IResearch Notes Representation of Simple Graphs in Virtual Tactile Space Harry J. Wyatt, Elaine C. Hall, and Kimberly Engber One mode by which graphic-spatial information may be presented to persons who are blind is through touch. Such repre- sentations range from embossed drawings (see, for example, Horsfall, 1997; "HumanWare Braille Solutions," 2000; "ViewPlus Technologies Today," 2000; "Welcome to TAEVIS," 2000) to three- dimensional dynamic displays (see, for example, "Haptics," 1998). The authors have developed and con- ducted a preliminary evaluation of an inter- mediate form of presentation that provides a virtual dynamic tactile display. Such a device could be a standard addition to com- puters for people who are blind, in the form of an augmented mouse. It could provide real-time display of information to students of geometry, professionals in technical fields, persons examining financial charts, and so forth. METHODS AND RESULTS Hardware Two refreshable braille cells were obtained from F. J. Tieman (in Rockanje, Holland) and its affiliated company The authors are grateful to Koen Weijand, C. A. van Strien, and Ronald Roeten, of Tieman, and to Jim Halliday, of HumanWare, for providing the braille cells and related technical information. John Orzuchowski, State College of Optometry, State University of New York, provided extensive help in developing the electronics and interfacing. Accepted October 19, 1999. HumanWare (in Loomis, California). Placed side by side, the cells form an array of 4 x 4 pins that are used as a tactile dis- play for one finger. (Interpin spacing: approximately 2.5 mm, except 4.0 mm between neighboring pins of the adjacent cells. Overall dimensions of the array: approximately 7.5 mm x 9 mm.) By bypassing the serial decoding mechanisms on the cells, it was possible to activate the pins directly using signals from a PC inter- face card. The two cells were attached to the side of a computer mouse, as shown in Figure 1. Programming was carried out in ASYST (by Keithley/Metrabyte, Cleveland, Ohio). This general-purpose mathematical and laboratory software (Hary, Oshio, & Flana- gan, 1987) operates in the DOS environ- ment (or with some success in a DOS window), but is "orphan" software (no longer supported and not designed for a Windows environment). For test purposes, three types of lines were used: straight lines, circles, and data records from (unrelated) experiments mon- itoring eye position. The last type consists of 200-1,000 sequential values, equally spaced in time; any time series of measure- ments would suffice. The data were smoothed. Program logic The location and form of the lines were held in computer memory. The position of the mouse was continuously updated, and the positions of the pins were calculated. If a pin was within some criterion distance of a line, it was pushed out, as shown in Figure 2. Thus, as the mouse moves across the position of a "line," appropriate pins are pushed out, giving the sensation of moving ©2000 AFB, All Rights Reserved Journal a/Visual Impairment & Blindness, November 2000 713