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# Terrain

A terrain is available only at the scene level and represents the land relief (physical geography) on which rigid bodies can interact; only one terrain per scene is allowed.

A terrain consists of a set of tiles generated from a Graphics Gallery file, which you import in the Scene Editor.

The Editor uses a basic parametrization in order to subdivide the terrain's polygons into tiles. When you first import terrain file, and any time you need to edit the terrain object, you can change this default parametrization in these ways:

• By default the UV plane of the grid is mapped to the local XY plane of the terrain, which means that the local Z axis corresponds to the up axis in the simulation. You can change one or both of the UV axes to use any of the XYZ axes.
• You can change the default number of cells (which is 100) along the terrain's U and V coordinates.
• By default only one level of hierarchical subdivision is performed, but you can increase this by specifying a maximal number of subdivisions.
• If you enable hierarchical subdivision, you can also specify how many subcells to create, as well as a minimum number of triangles per cell to prevent further subdivision.

In addition, you can build a list of mapping rules that allow you to specify which materials are mapped to which textures, and you can also turn off shadow casting for the terrain to boost the resolution of your shadow maps.

Once set up, a terrain can be modified in terms of the parametrization, the material mapping, the shadow casting, and you can even specify an entirely new file to use.

## Sub-Topics

The following topics are covered in this section: