LODTreeExport format specifications
version 1.1
About this document
This document describes the specifications of the LODTreeExport format.
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The LODTreeExport format describes an exported LOD bad textured mesh.
A LOD bad textured mesh is a single 3D model made of independent tiles of data; each tile itlf is made of a tree of levels of detail (LOD).
The LODTreeExport format is made of a root directory containing XML documents, subdirectories, and model files.
The root XML document “LOD l” describes the whole datat including the coordinate system and the list of tiles. Each tile is stored in a distinct sub-directory: an XML document describes the LOD tree structure of the tile, and standard 3D model files (DAE, 3DS, OBJ…) store 3D models corresponding to levels of details.
Example of LODTreeExport folder:
Example of tile sub-directory “Tile_+002_+003”:
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LODTreeExport root (XML document)
英杰风景区This XML document is the datat header including coordinate system and tile list.
Tiles and corresponding model files are stored in specific sub-directories containing for each tile, the tile XML description and the corresponding standard 3D files (may change according to export options).
<SRS>
Spatial Reference System: defines the EPSG code or the WKT definition of the cartographic projection system ud for the coordinate system.
The SRS tag may be empty is the model is not geroeferenced.
<Local>
Defines coordinates of the origin in the given SRS.
All coordinates further in the export are metric and relative to this origin.
If the SRS is not metric, a local –cartesian- ENU (East-North-Up) system centered on the LODTreeExport local origin is ud instead. See also Coordinates.
<ModelOriginMode>
Obsolete
Always t to NodeCenter.
List of <Tile>
Describe the list of tiles of the LOD tree datat. Tile contents are described in independent XML files.
The LODTreeExport may contain one or veral tiles
Attribute ‘name’
Name of the tile.
Attribute ‘p ath’黑龙江高考时间>怎么办歌词
Relative path of the external XML file describing the tile (Tile content).
Tile content (XML document)
This XML document describes the tile content. It referenced external 3D model files stored in the same directory.
<Tile>
Describe the tile content. Inherits from Node.
Only one tile is described in tile XML document.京剧男旦
Attribute ‘name’
Name of the tile.
Inherited properties
The Tile object inherits from all Node properties: MinRange, Radius, Center, ModelPath, and list of Node. See below.
<Node>
<MinRange>
Provides the validity range of the node in pixels (pixel distance on screen).
The validity depends on the on the node size on the screen.
<Radius>
Radius of the node bounding sphere in meters.
<Center>
Coordinates of the center of the node bounding sphere relative to LODTreeExport <local>, in meters.
See also Coordinates.
<ModelPath>
暴珍天物Relative path of the model file corresponding to the node.
The model file is a standard 3D file (DAE, OBJ, etc.).
Vertices in the model file are given in meters relatively to the he node <Center>. See also Coordinates.
Note: the tag <ModelPath> may remain unspecified if the node has no attached model. Empty nodes
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may appear in the tree becau of geometry simplification (a node can be empty in one level and not empty in the following level).
List of <Node>
Define the direct children of this node, the list may be empty.
Model files
Model files are standard 3D files (DAE, OBJ, etc.), directly saved in the tile directory.
Each model file is attached to one node in the tile tree.
Format
The file format may change according to export option: DAE, OBJ, etc.
Coordinates
All coordinates in the export are metric and are bad on the LODTreeExport local origin and LODTreeExport SRS.
If the LODTreeExport SRS is metric: coordinates in the model file are given in meters relatively to the node <Center>, which is itlf relative to the export local origin.
For a given position p_model(x,yz) in the model file, the absolute coordinates p_abs in the LODTreeExport SRS will be:
p_abs = exportLocal + nodeCenter + p_model
If the LODTreeExport SRS is not metric (eg. WGS84), a local –cartesian- ENU (East-North-Up) system centered on the LODTreeExport local origin is ud instead.
For a given position p_model(x,yz) in the model file, the local coordinates p_local in the LODTreeExport local ENU system will be:
p_local = nodeCenter + p_model
File name
The files needed to save one model can change according to the 3D format and saving options; texture files may appear as extern files (jpg files…).
