Adding a '3D print' button to animation software

Jul 31, 2012
G.I. Joe may have finally met his match. Photo courtesy of Moritz Bächer

(Phys.org) -- Watch out, Barbie: omnivorous beasts are assembling in a 3D printer near you.

A group of graphics experts led by at Harvard have created an add-on that translates video game characters -- or any other three-dimensional animations -- into fully articulated action figures, with the help of a 3D printer.

The project is described in detail in the Association for Computing Machinery (ACM) Transactions on Graphics and will be presented at the ACM SIGGRAPH conference on August 7.

Besides its obvious consumer appeal, the tool constitutes a remarkable piece of code and an unusual conceptual exploration of the virtual and physical worlds.

"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," explains lead author Moritz Bächer, a graduate student in computer science at SEAS. "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. You could even have a head that isn't attached to its body, or legs that occasionally intersect each other instead of colliding."

A new software tool translates animated character skins into action figures that can be produced on a 3D printer. Photo courtesy of Moritz Bacher

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 that's on the screen must be adapted to accommodate real-world constraints.

Bächer and his coauthors demonstrated their new method using characters from Spore, an evolution-simulation video game. Spore allows players to create a vast 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.

This video is not supported by your browser at this time.

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.

"As an animator, you can move the skeletons and create weight relationships with the surface points," says Bächer, "but the skeletons inside are non-physical with zero-dimensional joints; they're not useful to our fabrication process at all. In fact, the skeleton frequently protrudes outside the body entirely."

Adding a '3D print' button to animation software
Before and after. (Image courtesy of Moritz Bächer.)

Bächer tackled the fabrication problem with his Ph.D. adviser, Hanspeter Pfister, Gordon McKay Professor of Computer Science at SEAS. They were joined by Bernd Bickel and Doug James at the Technische Universität Berlin and Cornell University, respectively.

This team of computer graphics experts developed a software tool that achieves two things: it identifies the ideal locations for the action figure's joints, based on the character's virtual articulation behavior, and then it optimizes the size and location of those joints for the physical world. For instance, a spindly arm might be too thin to hold a robust joint, and the joints in a curving spine might collide with each other if they are too close.

The software uses a series of optimization techniques to generate the best possible model, incorporating both hinges and ball-and-socket joints. It also builds some friction into these surfaces so that the printed figure will be able to hold its poses.

The tool also perfects the model's skin texture. Procedurally animated characters tend to have a very roughly defined, low-resolution skin to enable rendering in real time. Details and textures are typically added through a type of virtual optical illusion: manipulating the normals that determine how light reflects off the surface. In order to have these details show up in the 3D print, the software analyzes that map of normals and translates it into a realistic surface texture.

Then the 3D 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 3D," says Bächer. "I think that's helpful to the artists and animators, to see how it actually feels in reality and get some feedback. Right now, perhaps they can print a static scene, just a character in one stance, but they can't see how it really moves. 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."

Bächer's model does not allow deformations beyond the joints, so squishy, stretchable bodies are not yet captured in this process. But that type of printed character might be possible by incorporating other existing techniques.

For instance, in 2010, Pfister, Bächer, and Bickel were part of a group of researchers who replicated an entire flip-flop sandal using a multi-material 3D printer. The printed sandal mimicked the elasticity of the original foam rubber and cloth. With some more development, a later iteration of the "3D-print button" could include this capability.

"Perhaps in the future someone will invent a 3D printer that prints the body and the electronics in one piece," Bächer muses. "Then you could create the complete animated character at the push of a button and have it run around on your desk."

Harvard's Office of Technology Development has filed a patent application and is working with the Pfister Lab to commercialize the new technology by licensing it to an existing company or by forming a start-up. Their near-term areas of interest include cloud-based services for creating highly customized, user-generated products, such as toys, and enhancing existing animation and software with these capabilities.

Explore further: Blu-ray disc can be used to improve solar cell performance

More information: dl.acm.org/citation.cfm?id=2335398

Related Stories

Cebit 2012: 3-D animations for everyone

Mar 06, 2012

3D movies like "Toy Story" or "Transformers" are based on everyday objects that are able to move like humans. Such 3D characters are created by skilled experts in time-consuming manual work. Computer scientists ...

The physics of animation

Jun 14, 2011

From drawings to computer animation, the magic of cartoon movies allows audiences to explore a fantastical and imaginary world. To make animated characters life-like on the big-screen, the laws of physics ...

Making 3D avatars the easy way

Dec 01, 2010

Researchers at the Technion-Israel Institute of Technology have developed a user-friendly method for creating realistic three-dimensional avatars (graphical representations of computer users) from any digital ...

Scientists use pixels to ease amputees' pain

Nov 14, 2006

Academics from the School of Computer Science and School of Psychological Sciences have developed a virtual reality system, which gives the illusion that a person's amputated limb is still there.

History in 3D

Nov 02, 2009

(PhysOrg.com) -- Three-dimensional computer graphics is moving into museums. Works of art are being digitally archived in 3D, simplifying research into related artifacts and providing the public with fascinating ...

Recommended for you

Enabling the hearing impaired to locate human speakers

17 minutes ago

New wireless microphones systems developed at EPFL should allow the hearing impaired to aurally identify, even with closed eyes, the location of the person speaking. This new technology will be used in classrooms ...

Researcher explores drone-driven crop management

23 hours ago

A flock of pigeons flies over the soybean field where J. Craig Williams is standing. He reaches down and rips off a brown pod from one of the withered plants and splits it open. Grabbing a tiny bean between ...

Wireless electronic implants stop staph, then dissolve

Nov 24, 2014

Researchers at Tufts University, in collaboration with a team at the University of Illinois at Champaign-Urbana, have demonstrated a resorbable electronic implant that eliminated bacterial infection in mice ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

ubavontuba
not rated yet Aug 01, 2012
That's too cool!

And, I bet it could have wide ranging applications in prosthetics!
antialias_physorg
not rated yet Aug 01, 2012
That's a pretty amazing piece of software. Writing the algorithm for the joints must have been tough. Combinnig collision detection, movement types and group exclusion is pretty clever.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.