Starting version 5, WMSK allows you to use the Unity standard terrain itself into the Viewport slot:
When you assign your terrain to the “Render Viewport” slot, the WMSK gameobject will be moved away and controlled in a special way. Also your terrain will get a custom shader so it can blend the WMSK features along with the terrain splatmap textures.
The Resolution option allows you to adjust the resolution of the internal render texture used to capture WMSK’s features and imprint them onto the Unity terrain.
Filter Mode let’s you set the texture filtering option.
Alpha setting specifies the transparency of the WMSK’s features visible on the terrain map.
If you want to show the terrain splatmap textures instead of the Earth background texture, un-select “Show Earth” and increase the Alpha value. Once you do this, the country frontiers will be blended with the splatmap textures!
Check out the Terrain demos for examples (Demos/Terrain folder).