“perspective based level of detail management of topographic data”

““Perspective BasedPerspective BasedLevel of Detail ManagementLevel of Detail Management

of Topographic Data”of Topographic Data”

By: By: Morten GranlundMorten Granlund

Supervisor: Gunnar MisundSupervisor: Gunnar Misund

http://www.ia-stud.hiof.no/~mortengr

Level of DetailLevel of Detail

““Easing the burden of the 3D Easing the burden of the 3D renderer…”renderer…”

The basics of The basics of Level of DetailLevel of Detail

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

More on LoDMore on LoD

One square has a fixed data-sizeOne square has a fixed data-size A model is more accurate if:A model is more accurate if:

a)a) The model has more squares.The model has more squares.

b)b) Each square covers a smaller area.Each square covers a smaller area.

Tree StructureTree Structure

Level 0 Square covers >200 km

Level 1 Square covers 100-200 km

Level 2 Square covers 50-99 km

Rez…Rez… ……is an Open Source framework for is an Open Source framework for

translating terrain data.translating terrain data. ……creates Level of Detail hierarchies.creates Level of Detail hierarchies. ……creates two parallel hierarchies:creates two parallel hierarchies:

• TilesTiles• TreesTrees model

TilesTiles

Tree containing VRML Tree containing VRML datadata..• Each node is called a Each node is called a tile.tile.• Each tile contains a matrix with heights Each tile contains a matrix with heights

(elevation grid).(elevation grid).

World.wrl

World.wr

TreesTrees The Trees hierarchy contains the The Trees hierarchy contains the structurestructure.. The trees structure consists of a file hierarchy The trees structure consists of a file hierarchy

parallel to the tiles.parallel to the tiles. A trees node is a “wrapping” around each tile.A trees node is a “wrapping” around each tile.

0 1 2 3 4

World.wrl

World.wrlWorld.wrl

World.wrl

0 1 2 3 4

World.wrl

World.wrlWorld.wrl

World.wrl

A “Trees”-node has:A “Trees”-node has:

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

0 1 2 3 4

World.wrl

World.wrlWorld.wrl

World.wrl

0 1 2 3 4

World.wrl

World.wrlWorld.wrl

World.wrl

“perspective based level of detail management of topographic data”

square covers

trees node

terrain data tile node

lodone square

trees structure

vrml data

translating terrain

tilestreesthe trees

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