The virtual reality task was programmed using UnrealEngine2 Runtime software (Epic Games; http://udn.epicgames.com/). The unit for all coordinates is the virtual meter (1 vm = 62.5 Unreal Units). Participants navigated in a first person view within a 3-dimensional virtual environment (VE) as shown in Fig. 1A. While participants were lying in the MRI scanner, the VE was projected using a back projection
system with a set of mirrors. Navigation was controlled using a MR-compatible joystick (NAtA Technology, Coquitlam, Canada). The environment consisted of a grass plane surrounded by a circular stonewall (i.e., the boundary; diameter: 180 vm), a traffic cone (a landmark) and distal orientation cues (landscape of mountains, clouds, and the sun; projected at infinity, see Schuck et al. (2013a)). Walking speed was constant and allowed the participant to cross the entire arena in about 15 s. Coordinates of the present location within the VE were recorded every 100 ms.
https://schucklab.gitlab.io/docs/papers/Schuck_etal_2015_NeuroImage.pdf