The experiment took place using the same setup as the analyses of HMD oscillations described earlier. As illustrated in Figure 4, the VE was rendered using the Unity3D engine and showed a simpli ed outdoor scene with two di erent targets subsequently displayed on the ground. Depending on the condition, after reaching the rst target, the second target was displayed 90◦ to the right or left. We speci cally chose a simple scene that did not provide any signi cant landmarks that might either distract the participants or give them additional cues about their location and travelled distances, other than the targets. However, the ground texture provided e ectual optic ow information for participants to estimate their motions when moving through the VE. Similar VEs have been used for several distance and motion perception experiments [13, 26].