Multi-resolution Triangular Mesh (MTM) models are widely used to improve the performance of large terrain visualization by replacing the original model with simplified one. MTM models, which consist of both original and simplified data, are commonly stored in spatial database systems due to their size. The relatively slow access speed of disk makes data retrieval the bottle-neck of such terrain visualization systems. Existing spatial access methods proposed to address this problem rely on

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... emory MTM models, which leads to significant overhead during query processing. In this paper, we approach the problem from a new perspective and propose a novel MTM called Direct Meshes that is designed specifically for secondary storage. It supports available indexing methods natively and requires no modification to MTM structure. Experiment results, which are based on two real-world datasets, show an average of 5-10 times performance improvement over the existing methods. Index Terms Multi-resolution visualization, spatial database systems