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Distributed Handling of large Level of Detail Surfaces

Distributed Handling of large Level of Detail Surfaces. Using binary triangle trees and progressive streaming. Rune Aasgaard Thomas Sevaldrud SINTEF Applied Mathematics. Several ways to the goal. Centralized rendering, image distribution Client-server terrain database. Which data where?.

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Distributed Handling of large Level of Detail Surfaces

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  1. Distributed Handling of large Level of Detail Surfaces Using binary triangle trees and progressive streaming. Rune Aasgaard Thomas Sevaldrud SINTEF Applied Mathematics

  2. Several ways to the goal • Centralized rendering, image distribution • Client-server terrain database

  3. Which data where? • Client terrain database • Near graphics system • Some simple analysis functionality • Fast updates • Server terrain database • Huge! • Fast access • Updateable / re-generateable?

  4. Level of Detail • A coarse model retained for the whole domain • Use already transferred data • Refinement until required quality obtained • Coarsen when possible • Keep recently coarsened data in cache

  5. RequirementsClient terrain model • Closeness to graphics system • Triangle sets • 3D coordinates • Texture coordinates • Normal vectors

  6. RequirementsClient terrain model • Simple analysis functionality • Connectivity • Single elevations • Profiles • Gradients

  7. RequirementsClient terrain model • Updates from server when: • Data becomes visible • More detail is required • Reduce to coarse level when: • Data becomes invisible • Less detail is required

  8. RequirementsServer terrain model • Huge! • Whole earth, 30” grid (DTED Level 0): 933.120.000 points! • Whole earth, 3” grid (DTED Level 1): 93.312.000.000 points! • Luckily, 2/3 of the earth is ocean • Major parts of the land is relatively flat

  9. RequirementsServer terrain model • Fast access, query expectations: • Grouped • Localized in area • Similar resolution level

  10. RequirementsServer terrain model • Model creation and editing, data sources • Variable quality • Variable density • Variable complexity • … integration…?

  11. Selected solution- client • Binary triangle trees • Related to Lindström triangulations and ROAM algorithm • Simple algorithm for triangle fan creation • Simple relation between triangles and texture quads • Error sphere tree instead of priority queues

  12. Binary Triangle Trees- refinement split

  13. Binary Triangle Trees- forced neighbor split

  14. Error sphere tree • Acceptance radius based on • Angular resolution • Triangle approximation error • Centered at triangle split point • May be common for triangle pair • Uses maximum radius • May contain child spheres • Also contains object radius

  15. Error sphere tree

  16. Selected solution- server • Quad trees • Easily transformable to BTT • Fast access system for disk based data • Simple algorithm for creation and updating with more detailed data

  17. Server Quad tree

  18. Selected solution- communication • Query • indexed on coordinates • collected as a query set • Reply • Elevations • Approximation errors

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