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Maker Faire Prep: DIY multi-touch

IMG_6482 Today I've been preparing for my trip to the first UK Maker Faire in Newcastle in March. I'm taking some robots but also wanted to show something else. The interest in our multi-touch videos on YouTube has been encouraging. So I thought I'll make a more useable home brew multi-touch table.

So today, I've been busy filming and building. Everything we do these days has to produce content for many channels - video, in person, blogging etc etc - hence the filming. It has been fun - the filming is just like my own little production company. Location, scene and script planning all completed earlier in the week using PowerPoint - each slide being a new shot. PPT works very well like this :-)

But back to the building! I've constructed a simple table. The top has an acrylic sheet covering a diffusing material (grease proof paper at the moment - will get some Draughtman's paper tomorrow). Below the top is an LCD projector and a modified Xbox Live Vision camera.

IMG_6477 The camera has had its IR filter removed and replaced with a couple of pieces of exposed 35mm negative film. This enables the camera to see IR but reduces the amount of other light wavelengths that the camera can see. This is important as it is below the projection screen and would otherwise see the projector output on the screen. Modified it magically doesn't see any of the projected screen!

To calculate the distance between the projector and the screen I laid everything out horizontally on my lounge floor. I found that I needed the table leg height to be at least 90 cm. The projector doesn't fill my table top screen but it is a reasonable sized projection. I didn't want to have the device any taller as I plan to take the device to some school activities - the taller it is the less usable it is for younger children! Flexibility is the order of the day when trying this stuff out; so the camera is on length of wood held on by an elastic band, as are the 'legs' of angled metal holding the wood up right. The projector is on my mini-tripod. This extends beyond the size of the 'box' so I'll have to 'create' something else once I get close to final RC.

There are several techniques for multi-touch. The one I plan to use is called rear diffused illumination. This requires the projector and camera below the screen to be enclosed in a light tight box and then to have IR illumination on the underneath of the screen. I'm still waiting for my IR illumination devices to arrive so the testing so far, has all been done using ambient light from above - which works enough to provide encouragement! You can read more about the different multi-touch techniques at the excellent NUIGroup forum.

I plan to run the Multi-touch Vista application from Codeplex. This will allow me to build some demo applications with WPF (Windows Presentation Foundation). I'm hopefully, that I'll have enough time to port Dave Brown's physics application to the Touchable Panel - this apparently is eqv. to Surface's Scatterview control.

Once I get the video edited down I'll post that here too. I'm pretty pleased with my days' work!