The independent variables were the four travel techniques
described earlier and the dependent variables were the task
completion time, the total traveled distance and the number of collisions.
A collision is detected when a movement of the avatar towards
an obstacle causes a contact. Collisions are detected at each
frame, i.e. 60 times/s, thus implying a maximum of 60 collisions/s.
We used a within-subject design and trials were blocked by travel
technique. We counterbalanced the order in which participants
used each travel technique to minimize skill transfer effects. For
each travel technique (each block), the participants received brief
explanations by the experimenter, followed by two practices and
five trials.