Yeah. Umm… I’m an idiot. My dad and I drilled holes in the aluminum frame. I did not heed the advice that we needed to cut the metal at a 45 degree angle, so now the ends of the aluminium butt up against each other, causing a half inch or so of aluminum to stick off of the acrylic, and a small half inch square of bare acrylic on the sides.
I may be able to make it work afterall, but chances are I’ll be going to Home Depot and picking up some more aluminium.
We all learn from our mistakes, and I guess I got lucky in the fact this one cost me only $19 or so.
I saw this video on Mike Wags’ blog a few days ago. Out of the few I’ve seen on YouTube, this is probably the clearest video of the reactable live. (Besides the demo videos of course!)
Björk is the first musician to use a reactable in concert, and will be doing so for the next 18 months on her Volta world tour.
If you don’t know what a reactable is, I’ll explain. It is similar to a FTIR multitouch display, except that it uses the diffused illumination method (Light shines through the back of a glass/acrylic panel and lights up the surface of the glass or acrylic. Microsoft’s Surface uses this method.) This method allows for detection of shapes and some images(in the case of the reactable, fiducials - blocks with a special geometrical design printed on the bottom of them). The reacTIVision software detects unique fiducial designs and then feeds this data into a program that matches a musical instrument or synthesizer to each tangible (the blocks with the fiducials on them). Twisting or moving the tangible on the table changes the sound of the synth, and you can use multiple tangibles together. The current reacTIVision software allows for finger tracking, but you have to put a special finger marker on your fingertips. From what I’ve heard, the next verison of reacTIVision, reacTIVision 1.4, will include blob tracking.
When I first started this blog, I stated in my first post that I was working on a guide on how to install OpenCV on a Mac. Well, it has been over two months since I said that. I did finish the guide, and I posted on the NUI Group forums over two months ago in this thread. I also posted it in the NUI Group Wiki here so that if anyone finds in errors in the guide they can edit it and add their corrections.
I plan on rewriting it one day and creating a very nice, better organized, PDF verison.
My piece of acrylic arrived yesterday; a week in advance of when I expected it. Now I have to go buy the rest of the sandpaper (I already have 800, 1000, 2000 grit). I plan on sanding the edges of the panel with 100, 200, 400, 600, 800, 1000, 1500, and 2000 grit, then polish them with brass or silver polish for completely clear edges.
The sheer size of the acrylic panel has brought up several concerns. I have realized that a simple table setup will be to big to fit through most of the doors in my house
I will probably be building a vertical, wall type frame for the acrylic, like Mike Wags has done.
My silicone rubber sheet, LEDs, resistors, and clips arrived yesterday. I ordered some battery connector clips to save from soldering hundreds of connections. Just slide the LED pins in the holes, and you gain a 7.5 inch long wire. The silicone rubber sheet from Harry turned out pretty nicely. I tested the LEDs on a 1/14th scale and the PC power supply worked great.
Arggghhh. The acrylic came a week ahead of schedule yesterday. But someone at the glass company thought it would be smart to try to pass off a 36 by 25 inch sheet for a 36 by 28 inch sheet. Of course, for nearly $130, I am sending this sheet back. Unfortunately it will take 3 weeks to get the new sheet in. So the total “2 week wait” has become 4-5 weeks. Great.
I ordered my compliant surface late last night. I chose a silicone rubber sheet from Harry van der Veen because it seems like it works the best so far. I will have a 32 inch by 24 inch by 0.5mm thick silicone rubber sheet coming in the next few days or weeks (depending on how the Swedish mail service handles it).
A compliant surface is a layer of material on top of the acrylic that helps create better blobs, generally by bringing the light closer to your finger.
Normally, you have to press down with a good bit of force to get your touch to register with bare acrylic. This is because when you set your finger onto the surface of the acrylic, some of the IR light hits the ridges on your finger and becomes diffused, making a blob. But you still have the recessed areas on the surface of your finger where the light doesn’t hit and diffuse.
With a compliant surface, like a silicone rubber sheet, the light can get to all parts of your finger. This is because when you place your finger on the silicone rubber, it always - even though very slightly - presses into the silicone, making a very small indention. Because the IR light terminates on the flat surface of the silicone, when you make the curved indention into the sheet it brings your finger closer to the IR light than with bare acrylic, which does not bend inward at all.
I hope you can kind of get an idea of what I’m talking about. Maybe when I finally start collecting all the parts and building my display it will be easier to show you guys.
I have just ordered my acrylic (plexiglas) sheet. I have decided on a 32 inch by 24 inch multitouch display, giving me a 40 inch diagonal display.
I ordered the sheet leaving 2 inches on each side for mounting.
I guess I got a good deal on it; $127.22 shipped for a 36 by 28 by 0.5 inch sheet.
It’s still kind of pricey because I’m trying to keep this project under $1000 with the projector. I’m thinking of getting the Mitsubishi PK-20 LED projector, but because it uses a high power LED instead of a 180 Watt HID bulb, it is only about 25 lumens. Compare that to 1600-2000 lumens for a standard projector. The main advantage of an LED projector is that the LED never needs to be replaced, unlike normal projector lamps that blow after about 2000 hours, sometimes even less. The PK-20’s LED is rated at 10,000 hours.
It’s also very, very small at only 3.82 by 4.84 by 1.90 inches. This thing is half as tall as a soda can. Mitsubishi actually makes a 2 hour battery pack for this little projector. Another advantage of an LED projector is that there is nearly no IR light put out.
I have narrowed my choice of projectors to the Mitsubishi PK-20 and the Epson PowerLite S4. The PK-20 is $500, and the PowerLite S4 is $590 from Newegg. But, the PowerLite S4 replacement lamps are $200. According to Epson, at full brightness the lamp needs to be replaced every 2000 hours. I like to be conservative on things like that, so I would only expect 1500 hours at full brightness.
Microsoft has announced a multitouch table called Surface. It doesn’t look like there is much innovation. Most of the things they showed Surface doing has already been done by Jeff Han and the multitouch community. The one interesting and new thing (at least that I haven’t seen done) is the ability to sync and transfer files from multiple wireless devices set on the screen. Interesting, but so far it’s all I’ve seen that’s new.
