Mar. 11, 2015 | By Alec

While 3D printing is in every way a futuristic technology that enables everyone to look forward, it’s always important to remember how long the road of scientific progress really is. That’s why its great to see that Providence, RI-based artist Kelly Egan has gone all the way back to the nineteenth century with his latest project: the Ponytrope, a 3D printed version of the classic zoetrope.

Now for those of you who don’t know what a zoetrope is, it is essentially one the first animation devices, popular before people even had access to electricity. ‘A zoetrope is a pre-cinematic animation technique where a series of animation frames are placed inside a spinning cylinder,’ Egan explains on his blog. The cylinder can be powered by hand and makes the frames move around too quick to see with the human eye. But when viewing them through slits in the drum, the frames of the animation become visible for a fraction of the second. When used with successive frames, the illusion of animation is created in your head.

As Egan explains, he wanted to remind audiences of that ancient technology with his entry for the World Makerfaire in New York. ‘The first time I saw the technique was Gregory Barsamian’s piece “Die Falle” (The Trap), at the Museum of Glass, in Tacoma, Washington. Seeing a three dimensional animation in person for the first time can be a bit unreal which is part of the reason I wanted to share it with the crowd at Makerfaire,’ he explains.

But to give it a modern edge, he decided to rely on 3D printing rather than on 2D paper frames to ‘animate'. ‘My 3D zoetrope relies on the same principles but instead of flat 2D frames I am using 3D models [of ponies] and instead of the slits I use a strobing LED light to illuminate each frame for a fraction of a second. The strobe and slits are necessary to freeze the frames, otherwise you would just see a blur.’ And as you can see in the images, it works quite well.

As he explains, these 3D printed ponies were designed in Blender, which has useful rigging options that enable users to easily give the different models natural poses. ‘This feature is great because if done correctly, you can move the armature and the form of the horse naturally follows.’ To make these look as natural as possible, Egan relied on the nineteenth century photos by Edweard Muybridge, a pioneer of high-speed photography and incidentally from the same period as the zoetrope itself.

Using a Python-based hack for Blender, these models were then converted to STL format (in two separate pieces) before sending them to his 3D printer. ‘Instead of printing the horse whole, I cut them in half to reduce the support structured needed to print. You can apply a boolean modifier to the base model in Blender and it applies to all the poses in the animation. I used another modifier to rotated the two halves so the cut side would lay flat on the print bed. Doing all this in Blender saved me a lot of cleanup work with the final print files,’ Egan explains.

In total, Egan’s PonyTrope consists of 12 3D printed horses, each in a different state of galloping. Connected to a central hub using basswood sticks, they are programmed to spin around through an Arduino. If you would like to recreate the PonyTrope, you can find the STL files on Egan’s Thingiverse page here and the code for the Arduino on his blog here.

But to ensure the LED creates the necessary animation effect, the trick is to get the speed of the motor just right. ‘There are twelve horses in the animation so the strobe should turn on once for each horse or twelve times per rotation. You can actually play with this a bit and get the horses to move backward or forward by increasing or decreasing the number of strobes per rotation slightly,’ Egan advises. ‘Once the speed is known the rate of the strobe can be set. While the time between strobes is variable I left the duration they are on at a constant one thousandth of a second. If the light is on for too long the horses will show some motion blur, just like if you use a slow shutter speed when taking a picture of something moving fast.’ Alternatively, that can be done by inserting an interrupt function, for which you’ll need to follow Egan’s guidelines closely.

But the result is worth the effort; when viewed in a dark room the effects are just spectacular. It really looks as if twelve tiny horses are running in circles in front of you, at least more realistically than many computer animations. It just goes to show that even the most futuristic technologies can learn from what preceded them.


Posted in 3D Printing Applications


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