One of the major features of the game is the ability for players to manipulate the world around them. Minecraft achieves this by using large voxels (aka volume pixels) to construct the world. This allows players to dig tunnels and caves and generally works pretty well for providing a world that players can manipulate.

The problem with this approach however is that voxels will take up quite a bit of memory and will also take up a lot of polygons on the screen, even after expensive greedy meshing algorithms that attempt to reduce it. This means that the view distance and performance suffers. In Minecraft, Voxel based terrain is well worth the cost because a key component to its gameplay is digging caves and mining. View distance is less of an issue since the majority of a players time will be spent underground. However this is not the case for Once we Were Nomands.

In OWWN, view distance is front and center for creating an engaging world. Being able to see distant terrain features and structures is key to the exploration of the world. While Minecraft's view distance wasn't bad, OWWN, will blow Minecraft's view distance out of the water by being able to see distant mountains on the horizon. Additionally, digging and mining is not a core gameplay mechanic in OWWN. So all of the effort expended on a voxel based terrain system would be wasted. Even if we allowed for unlimited digging like in Minecraft, we would want to encourage players to build on the surface anyway so we would not have to deal with many of the war-time tunneling issues that had to be dealt with in CivilizationCraft.

A compromise to this is to simple use a heightmap for the terrain, but allow voxels to be placed in a grid on top of it. You can see a demonstration of that in a very early alpha video I've made here: http://www.twitch.tv/avr_gaming/b/538867682

Unlike other heightmap engines though, we're intentionally keeping the amount you can lower and raise individual points discrete. This allows players to more easily design their environment(as opposed to sculpting it) and gives that satisfying "snap" that Minecraft has when manipulating terrain features. It also contributes to our desired look and feel for the game, which will remain fairly light hearted and cartoon-like.

Heightmaps are also well established in the industry and many techniques exist for implementing improvements like Level Of Detail optimizations which are critical for creating large view distances while maintaining performance.

Feel free to leave any questions or comments you have about the grid terrain system.