I know Cryengine 2 and 3 used to have a Voxel Editor feature where you could model caves in real time easily, but due to some bug problems it was patched out. The best possible way to create caves are through third party model programs like Blender or 3dsmax,maya, ZBrush etc. You will have to model lots of rocks or try make a shape of a tunnel and just place the meshes in the engine together so that the meshes form a tunnel. I hope this helps.
Furthermore landscapes support “hole” materials that allow you to essentially draw a hole in the landscape which you’d then replace with a static mwsh cave. You can’t directly carve caves into landscapes.
Another way is to use the “horizontal” hole by using the Landscape Visibility Mask node in your landscape material. Here is the documentation
When setting up the LandscapeVisibilityMask node make sure this is in your landscapes material and not a separate material. The images there do not indicate these are the same material. Once you have the material setup in the details panel for your landscape on the right hand side you’ll want to add the landscape material you made again in the “Landscape Hole Material” slot. This will allow you to use the Visibility sculpt tool to paint areas that are holes.
Ouch, 2014 sorry for spamming didn’t notice bc idea is so spot on! & Ya THIS, so old news to have to put a hole there, I get its been done apparently not easy, not on radar I suppose ,supply demand–but man SO need it right now,if my programming skills matchd artisti I’d BE there ;)) There is NO option that is desireable. I’ll make a new thread later.