ABSTRACT
The goal of haptic rendering is to enable a user to touch, feel, and manipulate virtual objects through a haptic interface. With the introduction of high-fidelity haptic devices (see chap. 5, this volume), it is now possible to simulate the feel of even fine surface textures on rigid complex shapes under dynamic conditions. Starting from the early 1990s, significant progress has occurred in our ability to model and simulate haptic interactions with three-dimensional (3-D) virtual objects in real time (Salisbury & Srinivasan, 1997; Srinivasan & Basdogan, 1997). The rapid increase in the number of workshops, conference sessions, community web pages, and electronic journals on haptic displays and rendering techniques∗ indicates growing interest in this exciting new area of research called computer haptics. Just as computer graphics is concerned with synthesizing and rendering visual images, computer haptics is the art and science of developing software algorithms that synthesize computer generated forces to be displayed to the user for perception and manipulation of virtual objects through touch. Various applications of computer haptics have been developed in the areas of medicine (e.g., surgical simulation, telemedicine, haptic user interfaces for blind people, rehabilitation of patients with neurological disorders; see chaps. 47-51, this volume), entertainment
(e.g., 3-D painting, character animation, morphing and sculpting; see chap. 55, this volume), mechanical design (e.g., path planning and assembly sequencing; see chap. 54, this volume), and scientific visualization (e.g., geophysical data analysis, molecular manipulation; see chap. 53, this volume). More applications are anticipated as devices and rendering techniques improve and computational power increases. This chapter will primarily focus on fundamental concepts of haptic rendering, with some discussion of implementation details. Although, it is impossible to cite all relevant work within the constraints of this chapter, an attempt has been made to cover the major references. Given that current technology is mature for net force and torque feedback (as in tool usage in the real world) and not tactile feedback (as in actual distribution of force fields on the skin during contact with real objects), the discussion is restricted to techniques concerning the former. In general, the concepts discussed in the chapter include: (1) haptic interaction paradigms, which define the nature of the “haptic cursor” and its interaction with virtual objects; and (2) object property display algorithms, which enable rendering of surface and material properties of objects and their behavior through repeated use of the haptic interaction paradigm.
