Via: https://steamcommunity.com/games/250820/announcements/detail/2471861771402099478
SteamVR 1.13 introduces a new experimental feature for Valve Index users, "Room View 3D".
Room View 3D uses computer vision techniques developed by Valve, Arcturus Industries, and Occipital to present a more accurate representation of your environment.
To enable this functionality, select Room View: "3D" from Settings -> Camera.