run-time changeable landscape

Hello to all! I saw several video clips made on Unity in the style of the game "Minecraft", but it was clear that it was designed and configured in advance, not run-time generated. And how to implement on Unity "run-time" the generated and interactive (changeable by the player) landscape? I understand that for a beautiful picture you need to “lick” every corner, bake shadows, adjust textures, etc., but if you focus not on the photo-realistic picture, but on the “indie” world? If there are examples or a description of the technology, please share the links.