参考：https://forums.unrealengine.com/community/community-content-tools-and-tutorials/26436-tutorial-fog-of-war?55650-TUTORIAL-Fog-Of-War=
参考：https://forums.unrealengine.com/community/community-content-tools-and-tutorials/26436-tutorial-fog-of-war?55650-TUTORIAL-Fog-Of-War=