A 3D Scanner that Archimedes Could Get Behind

3D-scanning seems like a straightforward process — put the subject inside a motion control gantry, bounce light off the surface, measure the reflections, and do some math to reconstruct the shape in three dimensions. But traditional 3D-scanning isn’t good for subjects with complex topologies and lots of nooks and crannies that light can’t get to. Which is why volumetric 3D-scanning could become an important tool someday.

As the name implies, volumetric scanning relies on measuring the change in volume of a medium as an object is moved through it. In the case of [Kfir Aberman] and [Oren Katzir]’s “dip scanning” method, the medium is a tank of water whose level is measured to a high precision with a float sensor. The object to be scanned is dipped slowly into the water by a robot as data is gathered. The robot removes the object, changes the orientation, and dips again. Dipping is repeated until enough data has been collected to run through a transformation algorithm that can reconstruct the shape of the object. Anywhere the water can reach can be scanned, and the video below shows how good the results can be with enough data. Full details are available in the PDF of their paper.

While optical 3D-scanning with the standard turntable and laser configuration will probably be around for a while, dip scanning seems like a powerful method for getting topological data using really simple equipment.

Thanks to [bmsleight] for the tip.

All Your Displays Are Belong to Us

Artist and Hackaday reader [Blair Neal] wrote in with his incredible compendium of “alternative” displays. (Here as PDF.) From Pepper’s Ghost to POV, he’s got it all covered, with emphasis on their uses in art.

There’s an especially large focus on 3D displays. Projecting onto screens, droplets of water, spinning objects, and even plasma combustion are covered. But so are the funny physical displays: flip-dots, pin-cushions, and even servo-driven “pixels”.

Flavien Théry’s La Porte 
Flavien Théry’s La Porte

We really liked the section on LCDs with modified polarization layers — we’ve seen some cool hacks using that gimmick, but the art pieces he dredged up look even better. Makes us want to take a second look at that busted LCD screen in the basement.

We’re big fans of the bright and blinky, so it’s no surprise that [Blair] got a bunch of his examples from these very pages. And we’ve covered [Blair]’s work as well: both his Wobbulator and his “Color a Sound” projects. Hackaday: your one-stop-shop for freaky pixels.

[Blair]’s list looks pretty complete to us, but there’s always more out there. What oddball displays are missing? What’s the strangest or coolest display you’ve ever seen?

How a Real 3D Display Works

There’s a new display technique that’s making the blog rounds, and like anything that seems like its torn from [George Lucas]’ cutting room floor, it’s getting a lot of attention. It’s a device that can display voxels in midair, forming low-resolution three-dimensional patterns without any screen, any fog machine, or any reflective medium. It’s really the closest thing to the projectors in a holodeck we’ve seen yet, leading a few people to ask how it’s done.

This isn’t the first time we’ve seen something like this. A few years ago. a similar 3D display technology was demonstrated that used a green laser to display tens of thousands of voxels in a display medium. The same company used this technology to draw white voxels in air, without a smoke machine or anything else for the laser beam to reflect off of. We couldn’t grasp how this worked at the time, but with a little bit of research we can find the relevant documentation.

A system like this was first published in 2006, built upon earlier work that only displayed pixels on a 2D plane. The device worked by taking an infrared Nd:YAG laser, and focusing the beam to an extremely small point. At that point, the atmosphere heats up enough to turn into plasma and turns into a bright, if temporary, point of light. With the laser pulsing several hundred times a second, a picture can be built up with these small plasma bursts.


Moving a ball of plasma around in 2D space is rather easy; all you need are a few mirrors. To get a third dimension to projected 3D images, a lens mounted on a linear rail moves back and forth changing the focal length of the optics setup. It’s an extremely impressive optical setup, but simple enough to get the jist of.

Having a device that projects images with balls of plasma leads to another question: how safe is this thing? There’s no mention of how powerful the laser used in this device is, but in every picture of this projector, people are wearing goggles. In the videos – one is available below – there is something that is obviously missing once you notice it: sound. This projector is creating tiny balls of expanding air hundreds of times per second. We don’t know what it sounds like – or if you can hear it at all – but a constant buzz would limit its application as an advertising medium.

As with any state-of-the-art project where we kinda know how it works, there’s a good chance someone with experience in optics could put something like this together. A normal green laser pointer in a water medium would be much safer than an IR YAG laser, but other than that the door is wide open for a replication of this project.

Thanks [Sean] for sending this in.

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3D display controlled with the Leap Motion


Touch screens are nice — we still can’t live without a keyboard but they suffice when on the go. But it is becoming obvious that the end goal with user interface techniques is to completely remove the need to touch a piece of hardware in order to interact with it. One avenue for this goal is the use of voice commands via software like Siri, but another is the use of 3D processing hardware like Kinect or Leap Motion. This project uses the latter to control the image shown on the 3D display.

[Robbie Tilton] generated a 3D image using Three.js, a JavaScript 3D library. The images are made to appear as if floating in air using a pyramid of acrylic which reflects the light toward the viewer’s eyes without blocking out ambient light in the room. In the past we’ve referred to this as a volumetric display. But [Robbie] points out that this actually uses the illusion called Pepper’s Ghost. It’s not really volumetric because the depth is merely an illusion. Moving your point of view won’t change your perspective unless you go around the corner to the next piece of acrylic. But it’s still a nice effect. See for yourself in the demo after the jump.

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Volumetric display looks like a DaVinci sketch

This volumetric display really shows a lot of potential. And it has just the right balance of simplicity and ingenuity. The rig is being developed by [Michel David] and involves a screen shaped like a helix, and a laser which shines through an optical filter disk.

The moving parts of the device are mounted on the same shaft, which is spun by a belt system connected to a Dremel tool. Since the screen and the information disc are mounted on the same shaft, one part of the synchronization process is already taken care of. You can see the separate stand for the projector, which is a laser in this case but is designed to work with other light sources as well. Since the projection surface is moving towards and away from the projector, a laser is preferrable because of focus issues. Unfortunately [Michel] has been having some issues with switching the diode at high enough frequencies. Still, we think the results in the clip after the break are marvelous.

As far as hardware is concerned, this is a lot simpler than trying to spin a large LED matrix.

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Building a multidimensional display from trash

Here’s a simple concept that will let you turn any LCD screen into a multidimensional display (translated). [Herdek] used bits of that impossible to open clear plastic packaging to construct this add-on for the smart phone seen above. Three pieces of the material have been mounted at a 45 degree angle between the screen and viewer. The material is both reflective and transparent, depending on the angle at which light hits it. This allows it to reflect the light from the screen toward the viewer, but let light from the baffles behind it pass through unimpeded. The three baffles allow the LCD to be partitioned into three different sections whose images will appear to be at different depths according to the viewer’s vantage point. After the break we’ve embedded a demonstration video, as well as the how-to that shows the construction technique for the add-on.

This follows the same concept at the pyramidal volumetric display, which is still one of our favorite LCD hacks.

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Glimpses of a 3D volumetric display

Custom displays are a lot of fun to look at, but this one is something we’d expect to see at a trade show and not on someone’s kitchen table. [Taha Bintahir] built a 3D volumetric display and is showing it off in the image above using a 3DS file of the Superman logo exported from Autodesk. In the video after the break you can see that the display is a transparent pyramid which allows a viewer to see the 3D object inside from any viewpoint around the display. Since first posting about it he has also added a Kinect to the mix, allowing a user to control the 3D object with body movements.

There’s basically no information about the display hardware on [Taha’s] post so we asked him about it. It works by first taking a 3D model and rendering it from four different camera angles. He’s using a custom designed prism for he display and the initial renderings are distorted to match that prism’s dimension. Those renderings are projected on the prism to give the illusion of a 3D object floating at its center.

We’re hoping to hear more details about how this was designed and what hardware is being used. We’ll post a follow-up if [Taha] shares more information.

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