public TerrainLayerSmoothnessSource smoothnessSource { get; set; }

Used for choosing where smoothness value comes from when TerrainLayer.diffuseTexture has an alpha channel. Setting to TerrainLayerSmoothnessSource.ConstantMultipliedByDiffuseAlpha results in using a mix of the smoothness value set in TerrainLayer.smoothness and of the TerrainLayer.diffuseTexture alpha channel. Setting to TerrainLayerSmoothnessSource.DiffuseAlphaChannel results in using the smoothness value set from the alpha channel of TerrainLayer.diffuseTexture. Setting to TerrainLayerSmoothnessSource.ConstantOnly results in using the smoothness value set in TerrainLayer.smoothness.