Not sure what the cause is but when using the API's for terrain, I get either black billboard grass or no grass being rendered.
If I call ccbUpdateTerrain(terrainnode) then I get black grass billboard textures.
If I follow this call with ccbSetTerrainTexHeight(terrainnode, 0.15, 0.60);
then all the grass is missing from the rendered terrain.
Also, I'm not quite sure what ccbSetTerrainSmoothing(terrainnode,40); does as there is not any documentation for it and I cannot see any changes in terrain with it set.