Multi-Touch Terminology

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  • Multi-touch – An interactive technique that allows single or multiple users to control graphical displays with more than one simultaneous finger.
  • Multi-point – An interactive technique that makes use of points of contact rather than movement. A multi-point kiosk with buttons would be an example.
  • Multi-user – A multi-touch device that accepts more than one user. Larger multi-touch devices are said to be inherently multi-user.
  • Multi-modal – A form of interaction using multiple modes of interfacing with a system.
  • Tabletop Computing – Interactive computer displays that take place in the form of tabletops.
  • Direct Manipulation – The ability to use the body itself (hands, fingers, etc) to directly manage digital workspaces.
  • Blob tracking - Assigning each blob an ID (identifier). Each frame we try to determine which blob is which by comparing each with the previous frame.
  • Blob detection - Process of picking out bright areas of a camera image and somehow relaying them to a computer as a touch.


  • Blob - A bright luminescent object
  • Blob detection' - refers to visual modules that are aimed at detecting points and/or regions in the image that are either brighter or darker than the surrounding.
  • False Blob - A blob that is being reported by the tracker, but does not represent an actual object on the surface
  • Nice Blobs - Blobs with a lot of contrast to the background image. These are Nice Blobs:


  • Tracker - The program which takes images from a camera, puts them through several filters, and finally reports the position, size, and relative movement of blobs over some protocol
  • TUIO - A protocol used for communicating the position, size, and relative velocity of blobs. It is built on OSC, which is built on UDP
  • Touch Event – A term used to describe when a system knows that an object has touched the multi-touch device.
  • Gesture – A physical movement that can be sensed, and often an action assigned to it. Some common gestures are single finger panning, and two finger zoom-pinching
  • Sensor – A device that measures changes in an environment. sensors list
  • Open Sound Control (OSC) – A network communication protocol built on UDP

Open Sound Control (OSC) is an open, transport-independent, message-based protocol developed for communication among computers, sound synthesizers, and other multimedia devices.

  • Tangible User Interface Objects (TUIO) [8] – A protocol and standard way of sending OSC messages for tabletop displays. TUIO is sometimes used by *open-source communities as the communication layer between server and client.
  • Zoomable User Interface (ZUI) – A user interface in which the entire thing is zoomable. In theory this would give you infinite workspace, but memory constrictions limit this
  • Touchlib [2] – A widely used open-source tracking and event library for optical based infrared multi-touch solutions. This is an example of a Tracker


  • Diffuser – Something that spreads and scatters light. A diffuser is used in various multi-touch techniques to create even lighting.
  • Frustrated Total Internal Reflection (FTIR) – A multi-touch technique that exploits the phenomena of Total Internal Reflection(TIR) [2]. Light within a transparent channel of low refractive index will reflect internally until an object with a higher refractiveindex, such as a finger, touches or frustrates the surface thus lighting up the frustrated area.
  • Diffused Illumination (DI) – A multi-touch technique that makes use of a diffused surface to help filter shadows (Front DI) orilluminated fingers (Rear DI) from a touch surface. Sometimes this is referred to as Direct Illumination
  • Laser Light Plane (LLP) – A multi-touch technique that uses a laser and line generating lens to cast a beam over a touch surface.When the beam plane is broken by an object, the area is lit up.
  • Diffused Surface Illumination (DSI) – A multi-touch technique that uses a special acrylic Endlighten to help disperse even light supplied by edge lighting the acrylic. The effect is similar to DI.
  • Stereo Vision or Stereoscopic – A two camera multi-touch technique.
  • Zero Force – Refers to the amount of force or pressure needed to trigger a touch event. In this case, 'zero' means 'little.'

General Software

  • Touchlib – A widely used open-source tracking and eventlibrary for optical based infrared multi-touch solutions. This is an example of a Tracker
  • reacTIVision - A fiducial-based, open-source tracker.

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