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Animated smiles: it's all in the detail

smiling eyes

The eyes have it: drawings of three sets of eyes show their changes as the person begins to smile. (Pic: Mr Eduardo Chavez)

Animated characters would be more realistic if programmers took more notice of how the eyes and mouth interact when smiling, an Australian student has discovered.

Mr Eduardo Chavez studied smiles and facial behaviour as part of his Master of Design research at the Faculty of Design, Architecture and Building at the University of Technology, Sydney.

He was inspired by the unconvincing smiles on animated characters in films such as Shrek and Final Fantasy. The latter was the first film to have a complete cast of animated humans.

"Even though these characters had been rendered very well, I found they were still lacking believability," said Mr Chavez, now working with the University's Faculty of Information Technology.

In a spontaneous smile, both the eyes and the mouth are activated. This is called a 'Duchenne smile', after the French researcher who studied smiles many years ago. In a fake smile, usually only the mouth becomes activated and not the eyes.

Mr Chavez set out to find out whether the eyes activate the mouth, or vice versa.

He randomly selected 10 students and filmed them while they watched a compilation of humorous videos. He then analysed the footage frame by frame — a time-consuming task, with the final tally reaching 27,000 frames.

The analysis was based on a measurement system that Mr Chavez created to grade the intensity of expression.

He found the eyes and mouth were not always activated at the same time.

"There are stages within a smile where the eyes and the mouth are not necessarily working in a synchronous manner," explained Mr Chavez.

"The eye and mouth are very complex and relate to each other in ways I'm only starting to understand."

In addition, the details of a smile involve movement of the head, the way muscles get activated, how the nose changes shape, and the change of skin tones as blood flushes the face.

This complexity probably explains why people are not yet able to create characters that are completely believable, said Mr Chavez. Animators have been looking at the overall expressions and behaviours, not the details, he said.

The research is not just about cartoons. Increasingly, software programs are using 'software agents' — computer-generated animated human faces that give instructions and respond in real time to what is happening.

"These agents are capable of producing animated expressions on the fly," said Mr Chavez.

Mr Chavez is considering furthering his research into facial expressions but would like to work with an organisation or individual who has a practical purpose for the research in order to focus the work.

His Masters research was jointly supervised by Dr Simeon Simoff from the Faculty of Information Technology and Dr John Broadbent from the Faculty of Design, Architecture and Building.