Just put it wherever you want the terrain to stop rendering. Typically, it's done using a trigger zone when you enter a n indoor area. If you just want it done for the whole game then you can simply call it in a script that gets executed as soon as the player spawns. So, possibly put a trigger zone right where your player spawn point is and attach a script that calls this function.
System Specs: OS - Windows 7 Home Premium 64-bit SP1, CPU - AMD Phenom II X4 945, 3.0Ghz, RAM - 8Gb DDR3, GFX Card - 2048MB NVIDIA GeForce GT 640, FPSC-R Version - Beta 1.0085