TerrainData.GetSupportedLayers  

function GetSupportedLayers (xBase : int, yBase : int, totalWidth : int, totalHeight : int) : int[]

Description

Returns an array of all supported detail layer indices in the area.

The Terrain uses a detail layer density map. Each pixel in the map the amount of details objects that will be procedurally placed in the pixel area. The layer determines the detail prototype that will be instantiated at the location.