each stroke can be undone when paiting terrain's height
each stroke can be undone when paiting terrain's height

JakubLukas/LumixEngine,gamedevforks/LumixEngine,gamedevforks/LumixEngine,JakubLukas/LumixEngine,dreamsxin/LuxEngine,galek/LumixEngine,zhouxh1023/LumixEngine,galek/LumixEngine,JakubLukas/LumixEngine,zhouxh1023/LumixEngine,dreamsxin/LuxEngine