Level of Detail

As a Level of Detail (LOD; German: Level of detail ) refers to the different levels of detail in the representation of virtual worlds.

To increase the speed of applications of virtual reality, one usually starts on simultaneous use of fine detail at close range and low details at long range. This can reduce the complexity ( number of polygons ) of the 3-D objects which represent a number of draw calls as well as the resolution of the textures. The Mip mapping effect is not relevant for the optimization of the file, because the textures are loaded in full size in the memory of the graphics card.

Depending on the position and distance of objects to the observer the appropriate LOD is automatically selected. Standing only a few levels of detail available, the model change is possibly perceived by the sudden appearance and disappearance of details. To prevent the popping effect, continuous LOD be partly inserted into each other or transferred models by blending ( fading ) and morphing. For terrain models while Meshes come as Progressive used.

The example on the right, shows the sequence of several levels of detail of a building. The reduction is in all 3 areas:

  • Reducing the number of triangles
  • Minimizing the absolute size of each texture LOD level

In the field of virtual three-dimensional landscape and city models LOD techniques are used. Depending on the application, different levels of detail are needed here. The following levels of detail have been worked out for the CityGML specification and are currently many German city models are based:

  • LOD 0: regional model, 2,5 -D terrain models with aerial texture
  • LOD 1: Block model building block ( base pulled up )
  • LOD 2: 3D model of the outer shell and roof structures and simple textures
  • LOD 3: Architecture model, 3D model of the outer shell with texture
  • LOD 4: interior model, 3D model of the building with floors, interiors, etc. and textures
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