Besides being a wonderful feature film, "The City of Lost Children" ("La cité des enfants perdus") by Marc Caro and Jean-Pierre Jeunet also combines traditional computer animation and visual effects in a high quality project. The rendering of the film and the combination of computer animation and live action outline today's possibilities in computer animation in an extremely impressive way.

No one in France had made a full length film with so many different kinds of special effects ever before - direct, CGI and digital: 144 out of 800 shots, 17 minutes, one fifth of the entire film. BUF Compagnie did the CGI of "The City of Lost Children". In its ten years of existence, BUF Compagnie has gained a solid reputation in the creation of 3D computer generated special effects and had a long record of professional contact with Jean-Pierre Jeunet and Marc Caro. They both have a taste for adventure, and the both had it fot "The City of Lost Children".

Flea

Pulex irritans, a reddish brown insect that lives as a parasite on human blood, growing to all lengths - up to 4 mm - and merrily jumping all over the set, hungrily sticking its stinger into anyone who happens to cross its path.


What's this flea made of anyway? It's not an electronic model, not a digitized photo, it's a cute little chimera concocted in C. G. I., modelled, dreaded, and animated by his creators at the Buf Compagnie, using a mythological method of mathematics that took hundreds of hours on the computer.

The surface texture was obtain-ed by using several layers of lovely materials such as beach pebbles, green beans, snake skin, pig skin, leather, etc. The animators studied hours and hours of documentary films to find out how fleas act out there in nature. Now they know everything about how fleas hop, skip, jump, land, sting and drink, and do scores of dirty itchy tricks that have earned them a worldwide reputation.

Given the variety of shots where the flea would star, the animators modelled a series of fleas with varying degrees of definition. The most sharply defined had no less than 800.000 polygons. And yet these were not the most serious complications caused by the flea; getting him to look right and act right was nothing compared to the difficulties of fitting him into the image. No matter how real the flea looked, it would all be spoiled if it seemed like it was stuck onto an artificial decor. How could they go from a wide shot to a closeup of the flea? At that time there was no available program that could take into account the depth of the field. So the engineers wrote one in the space of three short months!

Dream Bottles

For this character Caro wanted a green-color-slightly-luminous something that looked like smoke, visions of troubled faces, and speeds varying from 'slow and hesitating' to 'fast'. Again, there were no programs available that could handle that kind of smoke. So Buf Compagnie did a made-to-order program in three months. It's a kind of particle system, in which each particle acts like a particle of smoke. But smoke is capricious and the program had a tendency to make real smoke. So they had to add about thirty parameters to domesticate that smoke. A single image of smoke requires one or two hours of calculations and the final result can only be judged on the basis of calculations for the whole shot, so it's easy to understand why the dream-as-a-character as the most difficult element finally turns out to be the most delightful surprise.

Another problem with smoke is that you can see through it. Well, that dream in smoke goes past barred windows, skips across floors and puddles, etc. So the common solution of using a matte was excluded. To get the effect of smoke passing over all those different surfaces, they had to model the whole setting in three dimensions based on decorator's drawings and measurements made on the set and then do an image-by-image rotoscopy of all the shots where the dream would be cut in.

Metamorphosis of Krank and Miette

This touching scene where Miette grows old as Krank grows young took so much time to prepare that it was put at the very end of the shooting schedule. First the casting office tried to get doubles of the actors at different ages: younger and younger for Krank, older and older for Miette. Then Buf Compagnie took a try at morphing the doubles, going from one to the other, to pick out the most convincing combinations. Having the little girl grow old was no problem. But everything they tried for rejuvenating Krank was disastrous. So all through the metamorphosis, they had to keep some of the facial morphology and use the expression in the eyes of Emilfork, the actor who plays Krank.

For this effect, his face was modelled in stereophotogrammetry. As Krank and Miette metamorphose, Krank's laboratory is distorted, although this is hardly noticed by viewers, because their attention is focussed on the changes in the characters. Nevertheless, this distortion required complete three-dimensional modelling of the laboratory, based on decorator's blueprints.

The photos by the set photographer Eric Caro were scanned and flashed on to the model by mapping. So the set disorts without losing volume even when parts of it are invisible.