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LEGO hacker Philo Hurbain needed a way to model some of the more complex LEGO parts for use in the LDraw LEGO CAD program. Most LEGO parts are easy to model, but something like the tiny LEGO frog, shown above, is a little more tricky. Philo's solution: a 3D scanner made entirely of LEGO, save for a needle that's used as the probe.
I am a LDraw parts author, and as such I am always interested to find new ways to model LEGO parts. Many parts have a clear geometric structure and are relatively easy to create, but parts like the frog pictured above have no defined geometric shape and are very difficult to model. I toyed for a while with the idea of a 3D scanner... The solution came with 2008 LEGO Technic sets that include a new part, the linear actuator. These nifty device convert the rotation movement of a motor into a linear movement. Coupled with the high resolution of NXT encoder, I had all the elements to build a 3D scanner, precise enough for my purpose.
...The probe module (red/yellow) moves the probing needle back and forth as well as up and down. When the probe needle touches the object, the location of the contact point is recorded. The object module (white/blue) is able to move back and forth the object and rotate it. All the movements combined provide either a cartesian or a cylindrical scan.
If you're interested in making one of these, Philo has posted the MLCad files for the device, the pbLua source that operates the NXT brain, and instructions for turning the scan coordinate log into a usable mesh.
