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Perspective BasedLevel of Detail Managementof
Topographic Data

• By Morten Granlund
• Supervisor Gunnar Misund

http//www.ia-stud.hiof.no/mortengr
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Level of Detail

• Easing the burden of the 3D renderer

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The basics of Level of Detail

• GOAL Render 3D graphics fast!
• SOLUTION Several levels of detail.

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More on LoD

• One square has a fixed data-size
• A model is more accurate if
• The model has more squares.
• Each square covers a smaller area.

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Tree Structure
Level 0 Square covers gt200 km
zoom
Level 1 Square covers 100-200 km
?
zoom
Level 2 Square covers 50-99 km
?
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Rez

• is an Open Source framework for translating
  terrain data.
• creates Level of Detail hierarchies.
• creates two parallel hierarchies
• Tiles
• Trees

model
tiles
trees
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Tiles

• Tree containing VRML data.
• Each node is called a tile.
• Each tile contains a matrix with heights
  (elevation grid).

tiles
0
1
2
3
4
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Trees

• The Trees hierarchy contains the structure.
• The trees structure consists of a file hierarchy
  parallel to the tiles.
• A trees node is a wrapping around each tile.

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A Trees-node has

• Reference to Parent node
• Reference to Children nodes (x4)
• Reference to the terrain data (tile node)