We postponed the creation of wheels in the game for as long as possible, since we wanted to keep to our guideline of having as few custom shapes as possible to make building very flexible. Custom shapes can lock the player into having to plan the structure more. Eventually we had to insert them because, well, it would be really FUN to make monster-trucks that can climb the hills or put wheels on a rocket-powered airplane 🙂
The current solution is not optimal and is kind of a hack but actually works fine for now, and that is to render the wheels as pure voxel shapes like all other blocks (as seen in the image above) but the physics simulation believes they are somewhat oversized cylinders. So they roll just like they should even though they seem square. The oversize also provides some amount of ground clearance. We have some other ideas that we might include further on to improve on the ground clearance without increasing the mismatch between the visible shape and the simulated shape.
You can attach the wheels to motors that are either powered or un-powered (in which case they will just roll like attached to a low-friction bearing and mount). Also, the player, other characters and objects are of course affected by the wheels so it’s possible to make other creative things except for vehicles that roll on the ground..