AStudy On The ErrorMetric Of Generating LOD Of Terrain

Efficient interactive visualization of very large digital elevation models (DEMs) isimportant in a number of application domains, such as virtual reality, GIS, and militarysimulation. Presently, due to limited hardware capacity for the large-scale terrain, thereal-time modeling and visualization still can not meet the needs of real-timeinteraction.Multi-resolution terrain representation is a good way to simplify terrain to realizereal-time rendering. To minimize the complexity of terrain model and the number of renderedtriangles, there are two problems lie in real-time terrain rendering:one is which effiective datastructure to be chosen for constructing the terrain surface, so as to generate and render terrainmodel easily, the other is which more effective error metric to be chosen, for reasonablecompromise between high fidelity and quick generation of LOD model. Aim at this twoproblems, this dissertation was based on the analysis and researchment of terrain renderingtechnologies and error metric for extraction of LOD model. Taking the characteristics ofdynamic terrain application into account, this paper carried out analysis and researchmentcentering on the multi-resolution, region preservation and so on.1. Methods for modle simplification, multi-resolution representation and rendering ofterrain are investigated, take triangular bintree structure to construct terrain model by theDEM sampling height, generate static entire static full-resolution terrain mesh, renderthree-dimensional terrain in the field of view according to the position of viewpoint and theerror metric.2. On the basis of analyzing various methods of calculating error metric, present animproved calculation of error metric based on the roughness. Take roughness which expressthe fluctuation of terrain to be an factor, calculate error metric, form the sphere of error metricaccording to the position of viewpoint, choose appropriate LOD model on every frame. Theexperiment results show that our algorithm reduces the rendering triangles required, and fits the uneven terrain better.3. To prevent the distortion of details of outline when overlooking terrain in a longdistance, take a strategy that reducing the error in low-lying region. In order to eliminate asmall amount of cracks in the triangular grid model, change the states of some vertexes, thealgrithm ensured rendering correctly of the entire outline of terrain when overlooking. Fordynamic terrain, the expansion of accuracy of changed cell achieves rendering deformedterrain real-timely, and the error of some vertexes including introduced vertexes are modifiedaccordingly.Finally, this method was verified through some experiments, comparing with the formermethods for number of triangulations required and fidelity of terrain rendering. Theexperimental results indicated that this method could reduce the rendering triangles required,maintain integrity of terrain and higher effect of rendering.