A Motion Capture System For Everyone

[Chordata] is making a motion capture system for everyone to build and so far the results are impressive, enough to have been a finalist in the Hackaday Human Computer Interface ChallengeIt started a few years ago as one person’s desire to capture a digital performance of a dancer on a stage and has grown into a community of contributors. The board files and software have just been released as alpha along with some instructions for making it work, though more detailed documentation is on the way.

Chordata motion capture dancer and BlenderFifteen sensor boards, called K-Ceptors, are attached to various points on the body, each containing an LSM9DS1 IMU (Inertial Measurement Unit). The K-Ceptors are wired together while still allowing plenty of freedom to move around. Communication is via I2C to a Raspberry Pi. The Pi then sends the collected data over WiFi to a desktop machine. As you move around, a 3D model of a human figure follows in realtime, displayed on the desktop’s screen using Blender, a popular, free 3D modeling software. Of course, you can do something else with the data if you want, perhaps make a robot move? Check out the overview and the performance by a clearly experienced dancer putting the system through its paces in the video below.

As a side note, the latest log entry on their Hackaday.io page points out that whenever changes are made to the K-Ceptor board, fifteen of them need to be made in order to try it out. To help with that, they show the testbed they made for troubleshooting boards as soon as they come out of the oven.

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Light Painting Animations Directly From Blender

Light painting: there’s something that never gets old about waving lights around in a long exposure photo. Whilst most light paintings are single shots, some artists painstakingly create frame-by-frame animations. This is pretty hard to do when moving a light around by hand: it’s mostly guesswork, as it’s difficult to see the results of your efforts until after the photo has been taken. But what if you could make the patterns really precise? What if you could model them in 3D?

[Josh Sheldon] has done just that, by creating a process which allows animations formed in Blender to be traced out in 3D as light paintings. An animation is created in Blender then each frame is automatically exported and traced out by an RGB LED on a 3D gantry. This project is the culmination of a lot of software, electronic and mechanical work, all coming together under tight tolerances, and [Josh]’s skill really shines.

The first step was to export the animations out of Blender. Thanks to its open source nature, Python Blender add-ons were written to create light paths and convert them into an efficient sequence that could be executed by the hardware. To accommodate smooth sliding camera movements during the animation, a motion controller add-on was also written.

The gantry which carried the main LED was hand-made. We’d have been tempted to buy a 3D printer and hack it for this purpose, but [Josh] did a fantastic job on the mechanical build, gaining a solidly constructed gantry with a large range. The driver electronics were also slickly executed, with custom rack-mount units created to integrate with the DragonFrame controller used for the animation.

The video ends on a call to action: due to moving out, [Josh] was unable to continue the project but has done much of the necessary legwork. We’d love to see this project continued, and it has been documented for anyone who wishes to do so. If you want to check out more of [Josh]’s work, we’ve previously written about that time he made an automatic hole puncher for music box spools.

Thanks for the tip, [Nick].

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3D Printering: When an STL File is Not Quite Right

STL files are everywhere. When there’s something to 3D print, it’s probably going to be an STL. Which, as long as the model is good just as it is, is no trouble at all. But sooner or later there will be a model that isn’t quite right in some way and suddenly project progress hits a snag.

When models interface with other physical things, those other components may not always be exactly as the designer expected. Being mindful about such potential inconsistencies during the design phase can help prevent problems, but it’s not always avoidable. The reason it’s a problem is because an STL file represents a solid model as a finished unit; it is not really intended to be rolled back into CAD programs for additional design changes.

STL files can be edited, but just like re-modeling a component from scratch, it can be a tricky process for those who don’t live and breathe this stuff. I’ll describe a few common issues related to STLs that can hold up getting that new project together, along with ways to deal with them. Thanks to 3D printing becoming much more commonplace, basic tools are within reach of even the least CAD-aware among us.

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You’d Print A Part, But Would You Print A Foot?

Born with just one foot, [Nerraw99] had to work around prosthetics all his life. Finally getting fed up with the various shortcomings of his leather and foam foot, he designed, tweaked, printed and tested his own replacement!

After using Structure Sensor to scan both his feet, [Nerraw99] began tooling around with the model in Blender and 3D printing them at his local fablab/makerspace: MakerLabs. It ended up taking nearly a dozen printed iterations — multiple printing issues notwithstanding — to get the size right and the fit comfortable. Not all of the attempts were useless; one version turned out to be a suitable water shoe for days at the beach!

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Decorate Your 3D Prints with Detailed Hydrographic Printing

It’s like the old quip from [Henry Ford]: You can have your 3D prints in any color you want, as long as it’s one. Some strides have been made to bringing more color to your extruded goodies, but for anything beyond a few colors, you’re going to need to look at post-print processing of some sort. For photorealistic 3D prints, you might want to look into a simple hydrographic printing method that can be performed right on a printer.

If some of the prints in the video below look familiar, it’s because we covered the original method when it was presented at SIGGRAPH 2015. [Amos Dudley] was intrigued enough by the method, which uses computational modeling of complex surfaces to compose a distorted image that will be stretched back into shape when the object is dipped, to contact the original authors for permission to use the software. He got a resounding, “Nope!” – it appears that the authors’ institution isn’t big into sharing information. So, [Amos] hacked the method.

In place of the original software, [Amos] used Blender to simulate the hydrographic film as a piece of cloth interacting with the 3D-printed surface. This allowed him to print an image on PVA film that will “un-distort” as the object is dipped. He built a simple tank with overflow for the printer bed, used the Z-axis to dip the print, and viola! Photo-realistic frogs and globes.

[Amos]’ method has its limitations, but the results are pretty satisfying already. With a little more tweaking, we’re sure he’ll get to the point that the original authors did, and without their help, thank you very much.

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My DIY BB-8: Problems, Solutions, Lessons Learned

Imagine trying to make a ball-shaped robot that rolls in any direction but with a head that stays on. When I saw the BB-8 droid doing just that in the first Star Wars: The Force Awakens trailer, it was an interesting engineering challenge that I couldn’t resist. All the details for how I made it would fill a book, so here are the highlights: the problems I ran into, how I solved them and what I learned.

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Fashion Mannequin Is Fiberglass Reinforced Paper Craft

[Leah and Ailee] run their own handmade clothing business and needed a mannequin to drape their creations onto for display and photography. Since ready-made busts are quite pricey and also didn’t really suit their style, [Leah] set out to make her own mannequins by cleverly combining paper craft techniques and fiberglass.

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