| || Real-time Photorealistic Visualisation of Large-scale Multiresolution Terrain Models
Author : Agrawal, Anupam ;Joshi, R. C. ;Radhakrishna, M.
Source : Defence Science Journal ; Vol:57(1) ; 2007 ; pp 149-162
Subject : 550.3 Geophysics
Keywords : Level-of-detail management;Multiresolution modelling;Real-time rendering;Photorealistic visualisation;Terrain-rendering algorithm;Digital terrain models
Abstract : Height field terrain rendering is an important aspect of GIS, outdoor virtual reality applications such as flight simulation, 3-D games, etc. A polygonal model of very large terrain data requires a large number of triangles. So, even most high-performance graphics workstations have great difficulty to display even moderately sized height fields at interactive frame rates. To bring photorealism in visualisation, it is required to drape corresponding high-resolution satellite or aerial phototexture over 3-D digital terrain and also to place multiple collections of point-location- based static objects such as buildings, trees, etc and to overlay polyline vector objects such as roads on top of the terrain surface. It further complicates the requirement of interactive frame rates while navigation over the terrain. This paper describes a novel approach for objects and terrain visualisation by combination of two algorithms, one for terrain data and the other for objects. The terrain rendering is accomplished by an efficient dynamic multiresolution view-dependent level-of-detail mesh simplification algorithm. It is augmented with out-of-core visualisation of large-height geometry and phototexture terrain data populated with 3-D/2-D static objects as well as vector overlays without extensive memory load. The proposed methodology provides interactive frame rates on a general-purpose desktop PC with OpenGL- enabled graphics hardware. The software TREND has been successfully tested on different real-world height maps and satellite phototextures of sizes up to 16K*16K coupled with thousands of static objects and polyline vector overlays.