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French animated film flies high thanks to Inria

Yellowbird feather Imagine research team

"Yellowbird, ready for take off" (French title: "Gus, petit oiseau, grand voyage") was released on 4 February. Beneath the surface of this contemporary cartoon, the 3D animated film took many long months for animation studio TeamTO to produce, working in association with Imagine, the Inria project team based at the Grenoble - Rhône-Alpes Research Centre. Jean-Baptiste Spieser, TeamTO Technical Director, and François Faure, Professor at Grenoble University and researcher in the Imagine team, explain.

How did TeamTo and Inria come to work together?

Jean-Baptiste Spieser : We met a little over two years ago through Imaginove, the digital industry competitiveness cluster in the Rhône-Alpes region. We at TeamTO were looking for a way to improve the quality of our physical animation… The Imagine team had the skills and expertise that could help us do this: so we asked them to help us develop new tools tailored to our needs.

To begin with, we didn't think of working together on Yellowbird , since it was on the point of going into production. But in the end we advanced faster than planned…

François Faure : Even though our collaboration was pretty slow getting off the ground. At the start, we had to change how we work - research takes time, something that is not exactly compatible with an animated film production schedule!

Yellowbird poster TeamTo & Haut et Court

For Yellowbird , the partnership focused on the feathers of the main characters. Why were these feathers such a challenge for TeamTO?

J.-B. S. : The problems we ran into were mainly to do with the film's graphical style, which is highly stylised, rendered to look something like crumpled paper, with feathers that look like the scales of a pangolin*. On paper, it looks easier to create these feathers in 3D than produce a realistic representation. Unfortunately, although there are tools for modelling real feathers, like in the film Rio, there is nothing for scales. Our feathers also needed to be consistent across the whole wing surface and react credibly to the different mechanical forces to which the characters are subject, without any visual aberration. And we needed all this without expecting our animation artists to be computer geniuses. So, we needed a new tool, designed to deal with all these constraints.

What was Inria's input in this respect?

F.F. : Within our team, we are working on Sofa, a physical simulation software tool originally designed for medical simulation. For Yellowbird , a light version of Sofa was connected to Maya, TeamTO's 3D animation platform. This enabled them to control the feathers intuitively, from rigging (i.e. creating all the individual parts of the 3D objects) through to the animation stage.

Do you have any further plans to work together?

J.-B. S. : Sofa is now totally integrated in Maya, and we have started to work with Inria on new issues, such as animating hair and clothing. Also, we have started work on another joint project regarding a new animation software tool within the framework of a partnership with Mercenaries Engineering. Inria is working on the physical simulation engine for this project.

*A small, toothless, insect-eating mammal, whose elongated body is largely covered with scales.

Birth of a feather

With an average 1,500 feathers per bird, around twenty different kinds of bird and scenes involving up to a dozen characters… the animation studio's problem with the feathers was not to be taken lightly! In Yellowbird , the graphics processing chosen by Art Director, Benjamin Renner, required each feather to be processed individually. The problem was that each feather entails complex physical motion depending on the bird's movements, its mass and the effects of the wind, as well as contact with the feathers next to it. Even if the visual style is that of a cartoon, the birds' movements have to look believable.

“To solve this complex equation,” explained François Faure, “we used a mass-spring model. This approach enables the simplest representation of any deformable matter, reduced to a set of particles linked together by springs to which all the forces impacting on movement that you want to recreate can be applied. This type of model makes programming much simpler, resulting in perfectly consistent visual rendering.”  A total of 20 people at TeamTO worked on the feathers.

Keywords: Yellowbird Feathers TeamTo SOFA INRIA Grenoble - Rhône-Alpes Movie Animated movie Modelling Imagine team

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