One of the most powerful results of recent advances in graphics hardware is the ability of a computer user to interactively explore a virtual building or landscape. The newest three-dimensional input devices, together with high speed 3D graphics workstatio

11

Interactive Scene Walkthrough Using aPhysically-Based Virtual Camera

Russell Turner, Jean-Francis Balaguer, Enrico Gobbetti,Daniel Thalmann

Laboratoire d'Infographie

EPF Lausanne

CH 1015 Lausanne, Switzerland

One of the most powerful results of recent advances in graphics hardware is the ability of a computeruser to interactively explore a virtual building or landscape. The newest three-dimensional inputdevices, together with high speed 3D graphics workstations, make it possible to view and move througha 3D scene by interactively controlling the motion of a virtual camera. In this paper, we describe hownatural and intuitive control of building walkthrough can be achieved by using a physically-basedmodel of the virtual camera's behavior. Using the laws of classical mechanics to create an abstractphysical model of the camera, we then simulate the virtual camera motion in real time in response toforce data from the various 3D input devices (e.g. the Spaceball and Polhemus 3Space Digitizer). Theresulting interactive behavior of the model is determined by several physical parameters such as mass,moment of inertia, and various friction coefficients which can all be varied interactively, and byconstraints on the camera's degrees of freedom. This allows us to explore a continuous range ofphysically-based metaphors for controlling the camera motion. We present the results of experimentsusing several of these metaphors for virtual camera motion and describe the effects of the variousphysical parameters.

Introduction

With the existence of graphics workstations able to display complex scenes containing severalthousands of polygons at interactive speed, and with the advent of such new multiple degree-of-freedom interactive devices as the Spaceball, Polhemus 3Space, and DataGlove, it is now possibleto create graphics applications based on a full 3D interaction metaphor in which the specification ofthe camera motion is given in real-time.

Interactive virtual camera motion is an important technique in a number of different computergraphics areas: animation, scientific visualization, CAD and virtual environment applications allmake considerable use of interactive virtual camera control in a three-dimensional environment togive the user the possibility of moving inside computer-generated virtual scenes (Baum et al. 1990,Magnenat-Thalmann and Thalmann 1986, Shinagawa et al. 1990). In architectural CADapplications, this gives both the architect and the client the ability to walk through virtual buildings