How did Zero Horizon render only what was in the camera's view?

Hi guys! Recently I was watching a gaming video and it mentioned that in the PS4 game Zero Horizon, it only renders whatever is in view of the camera while everything else is unrendered. I tried to find the video of this(which I swear I saw on YouTube a short while back but I can't find it now)

My question is, how do they do this? Is there a script attached to the camera, is it on another layer? I'm certainly not new but I'm not a pro(working on my first indie game) and my world is open very much like skyrim but with lots of large trees and I think this would help the game run smoothly without losing that quality.

Also if this is tagged incorrectly or in the wrong spot, please let me know. I very rarely post on here and I do my best to mark everything properly but if there's any issues I will fix them

 

Things not in the camera's view frustum are culled automatically. What I think you're referring to is occlusion culling, where things that are within the camera's view frustum but obscured by other geometry (like a wall) are culled. The linked article will discuss how to set it up.

 

Awesome thank you so much I'll be sure to check it out!