Current Virtual Reality systems only allow users to draw a rectangular perimeter to mark the room-scale area they intend to use. Domestic environments can include furniture and other obstacles that hinder the ease with which users can naturally walk. By leveraging the benefits of passive haptics, users can match physical objects with virtual counterparts, to create substitutional environments. In this paper we explore two visualisation modalities to aid in the creation of a coarse virtual representation of the physical environment, by marking out the volumes of space where physical obstacles are located, to support the substitution process. Our study investigates whether this process is better supported by an inside-looking-out 3D User Interface (that is, viewing the outside world while immersed in Virtual Reality) or from an outside-looking-in one (while viewing the Virtual Environment through an external device, such as a tablet). Results show that the immersive option resulted in better accuracy and was the one with the highest overall preference ratings.