code: function(x,z,h){
  				var index = this._getIndex(x,z);
  				this.elevation[index] = h;
  				this.vertices[index].y = h;
  				return this;
  			}
docs: Sets the elevation for a single given grid cell.
  @param {Number} x
  @param {Number} z
  @param {Number} h new elevation value
  @return itself