Pages in Rendering
Drawing voxels seems easy at a glance, they're just cubes after all!
However, there's actually an infinite amount of ways to render voxels, depending on the way they should look like, the underlying storage, performance and resource considerations, general method used, etc. etc. ...
It all depends on what you ultimately want to do.
Replacement of geometry that is too small with lower detail geometry.
Removal of geometry that is fully hidden behind other geometry.
Removal of geometry that is not in the same 'room'.
Similar to the problem of map projection, creating planets shows a fundamental problem with voxels: As they are regular grids, shaping the actual grid into a planet, without distortions or discontinuities, is mathematically impossible. As such, we need to employ different methods depending on what we ultimately want to achieve.
Back Face Culling
Removal of geometry not facing the camera.
Removal of geometry that is outside the cameras view region.
Removal of geometry that is too far away.
Modern hardware accelerated rendering API.
Classic hardware accelerated rendering API.
Removal of geometry hidden within geometry.
In general, (visibility-) culling is the process of limiting the amount of things rendered (both geometry and drawcalls) to manageable levels, so the GPU doesn't go up in flames.