As we have seen, holes can be painted in Terrain meshes, as simply as we can height- and texture-paint terrains. Adding holes opens up a wide range of features we can add to scenes, allowing us to make complex combinations of one or more terrains with other scene objects and geometry.
When created, the edges of holes in terrains are unsightly, and in most games, they will need tidying up. In this recipe, we used four cubes positioned and scaled to form a neat entrance and channel from the surface of the terrain, down to the bonus Cube level. For a more natural entrance to a Terrain hole, you could use a pre-existing 3D model or a custom mesh that's been textured using the ProBuilder Unity tools.