The Race Is On To Build A Raspi Kinect 3D Scanner

pinect

The old gen 1 Kinect has seen a fair bit of use in the field of making 3D scans out of real world scenes. Now that Xbox 360 Kinects are winding up at yard sales and your local Goodwill, you might even have a chance to pick one up for pocket change. Until now, though, scanning objects in 3D has only been practical in a studio or workshop setting; for a mobile, portable scanner, you’d need to lug around a computer, a power supply, and it’s not really something you can fit in a back pack.

Now, finally, that may be changing. [xxorde] can now get depth data from a Kinect sensor with a Raspberry Pi. And with just about every other ARM board out there as well. It’s a kernel driver that’s small, fast, and does just one thing: turns the Kinect into a webcam that displays depth data.

Of course, a portabalized Kinect 3D scanner has been done before, but that was with an absurdly expensive Gumstix board. With a Raspi or BeagleBone Black, this driver has the beginnings of a very cheap 3D scanner that would be much more useful than the current commercial or DIY desktop scanners.

Copying objects in 3D

photocopier

[Pulse 9] sent in a very interesting project he just finished up at an internship. It’s a 3D photocopier that scans an object and then mills said object into floral foam.

The copier is made out of material [Pulse] found sitting around – PVC, drawer slides for the X and Y axes, acrylic for the structure, and broken printer parts for the Z axis.

To scan an object, [Pulse] puts an object down on the bed and scans it with a laser and webcam. The images recorded on the camera are fed into MATLAB. The output from MATLAB is sent over serial to a custom board containing a PIC18F4620 that controls the axis motors. The spindle for this floral foam router is a simple drill; one layer at a time, the drill mills out the unneeded foam which can be sucked up by a vacuum when the object is complete.

Below you’ll find [Pulse]‘s demo of his photocopier and a piece the local news did on the project. If anyone is willing to translate that story, feel free to do so in the comments.

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TightLight: A 3D projection mapping assistant

tightLight

Anyone can grab a projector, plug it in, and fire a movie at the wall. If, however, you want to add some depth to your work–both metaphorical and physical–you’d better start projection mapping. Intricate surfaces like these slabs of styrofoam are excellent candidates for a stunning display, but not without introducing additional complexity to your setup. [Grady] hopes to alleviate some tedium with the TightLight (Warning: “music”).

The video shows the entire mapping process of which the Arduino plays a specific role toward the end. Before tackling any projector calibration, [Grady] needs an accurate 3D model of the projection surface, and boy does it look complicated. Good thing he has a NextEngine 3D laser scanner, which you’ll see lighting the surface red as it cruises along.

Enter the TightLight: essentially 20 CdS photocells hooked up to a Duemilanove, each of which is placed at a previously-marked point on the 3D surface. A quick calibration scan scrolls light from the projector across the X then Y axis, hitting each sensor to determine its exact position. [Grady] then merges the photocell location data with the earlier 3D model using the TouchDesigner platform, and bam: everything lines up and plays nice.

Complex camera rig controlled with Blender 3D

blender-3d-camera-control

This is a pretty intricate camera mount. Not only does it provide pan and tilt as the subtitles state, but it moves along a track and offers zoom and focus controls. Its great, but you’ll need an equally complex set of controls to do anything meaningful with it. That’s where the real hack comes into play. The entire system is controlled by its virtual model in Blender 3D.

You probably already know that Blender 3D is an open source 3-dimensional modeling suite. It’s got a mountain of features, which include a framework for animating virtual objects. The camera rig was replicated inside of the software, and includes a skeleton that moves just like the real thing. You can make an animation of how the camera should move, then export and play back those motions on the physical hardware.

Now if you need help making 3D models of your hardware perhaps you should try scanning them.

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3D scanner with remarkable resolution

diy-3d-scanner

Modeling simple objects in 3D can take some time. Modeling complex items… well you can get your college degree in that sort of thing. This method side-steps the artistic skill necessary to make the real virtual by using a laser and camera to map a three-dimensional object.

[Alessandro Grossi] is breaking the rules by using a 100mW laser for the project. He thinks that the Italian government prohibits anything over 5mW, but also mentions that the lens used to turn the laser dot into a vertical line drops the power dramatically. The beefy diode does still pay off, providing an incredibly intense line of light on the subject being mapped. The high-end DSLR camera mounted on the same arm as the laser captures a detailed image, which can be processed to dump everything other than the laser line itself. Because the two are mounted on different axes, the image provides plenty of perspective.  That translates to the 3D coordinates used in the captured model shown in the inlaid image.

We’ve seen 3D scanners that move the subject; they usually rotate it to map every side. This method only captures one side, but the stepper motor moves in such small increments that the final resolution is astounding. See for yourself in the video after the break.

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3D display controlled with the Leap Motion

3d-display-controlled-with-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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Turning 3D shutter glasses into automatic sunglasses

[Dino's] hack this week seeks to create sunglasses that dim based on the intensity of ambient light. The thought is that this should give you the best light level even with changing brightness like when the sun goes behind a cloud or walking from inside to outside. He started with a pair of 3D shutter glasses. These have lenses that are each a liquid crystal pane. The glasses monitor an IR signal coming from a 3D TV, then alternately black out the lenses so that each eye is seeing a different frame of video to create the stereoscopic effect. In the video after the break he tears down the hardware and builds it back up with his own ambient light sensor circuit.

It only takes 6V to immediately darken one of the LCD panes. The interesting thing is that it takes a few seconds for them to become clear again. It turns out you need to bleed off the voltage in the pane using a resistor in order to have a fast response in both directions. Above you can see the light dependent resistor in the bridge of the frame that is used to trigger the panes. [Dino] shows at the end of his video that they work. But the main protective feature of sunglasses is that they filter out UV rays and he’s not sure if these have any ability to do that or not.

[Read more...]

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