Automatic reconstruction and visualization of a complex Buddha tower of Bayon, Angkor, Cambodia

Abstract

The Hindu and Buddhist monuments of Angkor in Cambodia are the legacy of highly developed Khmer empires. Well-known for their structural and surface complexity they constitute a great challenge to any attempt towards precise and detailed 3D measurements and modeling. This paper reports about a pilot project using modern techniques of analytical and digital photogrammetry to derive a photorealistic 3D model of one of the very complex towers of the famous Bayon temple of the ancient city of Angkor Thom. This high quality model will then be subject to visualization and animation. On occasion of a balloon photogrammetry mission over the Bayon temple of Angkor , the first author took a number of tourist-type terrestrial images with a Minolta Dynax 500si analogue SRL camera of one of the many Buddha-faced towers of Bayon . We aim at deriving automatically, after scanning of the images, a texture mapped 3D model of the very complex object. In a first step we have generated already such a model with a mixture of manual (phototriangulation) and automated procedures (image matching for surface reconstruction, editing for blunder removal, texture mapping, visualization and animation). This result has been presented in Visnovcova et al., 2001 and includes already some novel methods for point cloud blunder editing and view-dependent texture mapping. Now we will include more images than before, intend to automate the phototriangulation procedure, develop a matching approach based on MPGC (Multiphoto Geometrically Constrained) Matching and also improve the procedure of color texture mapping. With these combined new approaches we expect a higher level of completion of the object, an improvement of the modeling quality and a shortening of the processing time to generate the 3D model. We streamline our new method of point cloud editing and improve our new technique of view-dependent texture mapping. Finally we show how different forms of high quality visualization techniques can be used on low-cost platforms. The ultimate goal of this activity and investigation is to develop a system that is capable of producing high quality photorealistic 3D models in fully automated mode. 1 Introductionthe 9 th and 15 th centuries A.D. a succession of 42 kings ruled over one of the most remarkable empires in human history: The Khmer empire of Angkor in Cambodia.What used to be before and after an endless stretch of tropical jungle was turned into 75 square miles of fertile plains, with 72 major monuments, temples, palaces, canals with dikes, moats, and reservoirs. A sophisticated irrigation system, controlling equally abundant waters from monsoon rains and yearly droughts, provided for two to three rice harvests per year, feeding at times up to one million inhabitants. Today it is one of the most spectacular sites listed in the UNESCO World Heritage List (DAGENS, 1995, MALRAUX, 1930, MOUHOT, 1864, MOORE, 1960, PRESTON, MCCURRY, 2000). While statutes and other treasures were shipped off from the site from the very beginning of European interference, extensive excavations and renovation works have been under way 1 Institute of Geodesy & Photogrammetry, ETH-Hoenggerberg, CH-8093 Zurich, Switzerland,