Multitouch

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Multi Touch Introduction

What is multi touch?

Multi-touch (or multitouch) denotes a set of interaction techniques which allow computer or mobile users to control graphical user interface with more than one finger at either application or system level. The term Multi-Touch is a trademark of Apple, Inc. Apple Trademark List[1]

Multi-touch consists of a touch screen (screen, overlay, table, wall, etc.) or touchpad, as well as software that recognizes multiple simultaneous touch points, as opposed to the single touchscreen (e.g. computer touchpad, ATM), which recognizes only one touch point. This effect is achieved through a variety of means, including: heat, finger pressure, high capture rate cameras, infrared light, optic capture, tuned electromagnetic induction, ultrasonic receivers,a transducer microphones, laser rangefinders, and shadow capture.

Many products using multi-touch interfaces exist and are being developed. Multi-touch is used on portable devices including the Apple Inc iPhone, HTC Hero, Microsoft's Zune HD, Samsung Memory, and the Palm Pre, as well as desktop products such as the Microsoft Surface and the DELL Latitude XT2

DIY multi touch

Hobbyists have developed extremely low cost touchscreen technologies using webcams, projection of image, and software that senses touch patterns via the webcam. Multi touch screens larger than 50" are possible at costs under $100 to $400 depending on the projector & equipment used. DIY multitouch screens of extremely large size (wall sized or larger) are also quite possible and very cheaply constructed and posted in numerous places on the web.

Software to make it work

All of the projects depend on some software to make all the components work with your pc.

WIImote connection

Some projects depend on a WII remote to connect it to your pc and get it working:

1. Get your pc to communicate with your WIImote, there are loads of guides out there, but most of the time it is just straight forward like connecting any other BlueTooth device. 2. Install the software that will track the infrared dots: http://johnnylee.net/projects/wii/WiimoteWhiteboardv03.zip 3. have fun!

Different ways of DIY multi touch

I will explain some ways to make a multi touch device.

Webcam, plastic cardboard box and some tracing paper

Short explanation

This is a very easy way of making a multi touch input device which is very effective and accurate. The downside of this project is that you have to control on 1 screen and look what you are doing on the other screen this can make coördination difficult, this doesn't matter though for some applications like drawing.

What do you need?

  • Sheet of hard plastic
  • Cardboard box (the same size as your plastic)
  • Webcam (or WIImote, see NOTE)
  • Software (free, open source software that is of course)

How to Build

Take the webcam and tape it to the bottom of the cardboard box. Make a hole in the side of the box, so that the usb-cable can still go to your computer while the webcam is inside the box. Next take some tape to make the inside of the box dark and only let the top open. On this open top put a sheet of hard-plastic. Tape the plastic to the box and put a sheet of tracing paper on top and yes that's all you're done.

Note

This project might also be possible with the use of an WIImote, although i haven't tested it there is the same technology in a WIImote as there is in a webcam the only problem might be that the infrared blips might be to weak to wreckonise for the WIImote.

Digital Whiteboard (WIImote)

What do you need?

  • WIImote
  • Beamer
  • Something to mount the WIImote on
  • Projection screen / wall to project on
  • infrared LED Pen(s) (these can be bought at: WEBSITE LED)

Short explanation

This is one of the most expensive multi-touch projects as you really need a beamer (for a project without beamer see the NOTE section). But really this is a very fun thing to build and can also be a very easy project which can be the base for a lot of other projects and some really practical things you can do with it. The idea is to make the WIImote track your infrared LED's after a 4-point calibration of your screen and thus making the entire surface you want (multi)touchable.

How to build

Set up your WIImote somewhere in front of the thing you are going to project on, with all of the corners visible to the WIImote (the viewing angle is about 45* horizontal and vertical) and in a way you won't be in the line between your LED pen(s) and the WIImote. You might want to test a bit with this as it is the best for your touching resolution to get the corners of your projection area just inside the corners of the WIImote reach. After start up the software mentioned earlier in the SOFTWARE section and after a short 4 point calibration you are ready to control your pc with your pen(s). Multitouch is not available for windows and is only available within multitouch applications. See the SOFTWARE section for more info.

Note

This project can also be done with multiple WII motes to make sure you are never in front of the viewing capabilities of your WIImote. The program suggested in the SOFTWARE section is capable of supporting multiple WIImotes.

Demonstration movie

http://www.youtube.com/watch?v=5s5EvhHy7eQ&feature=channel

Colored dye in a plastic bag

What do you need?

  • Glass table (or any other clear see-through material table)
  • Plastic (watertight) bag
  • Some dye (can be bought at any hobby/(art)paint shop
  • Webcam

Short explanation

The dye in the bag reflects the light in a certain way, if you touch the bag in a certain place the light will be directed differently and this difference can be measured by the webcam under the bag.

Demonstration movie

http://www.youtube.com/v/yzNh31q61gc