In Godot V2 there were Rooms & Portals to segment your maps/levels and reduce overdraw using an automatic "skipping-scheme" for the parts of the level that are occluded by parts that are closer to the viewer. It seems these nodes doesn't exist anymore in Godot V3. What is the recommended way of doing something like that in Godot V3? If have a big map with hundreds of interconnected rooms I absolutely don't want to always render all 100 rooms but only the rooms that are visible from the current rooms the player resides in. How can I accomplish that in Godot V3?