Of mice and models: artists create realistic digital mice for a TV ad campaign.(UK television commercials for Aero candy)

A series of UK television commercials for Aero candy stars some extremely talented digital mice who sing, dance, and even hula-hoop. Despite their efforts, the mice fail to impress chocolate buyers and scurry away dejected. The ad campaign began with a 30-second commercial featuring one hula-hooping mouse, who is joined in a second spot by dozens of others, including one that sings Chinese opera and performs an elaborate, oriental-style dance. The most recent spot, which is expected to air soon, contains a group of mice performing a complicated Irish step dance.

Creating these gifted photorealistic creatures and giving them naturalistic movements required a similar amount of talent and ingenuity on the part of the modelers and animators at digital effects house Glassworks and animation production company Passion Pictures, both located in London. According to Alastair Hearsum, head of 3D at Glassworks, the computer generated mouse in the film Stuart Little set a high standard against which the audience would judge the Glassworks character. For its Aero mouse, though, Glassworks chose a different tack by dispensing with the character's clothes and opting for a more realistic approach compared to the stylized Stuart in terms of appearance and movement.

"The challenge was to create a mouse that the audience believed was real," says Hearsum. "It had to move like an actual mouse, and have realistic proportions and features."

The 3D animations of the mice were inspired by 2D pencil drawings from Passion's visual effects director Chris Knott and animation directors Tim Watts and Alyson Hamilton, who had collected various mouse images before making character drawings. The duo worked closely with Hearsum to produce the convincing personalities of the mice. Glassworks then constructed the mice models, added realistic fur, and animated them to move under Passion's guidance and direction within a live-action environment.

"There are no complicated rigging setups, layered expressions, or complex shaders with the exception of the fur," notes Hearsum. "But that's not to say that the project wasn't challenging. One of the more difficult aspects was getting the mice to look sweet and move in simplistic yet charming ways." This was accomplished, in part, by using a fairly blank facial expression for all the creatures, so they wouldn't look anthropomorphic, despite their humanlike actions.

Mouse Modeling

Whether a scene has one mouse or a hundred, each character originated from the same model, which Hearsum built with separate NURBS patches using Softimage|3D running on an SGI Octane system. He then constructed a complex skeletal structure for the model, whereby the skeletal parts that were controlled by inverse kinematics (IK), such as the arms and legs, would be limited to two connecting joints. With this structure, the shoulders were not part of the arms, but linked to them as parents rather than children in the chain. That setup, combined with the vector constraints, gave the group total control over the movement of the arm and shoulder, for example, and eliminated rotational or other range-of-motion issues that can occur when multiple joints are interconnected within the bone structure.