level the whole scene is actually redrawn for each frame of film. New calculations are made for every position on the screen, for example the point at which a branch starts and the point at which it ends in relation to the position of the viewer, or in mathematical terms its relationship to the axis of rotation. This would be a mind boggling task for a human but a routine task for a computer, given the right programme to work with. Other textures of the scene were built up in a similar way to the trees by adapting the programme to give the required look. So you get individual blades of grass, various flowers, a texture to the valley path and so on.

The Adventures of Andre and WallyB produced by Lucasfilm.

While this environment was being created, Lasiter was designing the characters of Andre and Wally B. They were constructed with a multitude of spheres, cones and cylinders. John Lasseter explained this with a slide showing the build up of Wally B’s feet. They were described as a tear drop. This was formed by a large sphere at the toe end, a small sphere at the heal end and three cone sections curving round to join the two. This is the kind of information that can be put into the computer with mathematical formula, a job for a computer programmer rather than an animator. But once it is in there it can be identified with a code name or number entered by the animator. When the animator is working out the character movement the character is drawn on the monitor screen with a very basic framework to speed up drawing time. The full detail is added at the filming stage. This method of working also has the advantage that a less powerful computer can be used at the planning stage. The finished programme can then be run on a large mainframe computer for speed during filming.

Lasseter pointed out some of the design points of Andre to show the kind of detail that was achieved. The soles of his shoes had a pattern like that of tennis shoes. One of his socks had a red stripe while the other had a blue one. To top it all his red fez style hat had the names of all the people who worked on the film embroidered around the hat-band in gold thread.

The computer image had been photographed from a monitor screen with a 35mm movie camera. The resulting image projected on the large screen of the viewing theatre looked excellent and it was only after they had pointed out the way it had been produced that I realised that TV scan lines were discernible. They said that they could have used laser output scanning to give even better results but they hadn’t done so for this particular test.

For those interested in hardware the equipment used on Wally B. by the Lucasfilm animators was three Digital Equipment Corp VAX 11/ 750s and one 11/780 of their own, ten 1 1/750s at Project Athena of MIT and one Cray XMP-2 and one brand new XMP-4 at Cray Research Inc. Average drawing time for each frame was five minutes on the Cray but they believe they can halve this with more development. Other equipment included Adage/Ikonas 32-bit frame buffers, Evans & Sutherland Picture System II vector display, Hitachi tablets, Fujitsu Egal winchester disk drives and Control Date Corp removable disc drives.

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Printed in Animator Issue 14 (Winter 1985)

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