Development and evaluation of a test setup to investigate distance differences in immersive virtual environments

Nowadays, with recent advances in virtual reality technology, it is easily possible to integrate real objects into
virtual environments by creating an exact virtual replication and enabling interaction with them by mapping the obtained tracking
data of the real to the virtual objects. The primary goal of our study is to develop a system to investigate distance differences for
near-field interaction in immersive virtual environments. In this context, the term distance difference refers to the shift between
a real object and the respective replication of the real object in the virtual environment of the same size. This could occur
for a number of reasons e.g. due to errors in motion tracking or mistakes in designing the virtual environment. Our virtual
environment is developed using the Unity3D game engine, while the immersive contents were displayed on an HTC Vive Pro headmounted display. The virtual room shown to the user includes a replication of the real testing lab environment, while one of
the two real objects is tracked and mirrored to the virtual world using an HTC Vive Tracker. Both objects are present
in the real as well as in the virtual world. To find perceivable distance differences in the near-field, the actual task in the
subjective test was to pick up one object and place it into another object. The position of the static object in the virtual
world is shifted by values between 0 and 4 cm, while the position of the real object is kept constant. The system is evaluated by
conducting a subjective proof-of-concept test with 18 test subjects. The distance difference is evaluated by the subjects through
estimating perceived confusion on a modified 5-point absolute category rating scale. The study provides quantitative insights
into allowable real-world vs. virtual-world mismatch boundaries for near-field interactions, with a threshold value of around 1 cm.