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LOD files are 3D shapes that get progressively simpler and are tied together by a common name:

file.3ds / fileLOD1.3ds

If an object uses a 3D shape that has LOD then the 3D shape that the object displays is dependent on how far that object is from the view's camera position.

  • 0 is the base LOD “file.3ds”
  • 1 is the 2nd LOD “fileLOD1.3ds”
  • 2 is the 3rd LOD “fileLOD2.3ds”
  • N is the nth LOD “fileLODn.3ds”

LOD Files are used to show higher level objects when the viewer is close up and lower level objects when the viewer is farther away. LOD improves the speed at which a model will display in the view window. LOD allows for the use of more polygon intensive 3D shapes by displaying only a few high polygon count shapes at any given time.

Preparing LOD Files

To prepare a group of 3D Shapes for use as an LOD file do the following:

  1. Gather together two or more shapes that you want to use as LODs of the same object.
  2. Get the LOD files saved as the same file type (3ds, wrl).
  3. Make sure that each LOD uses or at least isn't disfigured by the base file's .xds file (each frame can have it's own .yds file).
  4. Name the LOD files appropriately. The first file is the “name.3ds” or “name.wrl”. Each successive file is “nameLOD#.3ds” or “nameLOD#.wrl”. For example, Queue.3ds, QueueLOD1.3ds, QueueLOD2.3ds, etc.

To import an LOD shape just follow the steps used in the section on Importing 3D Media. Use the base object for the name of the file that you select.


lds / lrl files are used to determine the distances at which the different LOD's will be shown. lds / lrl files must have the same names as the objects they modify:

  • crane.3ds –
  • crane.wrl – crane.lrl

lds / lrl file info

The lrl/lds file is a text file made up of three numbers separated by new lines: The range perspective value, the range perspective mode, and the range ortho value.

  • The range perspective value is the distance value at which the LOD files will change in the perspective window.
  • The range perspective mode value is either 1 or 0. 0 means linear (slightly faster). 1 means inverse distance (more coverage at farther distances).
  • The range ortho value is the distance value at which the LOD files will change in the ortho window.

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paul.t contributed to this article


FlexSim 2016.1