-- 保存到文件
function cc.HeightFieldComponent:save(fileName)
	local xml = {};

	xml.HeightMin = self:getHeightMin();
	xml.HeightMax = self:getHeightMax();
	xml.GridSize = self:getGridSize();

	local box = self:getBoundingBox();
	xml.BoundingBox = {min = box:getMin() ; max = box:getMax()};

	xml.HeightFieldFile = fileName .. ".png";

	local heightField = self:getHeightField();
	heightField:saveToPNG(xml.HeightFieldFile);

	table.saveFile(xml , fileName);
end

-- 从文件载入，并创建HeightFieldComponent实例
function cc.HeightFieldComponent:load(fileName)
	local xml = table.loadFile(fileName);
	local heightField = cc.HeightField:createFromImage(xml.HeightFieldFile
														, xml.HeightMin
														, xml.HeightMax
														);
	local component = cc.HeightFieldComponent:create(heightField 
											, cc.BoundingBox:new(xml.BoundingBox.min , xml.BoundingBox.max)
											, xml.HeightMin
											, xml.HeightMax
											, xml.GridSize
											);
	component:_notifyFileName(fileName);
	component:_notifyHeightMapPath(xml.HeightFieldFile);
	return component;
end