'Arthur and the Invisibles': Luc Besson's Animated World

The year 2006 was a banner one for feature animation in France. Arthur and the Invisibles joined the ranks of Azur and Asmar and the groundbreaking Renaissance. All images courtesy of The Weinstein Co./Europa Corp.

The year 2006 was definitely a great one for feature animation in France. Michel Ocelot, director of Kirikou and the Sorceress, released a new colorful, enchanting tale called Azur and Asmar, while Christian Volckman broke new ground with his stylish black & white Renaissance. The latest entry in the genre is directed by France's most popular filmmaker, Luc Besson, an artist better known for his live-action movies (The Professional, The Fifth Element) than for his interest in animation. Arthur and the Invisibles (which opens Jan. 12, 2007 in the U.S.) tells how 10-year old Arthur gets magically transported to the tiny world of the Invisibles, half-inch tall creatures who live in his grandmother's garden. Influential graphic album artists Patrice and Celine Garcia brought the project to Besson. The former had been a key element of the design team on The Fifth Element, and later became the lead conceptual artist for Arthur and the Invisibles.

Since the movie also featured live-action sequences, the world of the Invisibles had to look like it was part of our world. Besson didn't want to go from a real setting with real actors to a stylized environment à la A Bug's Life. The Invisibles were real beings living in a real garden, not fantasy creatures in a fantasy world. The filmmakers' plan was to create the characters via CG animation, and combine them with photoreal environments. The question of how to create these environments became the key issue, with the team testing multiple approaches over a period of two years.

Director Luc Besson's quest to create the characters via CG animation and combine them with photoreal environments brought him to Pierre Buffin (right) and his Buf Compagnie. Buffin worked on the project for almost six years.

A Blank Check to Start It All

To address these issues, Besson turned to Buf Compagnie, France's leading visual effects facility. For founder and 3D director Pierre Buffin, this marked the start of a journey that would last almost six years, including three years of full production. "We had to animate CG characters in more than 1600 shots," Buffin says. "So, the producers were really concerned about our capacity in this regard, as no one in France had ever attempted a project of this magnitude.

"They were asking us, 'Can you create animation for a feature film? How many animators will we need? How many Americans?' Besides animation, their main concern was, obviously, the cost and the duration of the project. Unfortunately, I could not give them any estimation. Without any reference, it was just impossible to evaluate how much it would cost and how long it would take. We didn't even know how we were going to make this movie at all, and I didn't want to be contractually tied up to a deadline and a budget that I wasn't certain I could meet."

Buffin continues, "We looked into the option of co-producing the movie, but I knew shot approval would become an issue, as this was Luc's movie. In the end, Luc took a bold decision. He gave us his green light to develop the technology and to create the 3D sequences... without any deadline or budget! It was basically a blank check... It was quite a gamble for him, and I knew it, but this mark of trust infused the team with an enormous energy and, in the end, the total cost turned out to be lower than expected."

The filmmakers decided to shoot a test featuring Arthur in motion. They first focused on the best possible way to create the environments. Using a full 3D approach was not an option for most of the shots, as this would necessitate a gigantic effort to make the CG settings look photoreal. Besson and Buffin agreed that the best look would be obtained by shooting real environments. The initial plan was to build the Invisible world at 1:1 scale, meaning that if a house was built in a nutshell, the crew would actually decorate a real nut.

Buf created the Invisibles interior environments at 3:1 scale, meaning that every plant, root, mushroom, nut, had to be built three times the size of the real thing.

The environment was then filmed with micro lenses that were small enough to sneak between blades of grass and capture the real world from the perspective of a half-inch tall character. The technique had its advantages, but it required so much light (100.000 watts) that the vegetation quickly wilted. Plus, depth of focus was difficult to maintain. "The obvious way to emphasize the tiny size of a character is to have the background out of focus, as this is the way insects and flowers are traditionally photographed," Buffin explains. "But Luc didn't want to use this approach. He told us: 'Imagine that the entire film crew had been reduced to the size of an Invisible, and that all our equipment -- camera, lenses, lights, etc. -- was at the same scale. I want to do it as if it were a traditional live action movie.' So, we decided to look into practical models."

Production designer Hughes Tissandier and model supervisor Gilles Boillot opted to create the Invisibles interior environments at 3:1 scale, meaning that every plant, root, mushroom, nut, had to be built three times the size of the real thing. Floral expert Valerie Arson managed to find scale equivalents between plants, which translated into live 23-inch tall grass blades. The crew first tried to shoot the model sets via motion control, but the technique was slow, cumbersome and provided footage that did not always suit the needs of the CG animators.

"Sometimes, the camera would move too fast for Arthur's little legs, or it would be a little bit too high," Buffin recalls. "Plus, it was very complex and didn't allow for much flexibility. That's where I suggested using photogrammetry. We've been developing this technique since the mid 1980s, being the first company to use it on a commercial project. It involves taking still photographs of a set - or prop - from every possible angle, and then use a proprietary piece of software to recreate the geometry of the set in the computer. By comparing the various perspectives, the algorithm is able to determine the geometry of the set in three dimensions. Once we have the 3D volume, we project the photographs onto their corresponding geometry, which provides us with a photoreal representation of the set.

"The main advantage of this approach is that it allows us to move the camera without any restriction, as the entire environment is now contained within the virtual world. For Luc, it meant that he could adjust his camera moves and framing quickly and precisely, as if he was on a live action set. It also meant that he was able to change shots during post-production, which he often did. He was not bound to motion control background plates. Luc is a very precise director in terms of the camera work. So, it was a huge improvement for him to eventually be able to keep on working like he always had."

"Video motion capture" was used on the performers to guide the animation. Unlike traditional motion capture, the actors don't wear any tracking marks.

From Practical Model to CG Model

Buf's team -- including R&D supervisor Xavier Bec, animation director Geoffrey Niquet and 3D producer François-Xavier Aubague -- developed the production pipeline that would be employed to create the shots. The first step was to build a "white model," an Invisible set represented in rough form without any decoration. Lit in flat light, the model was thoroughly photographed and rebuilt in the computer using photogrammetry. The digital set was then employed to previsualize the shots, based on the extensive storyboard drawn by Patrice Garcia. Early on, Luc Besson had been recorded while commenting each board and answering the team's questions, which enabled the artists to nail down the shots with minimum guesswork.

The 3D environment also helped determine where the openings would need to be on the model to gather the best material possible during the photo shoot. It also established which part of the set would actually be seen in camera, thus avoiding unnecessary and costly decoration work. Once the final configuration was determined, the art department built a fully detailed version of the model.

A team of 10 photographers and assistants gathered photographic references from the models, using a digital Nikon D1 still camera. Since the photographers were not familiar with photogrammetry, Buf provided them with 3D printouts that they simply needed to duplicate. The sets were mostly lit in a flat and neutral light, without any shadows or highlights. The lighting would be entirely created in the digital world.

"The scale was so small that it was difficult to light the sets and get the subtle look that Luc was after," Buffin says. "Plus, it allowed us to create the lighting for the characters directly, not for the environment only. Parallel to this photogrammetry effort, we were also modeling and texturing several exterior environments from scratch. All the garden shots were entirely created in 3D. The complexity of the environment and the necessity of animating the plants in the breeze made it logical to use a full 3D approach.

"To this purpose, our crew went to the garden that was used for the location shoot, and photographed every plant species that they could find. These were then recreated in 3D. The ground itself and the stream were also computer-generated." A few live action elements were photographed to be combined with the CG environments, including the waterfall and the water flowing in the tunnel. As always, Buf only used proprietary software for every step of the production process, except for the render engine, which was mental ray.

Initially the environment was filmed with micro lenses that were small enough to capture the real world from the perspective of a half-inch tall character. But when this technique failed, Buf turned to photogrammetry.

While the interior and exterior sets were being built in the computers, Buf and Besson set out to capture live performances to guide the animation. "We called it Video Motion Capture," Buffin notes. "It was not traditional motion capture as the performers didn't wear any tracking marks. I never liked motion capture. It only provides you with a maximum of 30-50 animation points, which was far from enough for our needs. Plus, the set-up can be quite cumbersome with all the tracking marks and cameras. What I suggested was using live performances as a guide for the animators. I thought that Luc would respond much strongly to a technique that would enable him to really 'animate' his characters via live performers.

"We simply shot the actors in front of 13 to 14 video cameras: six for the 3D animation, three to four to cover the action from different angles, two to three with a tighter framing, and one that was used by Luc to choose his camera angles. All along, we recorded Luc's comments and directions, as to help the animators get a better feeling of the purpose of each shot later on. The whole process lasted about 45 days. Then, Luc used this video footage to create a rough cut of the movie, which became our reference for the animation. He really enjoyed the process as it allowed him to combine performances from different takes or even from different characters."

Animating the Buf Way

All the 3D character models were derived from Buf's generic Human Body. The model comprised of a skeleton based on a human skeleton, with 336 muscles attached. A tool enabled the team to change the shape of this generic model and turn it into any character, even during the animation process: any modification on the model's shape, costume or accessories didn't compromise its animation as it was automatically reinitiated in all the shots. For facial animation, the team created a databank of expressions that were more or less accentuated from character to character. Each character also had a series of pre-animated mouth movements. The two were then blended, providing any kind of mouth shapes for any kind of expression.

Buf's animation software is rather unique, being based on an unraveling approach. "I don't like the feel of the animation that you get from off-the-shelf software," Buffin comments. "You often don't get the sense that the character has any weight at all. Our approach is more intuitive. The character sets his foot down, and we pivot the body around his foot until the other foot comes down. We then use other tools, such as gravity and dynamic, to perfect the animation.

"Since all our models stem from our generic Human Body, the animation could be applied to any character. It meant that we could take parts of the main characters animation to animated secondary characters or even crowds. It was a great asset on this project." An unexpected problem arose when it appeared that most of the animators were unable to form the proper mouth shapes for English dialogues! So, when the voice talents, including Madonna and David Bowie, were recorded, two video cameras captured the mouth movements in close-up to serve as a reference.

All the 3D character models were derived from Buf's generic Human Body. The team could change the shape of this model and turn it into any character, even during the animation process.

Ninety-five percent of the animation was created by young artists who were directly recruited in French animation schools. They went straight from their classroom to the greatest 3D animation project ever attempted in France! The gamble of hiring non-professionals ultimately paid off. "They were fresh, full of energy, and not attached on any particular piece of software," Buffin notes. "It meant that they could adapt to our specific set of tools much easier than a seasoned professional." Buf ultimately hired more than 100 young animators - the average age was 24 - who produced the animation over a period of 27 months. The whole crew was comprised of 225 people; none of them had ever worked on an animated feature film before.

For everyone involved, this project was a huge learning and enriching experience. "I'm very proud of what we achieved, given that none of us, including in production, had never done anything like this before," Buffin concludes. "I'm especially proud of the way we allowed Luc to shoot his movie and to direct his performers just like he would have done it on a live action set. It was such a relief for him. Altogether, this whole project turned out to be somehow easier than I thought it was going to be. The key part was preproduction, when we had to decide how we were going to do it. Luc was bold enough to let us make extensive tests, and in the end, the options that we took turned out to be the right ones. Once we started actual production, it all went surprisingly smoothly."

Alain Bielik is the founder and editor of renowned effects magazine S.F.X, published in France since 1991. He also contributes to various French publications, to VFXWorld, and occasionally to Cinefex. In 2004, he organized a major special effects exhibition at the Musée International de la Miniature in Lyon, France.