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EIEF: NYU's Ken Perlin On 'Magic Emotions'

Following last year's EIEF presentation on procedural animation techniques, Professor Ken Perlin of New York University returned to Edinburgh by popular demand to demonstrate his latest research into engaging and emotive characters - we have full details.

August 23, 2006

4 Min Read

Author: by Ren Reynolds, Edinburgh

Following last year's EIEF presentation on procedural animation techniques, Professor Ken Perlin of New York University returned to Edinburgh by popular demand to demonstrate his latest research into engaging and emotive characters. The core of Perlin’s work is to establish a set of techniques whereby animated characters can become more emotionally expressive. He does this by layering a set of procedural animations onto models such as stick and joint skeletons. As he demonstrated, this technique has a number of advantages over other techniques such as animation loops. First, as the procedures operate on sub-parts of a some skeletal structure, the overall frame can be stretched or shrunk for tall or short characters, or even have bits removed such as a character with a missing limb. Second, as procedures can be blended into each other, shifting a character from walking to running, or giving a character a stoop and getting them to jog can be done without any glitches between animation sets, as the movement vectors of each procedure are simply being added to give the final result – all in real time, of course. Emotive Actors, Projected Emotions In his first demonstration, Perlin showed how Inverse Kinematics applied to simple models added a level of realism to their actions. Using a beer bottle borrowed from a member of the audience, Perlin demonstrated how the simple act of picking off the table involved a range of compensatory motions, such as shoulder dip, from other parts of the body. He added that while computer games today might see a character simply picking up a bottle and getting it to the mouth realistically as a success, the level that he wanted to reach would be able to portray a character reaching for the beer after being told by their best friend that they had been having an affair with their wife, and trying to make that movement seem unstressed. Showing his Fiend animation, Perlin explained that it was created with a very simple set of procedures all, apart from the blink, based on sine waves. The highly expressive and slightly disturbing creature has such an emotional impact on us, Perlin suggested, "because a lot of acting is projection" - that is, given very simple clues the audience will project emotions and inner narratives onto characters. Chords Of Emotion Reinforcing the point, he showed an older facial demo whose expressions can be controlled with sliders that alter just one degree of freedom. Each degree of freedom, Perlin explained, "is like a note which can be combined into chords." Again, Perlin stressed "it is suprising how little you need as the people watching will do the work," adding "as long as you don’t do anything egregious wrong." To demonstrate this, he showed the face completely still yet still posed in an expression, pointing out that the very slight movements added to each pose were what gave the face life. Next he showed a set of objects on the surface of a sphere, demonstrating that as the number increased, the less like individuals they seemed and the more like particles, adding that "acting is different when you have scale." On a similar theme, he showed what looked like a living fridge magnet poem, where similar techniques are used with words. Giving a glimpse behind the scenes, he revealed that each word is trying to get back into the order of the original sentence. Usability and Character Control Moving on to input and control, Perlin showed a character that he had earlier demonstrated being controlled with a musical keyboard, and how he had mapped notes to a standard qwerty keyboard. Demonstrating the way that emotion had been layered on top of simple movement in each of the procedures, Perlin stressed what terrible input devices a mouse and keyboard are for performance, adding that maybe software purposefully does this so we don’t ask computers to do too many things at the same time. The serious point to the demonstration was to show the methods Perlin is working through in which characters can be controlled and express complex emotions by layering simple tools usable by young children. Stressing the importance of character as a way of connecting with an animation, Perin demonstrated a set of characters he had created, as he felt each seemed to embody something about the animation problem he was trying to solve in trying to get people engaged. Examples of these included the Soap Duck that demonstrates spring dynamics; the hummingbird that demonstrates how humming birds fly, and the simply bizarre unicycle with an eye. Conclusion Perlin closed the session by showing a program intended to encourage children to learn to write code. The application features a walking musical note controlled by code that the user can alter, which, in real time, impacts the character's behavior. The goal, Perlin stated, was to get children "to think in programming space," the trick being that the Note has a character that people find engaging and want to interact with, but to do so, they must learn how to code it.

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