Caves add a lot to the map without directly increasing the size of the map, they could be a tiny hole in the mountain to a long cave with many dangerous creatures to giant holes filled with wonder
To make a cave inside the landscape go to the landscape tool, and change the tool to invisible then make a hole in the landscape, it will take abit to render (if no hole is shown and it becomes a grey tile instead then you are missing the “Hole” material on your landscape, see the basic are above on how to add this)
With your hole made you shape the entrance using rock meshes to make it blend properly with the landscape, the entire cave is also built using rock meshes, If you are making a rather large cave then you could also make another landscape and place it inside and shape as well as possible.
Do note for larger caves it is advised that you create a new umap such as A1_Cave
There are 2 volumes you must have in your caves for it work properly, for smaller caves you only need 1
You need a “structure prevention zone volume” this volume should encase your entire cave and a little bit outside the entrance, This volume does 2 important things, It prevents the player and dino’s from being teleported out due to being under the landscape and it prevents building if the server has “prevent building in caves” enabled
The second volume you need a postprocessvolume this volume needs a bit more planning to get right as you need to place it in such a way that it covers the entire cave but not the entire entrance, it should be placed in such a way that when you enter it you can no longer look out as we will be disabling the sky and similar.
This volume will set the player state as “in cave”, turn the sun off, turn the truesky off, turn the fog off and disable the rain sound while inside the cave, this is done for realism as the sun should not cast shadows inside the cave. This is achieved through the level blueprint.
Make sure the 2 volumes are on the persistent level so they can be referenced inside the level blueprint then re create the following inside your blueprint
For the second image you need to have the postprocessvolume selected then right click and create a OnPostProcessVolumeEntered and OnPostProcessVolumeLeft and link them to the sequencer as shown in the images above
You can use the same method to add caves under water, if you want there to be water then you wont need the postprocessvolume if you want there to be a airlock and no water you will need the postprocessvolume and a physical volume to disable swimming once you enter it.
You can also make dry caves from land going far beneath the ocean level, to achieve this you need to cut a hole in the mesh that is your ocean, to do this you need a program such as Modo or blender or any 3d editing program of your choice.