public Terrain getTerrainAt(Vector3f worldLocation) {
        if (worldLocation == null)
            return null;
        Vector3f tileCell = getTileCell(worldLocation.setY(0));
        tileCell = new Vector3f(Math.round(tileCell.x), tileCell.y, Math.round(tileCell.z));
        return cache.get(tileCell);
    }
Get the terrain tile at the specified world location, in XZ coordinates.
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/TerrainGrid.java