Animated Action Figures


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A tool developed at Harvard can turn animated characters into physical action figures, according to a group of graphics and computer experts who developed the software to do it.

The software translates video game characters—or any other three-dimensional animations—into fully articulated action figures with the help of a 3-D printer.

"In animation you're not necessarily trying to model the physical world perfectly; the model only has to be good enough to convince your eye," said Moritz Bächer, a Harvard graduate student in computer science. "In a virtual world, you have all this freedom that you don't have in the physical world."

"You can make a character so anatomically skewed that it would never be able to stand up in real life, and you can make deformations that aren't physically possible," Bächer added. "You could even have a head that isn't attached to its body, or legs that occasionally intersect with each other instead of colliding."

Returning a virtual character to the physical world therefore turns the traditional animation process on its head, in a sort of reverse rendering, as the image on the screen must be adapted to accommodate real-world constraints, he added.

The new software optimizes the virtual model (top) and creates strong, articulated joints for 3D printing (bottom). The product emerges fully assembled. Image courtesy of Moritz Bächer.

Bächer and his team members demonstrated their new method using characters from Spore, an evolution-simulation video game. Spore allows players to create a range of creatures with numerous limbs, eyes, and body segments in almost any configuration, using a technique called procedural animation to quickly and automatically animate whatever body plan it receives.

As with most types of computer animation, the characters themselves are just skins—meshes of polygons—that are manipulated like marionettes by an invisible skeleton.

The team of computer graphics experts developed a software tool that identifies the ideal locations for the action figure's joints, based on the character's virtual articulation behavior and then optimizes the size and location of those joints for the physical world. For instance, a spindly arm might be too thin to hold a large joint, Bächer said.

The software uses a series of optimization techniques to generate the best possible model. It also builds some friction into these surfaces so that the printed figure will be able to hold its poses. Then the 3-D printer sets to work, and out comes a fully assembled, robust, articulated action figure, bringing the virtual world to life. "With an animation, you always have to view it on a two-dimensional screen, but this allows you to just print it and take an actual look at it in 3-D," Bächer said.

"I think that's helpful to the artists and animators, to see how it actually feels in reality and get some feedback. If you print one of these articulated figures, you can experiment with different stances and movements in a natural way, as with an artist's mannequin," he said. "Perhaps in the future someone will invent a 3-D printer that prints the body and the electronics in one piece," Bächer added.

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In animation you’re not necessarily trying to model the physical world perfectly; the model only has to be good enough to convince your eye.

Moritz Bächer, Harvard graduate student, computer science

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November 2012

by Jean Thilmany, Associate Editor, Mechanical Engineering Magazine