The Visual Computer

, Volume 31, Issue 4, pp 407–421 | Cite as

Optimizing line-of-sight using simplified regular terrains

  • Troy AldersonEmail author
  • Faramarz Samavati
Original Article


In this work, we explore a set of techniques for speeding up line-of-sight queries whilst attempting to maintain accuracy. Line-of-sight queries, which test if two entities can see each other over a 3D terrain model, are an important operation in several applications. Given enough entities and a large enough terrain, computing these queries can be expensive. We apply reverse subdivision methods to simplify the terrain model and speed up the queries, including a novel feature-aware reverse subdivision scheme. To counteract the loss of accuracy due to simplification, we also examine the problem of where entities should be placed after terrain simplification to increase accuracy. Using iterative methods that attempt to maximize accuracy, we show that room for improvement exists over the standard projection method. Then, using residual multiresolution vectors, we develop a relocation method designed to maximize accuracy over simplified terrain models. Finally, we present a fast line-of-sight algorithm that combines these techniques with pre-existing algorithms.


Line-of-sight Terrain simplification Multiresolution Subdivision Reverse subdivision 



Our thanks go out to C4i Consultants, Inc. for motivating the problem, assisting in research, and providing SRTM terrain data. Our thanks go also to the Mitacs Accelerate program for sponsoring the collaboration. Terrain map images were generated with Global Mapper software. Conceptual figures were created using Inkscape.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.University of CalgaryCalgaryCanada

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