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Eye animation is crucial, but costly and difficult - Image Metrics

When it comes to creating believable characters, "the eyes have it" according to Image Metrics' Nick Perrett

A lot of the realism in today's videogame characters come from the eyes, says Image Metrics' Nick Perrett.

"I've really noticed this in videogames characters because, generally speaking, the eye animation is either non-existent or terrible," the VP of business development told

"The minute that the eyes aren't engaging, you start looking at the lip sync. Everybody, especially in the games industry, is obsessed with lip sync.

"But there is an element of me that says, actually, if you get the eye animation right, and the eyes are engaging...If we were standing in front of each other now, I wouldn't be staring at your lips."

The reason that developers want to continue to push the issue of realism is because of the story-telling opportunities it allows them to create - harnessing a human performance and delivering it through a complete fantasy environment.

Cost is definitely a key factor in why eye animation isn't done properly, but that's not the only issue involved.

"Part of the problem is that gross eye movement is not what makes the eyes. It is actually all the subtle little flicks."

Keyframing eye animation is prohibitively expensive, and motion capture can't really be used to get convincing eye data.

"You are stuck at video because video is the one thing where you can actually track pupil and iris movement, and pupil dilation even if you wanted to - because humans actually pick up on that as well. Certainly, emotions like love or fear trigger quite significant pupil change," Perrett noted.

The question becomes - even once eye data can be captured - how do game developers take advantage of it in a pipeline in a way that makes sense?

"If you are not doing simultaneous capture, then it becomes fiendishly difficult to use the eye data. Because if we are filming voice over sessions, of course the actor is not necessarily going to be looking where you want them to look - there is a direction issue there.

"A lot of it comes down to, not only is it fiendishly expensive, but there are technical hurdles and performance-related issues that prevent you from using the data properly, even if you could get it."

Getting detailed eye animation correct just isn't a priority with all of the other development issues.

"A lot of the time the priority just goes into getting the eye lined right - having characters properly look at each other. That's a big enough problem in and of itself," Perrett said.

The complete interview with Nick Perrett is now online.

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