Procedural Cave Tools
In Lays of Althas Sundered Order I made two tools for generating rocky terrain. The Tunnel Tool is a HDA that runs from within the engine to create Tunnel Sections in a procedural way. The Cavern Tool runs from within Houdini and turns any input geometry into an organic cave shape.
Overview of V1.0 of the tunnel tool.
Creates a natural cavern from any input geo.
Another example with additional merged in smaller cave.
In UE4 with some set dressing
Cavern in UE4
Cavern in UE4
Tunnel sections in Engine