rectangular gain for HTC vive

hi i'm a student in game design and i'm doing a project in VR with the HTC vive, and we got a issue, the room scale is to small for the the type of game we want to do. We got the biggest room scale setup possible but its still too small. I've done some research, and a way to make it bigger is with a rectangular gain :

the question is how to do this? i'm a code beginner and i'm kinda lost so if you help me out i'll be so gratefull