From the Project RDX:http://www.moddb.com/mods/project-rdx/downloads/blender-terrain-scripts
Blender scripts to turn an elevation grid into a terrain in .map format to be used in Radiant. hide detail -
To run the scripts, you should put them into the blender scripts folder.
The first script (split faces) is under "Mesh" category and, just like it says, splits the selected mesh in triangles (not advisable to use it with quads), creating a new mesh (named, indeed, "NewMesh").
The second ("Quake 3 (.map) - MODDED ") exports whatever you have selected into terrain.
Basically, each triangle is turned into a triangular prism, with the other face at a fixed height.
Now on the parameters:
-Scale: Self explanatory. How much to scale each blender unit compared to a Radiant unit.
For example with the default, 32, one units of blender becomes 32 units of Radiant (more or less the width of a player.)
-Base height: As said, each triangle of your grid is "extruded" into a prism. You already have one face, the other is a triangle with the same X,Y of each of the original face, and the Base Height as Z.
Long story short, how much far down to extrude your mesh. The value should be under the min height of the mesh (or over the max, if you are doing, for example. the top of a cave).
-Grid snap: rounds output values to integers.
-Null texture: base texture (or rather, shader) given by default. It is given to your mesh, for example
-Unseen texture: texture used, for example, in the other faces of the prism.