MoleEngine features smooth and fully destructible voxel-based terrain. The package provides two algorithms, Dual Contouring and Marching Cubes, this way the it can be used for highly detailed voxel terrains as well as low-poly terrains for mobile applications.
Automatic paging (loading and saving on the fly) is available as well as procedural terrain generation. Unlike other smooth voxel terrain packages MoleEngine features multiple materials ( a sample shader for up to 16 textures is included ).
For an in-detail description visit our thread in the Unity Forums.

Demos
Flat Terrain
Procedural Terrain
Floating Rock
Cubical World
Normal Mapped Shader