Abstract

Evidence from the archaeological record yields clues as to how our ancestors lived. However, our perceptions and analyses of this data may be clouded by the lack of surviving structures or unmodified landscapes that can be used to put this evidence into a better context. Recent developments in computer visualization are providing powerful tools for modelling multi-dimensional aspects of the data gathered by archaeologists. Computer graphic techniques can be used to reconstruct and visualize features of a site which may otherwise be difficult to appreciate. This new perspective may enhance our understanding of the environments in which our ancestors lived. Recent developments have made it possible to 'construct' virtual environments on a computer and view photo-realistic images of these scenes [4]. It is possible, therefore, to recreate an archaeological site on a computer and provide the viewer with an accurate representation of the actual rernains. Furthermore, geometric modelling techniques enable extrapolations from existing evidence to reconstruct the site as it may have appeared to the original inhabitants [5]. Although static images are useful for providing impressions of a site, far greater insight can be obtained by making it possible for the user to navigate through the three dimensional representation. This experience will be enhanced by the photo-realistic nature of the computer model including accurate illumination and the presence of environmental factors such as smoke dust or fog. It is essential that such a navigation systern is interactive, responding immediately to the operator's directions [3]. In all image synthesis techniques, the fundamental step is computing the amount and nature of light from the three dimensional environment reaching the eye from any given direction. This computation is carried out by simulating the behaviour of light in the environment. This simulation must allow for the medium participation of light emitters such as flames, light absorbers such as soot clouds, and light scatterers such as dust or smoke. The particle tracing technique traces the path of photons as they are emitted from light sources and uses the reflected/refracted/emitted particle flux given by a large number of these particles as a measure of the illumination of the environment [4]. This model accurately simulates the physical propagation of light, and can be used for complex scenes involving medium participation. Experience, based on sequential implementations of the particle tracing method, has shown that even for relatively simple environments the number of particles that have to be considered in the simulation can be of the order of a few hundred thousand. On the single processor machine this can amount to many minutes and even hours of computing time. The application of advanced parallel processing methods should allow the visualization to be accomplished in real-time [1,2].This paper will describe a parallel computer system, currently under development as a joint project between computer scientists and archaeologists, for reconstructing and photo-realistically visualizing archaeological sites.References:[1] A. G. Chalmers, S. Pattanaik, A. Biriukov, and P. Sharpe. Parallel processing for interactive photo-realistic building walkthroughs. In W. Straser and F. Wahl, editors, Graphics & Robotics, Schloss Dagsthul, Apr. 1993.[2] F. W. Jansen and A. G. Chalmers. Realism in real-time? In Proceedings of the Fourth Eurographics Workshop on Rendering, Paris, June 1993.[3] J.H.R. John, M. Airey and F.P.Brooks Jr. Towards image realism with interactive update rates in complex virtual building enviromnents. ACM SIGGRAPH Special Issue on Interactive 3D graphics, 24(2):41-50,1990.[4] S.N. Pattanaik. Computational methods for global illumination and visualisation of complex 3D environments. Ph.D. thesis, National Centre for Software Technology, Juhu, Bombay, Indian, Feb. 1993.[5] P. Reilly and S. Shennan. Applying Solid Modelling and Animated Three-Dimensional Graphics to Archaeological Problems. Technical Report UKSC 209, IBM UK Scientific Centre, Winchester, Oct. 1989.