Proceedings: GI 2011

2D similarity transformations on multi-touch surfaces

Behrooz Ashtiani , Wolfgang Stuerzlinger

Proceedings of Graphics Interface 2011: St. John’s, Newfoundland, Canada, 25 - 27 May 2011, 57-64

DOI 10.20380/GI2011.08

  • Bibtex

    author = {Ashtiani, Behrooz and Stuerzlinger, Wolfgang},
    title = {2D similarity transformations on multi-touch surfaces},
    booktitle = {Proceedings of Graphics Interface 2011},
    series = {GI 2011},
    year = {2011},
    issn = {0713-5424},
    isbn = {978-1-4503-0693-5},
    location = {St. John{\textquoteright}s, Newfoundland, Canada},
    pages = {57--64},
    numpages = {8},
    doi = {10.20380/GI2011.08},
    publisher = {Canadian Human-Computer Communications Society},
    address = {Toronto, Ontario, Canada},


We present and comparatively evaluate two new object transformation techniques for multi-touch surfaces. Specifying complete two-dimensional similarity transformations requires a minimum of four degrees of freedom: two for position, one for rotation, and another for scaling. Many existing techniques for object transformation are designed to function with traditional input devices such as mice, single-touch surfaces, or stylus pens. The challenge is to map controls appropriately for each of these devices. A few multi-touch techniques have been proposed in the past, but no comprehensive evaluation has been presented. XNT is a new three-finger object transformation technique, designed for multi-touch surfaces. It provides a natural interface for two-dimensional manipulation. XNT and several existing techniques were evaluated in a user study. The results show that XNT is superior for all tasks that involve scaling and competitive for tasks that involve only rotation and positioning.