Unity spherical flat voxel terrain

Hello, we need a voxel terrain, but it needs to be a self-loop. When the player moves straight ahead, he must return to the point where he started. Optimization is important to us, so as the player progresses, the map in front of him must be loaded.

Example: Eco Global Survive Game. https://play.eco

Important Note: The game will be online. Cloned terrain is not prefer.