Perceptibility of haptic digital watermarking of virtual textures

Digital watermarking refers to the process of embedding a digital code into an image, video, printed document or audio media. The code should not interfere with the normal use of the media but can be recovered later. With the growing interest in haptic interactions for training and museum displays, it is only a matter of time that haptic digital media become available on the Internet. For example, one will soon be able to feel the shape of Michaelangelo \´s David or Japan\´s Big Buddha by downloading a file that can be "played" on a force-feedback device. The haptic file may contain surface texture data in addition to topography so that David feels like marble and Big Buddha wood. In the meanwhile, the need for haptic digital watermarking will arise for protecting haptic media contents. This paper introduces for the first time the idea of haptic watermarking and shows one way to embed a watermark into a host surface texture signal. We also demonstrate the imperceptibility of the texture watermark in a psychophysical experiment.