(script) how to get terrain to turn into blocks

I need a script to make the terrain to turn into blocks but keep the terrain. and make it so it removes the renderer of the cubes so that it increases performance. i need t$$anonymous$$s so that i can place blocks on the terrain like a minecraft style game. i need the cubes to instantiate automattically when game starts. I am okay at programming but i aint good enough to do t$$anonymous$$s.