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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Seeed Studio shows off their wares

Everyone’s favorite Open Hardware store – Seeed Studio – was at Maker Faire this last weekend. They showed off a bunch of cool toys, oscilloscopes, Arduino shields and other hardware goodness, but one of the more interesting products was from their B Squares line.

As [Colin] from Seeed showed us, each B Square is a small plastic enclosure about the size of a drink coaster. The corners of these squares are clad in metal, and each one has magnets inside. The idea behind the B Squares system is to provide power to other B Square boards via magnetic connections.

So far, Seeed has released an Arduino square, battery, solar, and LED squares, as well as iPod docks and prototyping boards. These boards can also be orthogonally, meaning it’s entirely possible to turn six B Squares into a B Cube.

These magnetic connections only provide power connections; there is currently no way to transfer data between different B Squares. We suspect, though, that anyone wanting to replicate the Apple MagSafe power adapter and invent a magnetic I2C bus would find these boards perfectly suited to the task.

Video after the break.

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Zen rock garden table uses magnets and sand

[Nick] is working on a prototype of a coffee table sand plotter that draws patterns in sand a lot like a zen rock garden.

[Nick]‘s zen rock garden uses a magnet to draw a ball bearing across the sand in interesting patterns. The build uses 3D printed gears and laser cut parts to rotate the table around and move the magnet along a radius of the circle. During the first test of the prototype, the ball bearing jerked around but this problem was solved by adding a piece of foam under the sand. Power is supplied through a slip ring in the base, and the table is controlled through Bluetooth.

Speaking of magnet-and-ball-bearing zen coffee tables, we ran across this video of a more professional-looking prototype that was the basis for a successful Kickstarter campaign. Like [Nick]‘s prototype, the entire build relies on magnets and a ball bearing to move sand around in patterns. Because this zen table uses an XY axis instead of [Nick]‘s polar setup, drawing logos is a lot easier math-wise, lthough it doesn’t look quite as cool as a circular rock garden.

After the break you can see these zen rock garden coffee tables in action.

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Beginner Project: Super Cheap Magnetic Mixer

[wesdoestuff]‘s mother needed a clean way to mix together fragrance oils. Being the stand up kinda guy he is, [Wes] threw together a few spare parts to make this Magnetic Stir Plate.

The whole setup is amazingly simple. Pry the fins off of an old computer fan, glue a couple magnets to the fan’s hub. Drill a hole for a DC connector, find some sort of cover and.. Bob’s your uncle! [Wes] advises that you test the spacing of the magnets on the hub before gluing them permanently, as they can be a bit tricky to align.

The stir bar for non food items is  a magnet bar from one of those crazy magnet and ball bearing toys, it is basically just a solid magnet covered in plastic.  Food safe bars can be acquired, though they are not as cheap.  With all that room under the hood we would love to see him throw in some kind of a PWM speed control but that could be a bit complicated. Most of us could throw this together from spare parts.  Video after the jump!

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Rodent-based power generation

Your hamster lives to good life, with food delivery and a maid service that cleans up after him. [DanF] helped to brighten up this hamster’s life even more by improving its exercise equipment and giving it a small night-light as well. This project adds a low RPM alternator to the hamster wheel.

The first part of the process was to reduce energy lost to friction by fitting the wheel with a bearing. From there a ring of permanent magnets was added which will pass by a stationary coil and induce a current. It works, but unfortunately there’s not enough power generated to charge a battery. That means the light is only on when the hamster is running. But maybe you can figure out a way to use a super-capacitor like we saw in that exercise bike hack.

One nice finishing touch to the setup is a bicycle computer to track how much time was sent on the wheel, and the distance traveled.

[Thanks Dizzy]

Engineering with magnetic spheres

We would imagine these experiments were spawned by a devastatingly boring day at the office. [Sparr] found himself the proud owner of one thousand rare-earth magnets and decided to see what geometric shapes he could build with the spheres. These are gold-plated N35 Neodymium magnets that measure just 6mm across. He discovered that every structure is built from rings of magnets with shapes dependent upon what sequence of increasing or decreasing members are used. What he’s done is visually pleasing but we’d like to try it ourselves to see how resilient each structure ends up being.

[Sparr's] post is from the Freeside Atlanta blog, a hacker space collective. [Curbob], a regular with the group, tipped us off that a few hacker conventions are coming up in their area and they’re looking for speakers for one-hour talks about projects. If you’re near Raleigh or Atlanta this is your chance to show off that ridiculously complicated project you’ve been risking your marriage to complete.

A Stirring Hack

Stirring Flask

[Oleg] of Circuits@Home and maker of the USB Isolation Board and the USB Host Shield has a new, two-part hack for his chemistry set. In Part 1 of  this hack, [Oleg] discusses the method he uses to make a stir bar spin and what types of stir bars work the best. Part 2 discusses the motor control code and circuit. Given the ample amount of capability leftover in the Arduino he used, we would like to see this stirrer paired with a heating element to have a complete hotplate/stirrer. What do you think you could do with or to improve this device?

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