I'm asking this question because for my next project I need to implement a voxel terrain engine similar to that used in CryEngine 2. Because I need to make caves, no I have a mental system for how this could possibly work but if it does not could you suggest a work around?
My system is where the editor has an editing tool where I can instantiate low poly balls on top of each other without depleting to much memory. The way I found around that would be to use some sort of occlusion where it destroys certain balls on the inside
For example if I had three balls but you could not see the third then destroy the third ball since it is not needed.
If you want to do it yourself, look for Marching Cubes algorithm. It may take a day or two to wrap your head around, depending on your skill level. I managed to get this going the first day, and this going the second day. Third day I got bored and discontinued development of it.
Your idea of balls should be pretty simple to implement with marching cubes. Imagine each vertex has to sample a value (usually between 0 and 1) and that value is used to extend/retract the vertex for that point in space. Your balls would then interpolate from 1 to 0 where value 1 is in the center, and 0 is in the ball crust. Basically, you just have to check the magnitude.
I solved texturing by using a triplanar shader, requiring no UV coordinates. It just take the world position and project 3 textures on it, and interpolate between the textures depending on the normal.