Rigging Your 3D Models In The Real-World

3D Real-World Rig

Computer animation is a task both delicate and tedious, requiring the manipulation of a computer model into a series of poses over time saved as keyframes, further refined by adjusting how the computer interpolates between each frame. You need a rig (a kind of digital skeleton) to accurately control that model, and researcher [Alec Jacobson] and his team have developed a hands-on alternative to pushing pixels around.

3D Rig with Control Curves

Control curves (the blue circles) allow for easier character manipulation.

The skeletal systems of computer animated characters consists of kinematic chains—joints that sprout from a root node out to the smallest extremity. Manipulating those joints usually requires the addition of easy-to-select control curves, which simplify the way joints rotate down the chain. Control curves do some behind-the-curtain math that allows the animator to move a character by grabbing a natural end-node, such as a hand or a foot. Lifting a character’s foot to place it on chair requires manipulating one control curve: grab foot control, move foot. Without these curves, an animator’s work is usually tripled: she has to first rotate the joint where the leg meets the hip, sticking the leg straight out, then rotate the knee back down, then rotate the ankle. A nightmare.

[Alec] and his team’s unique alternative is a system of interchangeable, 3D-printed mechanical pieces used to drive an on-screen character. The effect is that of digital puppetry, but with an eye toward precision. Their device consists of a central controller, joints, splitters, extensions, and endcaps. Joints connected to the controller appear in the 3D environment in real-time as they are assembled, and differences between the real-world rig and the model’s proportions can be adjusted in the software or through plastic extension pieces.

The plastic joints spin in all 3 directions (X,Y,Z), and record measurements via embedded Hall sensors and permanent magnets. Check out the accompanying article here (PDF) for specifics on the articulation device, then hang around after the break for a demonstration video.

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Real-time digital puppetry

digital_puppet_show

If it sometimes seems that there is only a finite amount of things you can do with your kids, have you ever considered making movies? We don’t mean taking home videos – we’re talking about making actual movies where your kids can orchestrate the action and be the indirect stars of the show.

Maker [Friedrich Kirchner] has been working on an application called MovieSandbox, which is an open-source realtime animation tool. A couple of years in the making, the project is cross-platform compatible on both Windows and Apple computers (with Linux in the works), making it accessible to just about everyone.

His most recent example of the software’s power is a simple digital puppet show, which is sure to please young and old alike. Using sock puppets fitted with special flex sensors, he is able to control his on-screen cartoon characters by simply moving his puppets’ “mouths”. An Arduino is used to pass the sensor data to his software, while also allowing him to dynamically switch camera angles with a series of buttons.

Obviously something like this requires a bit of configuration in advance, but given a bit of time we imagine it would be pretty easy to set up a digital puppet stage that will keep your kids happily occupied for hours on end.

Continue reading to see a quick video of his sock puppet theater in action.

[via Make]

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Puppet Circuits

This isn’t a specific project, so much as a pointer to a budding new site. Puppet Circuits is the project of [Raphael Abrams], one of the co founders of NYC Resistor. As you can probably guess, he has been posting about the circuits he uses in his animatronic puppets. I faces all kinds of problems since may of the systems are to be worn and have to endure some pretty rough treatment and still perform well. Very interesting stuff to read about.

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