Image Processing Reference
In-Depth Information
10.3.2.7 Procedures
The subjective experiments contained a training session and a test session. Five
pairs of stimuli were shown in the training session. The viewers were asked not to
stare at the moving object but to watch the whole stereoscopic sequence. Then, they
should select the one which is more uncomfortable, concerning e.g., mental uneas-
iness. The viewers used two distinct keys to select one of the two stimuli in a pair
for immediate visually check on the screen. There was a minimum duration for the
display of each stimulus before making a decision by pressing a specific third
button. The minimum duration is defined as either 5 s or the duration of a complete
cycle of movement (the moving object went back to its start point) whichever was
longer. During the training session, all questions of the viewers were answered. We
ensured that after the training session, all of the viewers were familiar with the
process and the task of this experiment.
In the main test session, 180 pairs were compared for Experiment 1, 210 pairs for
Experiment 2-a, and 105 pairs for Experiment 2-b. As the duration of each test was
different due to the number of pairs and individual differences of each viewer, and
to avoid visual fatigue caused by long time watching affecting the experimental
results, the Experiment 1 and Experiment 2-b were split into two sub-sessions. Each
session contained half of the total number of stimulus pairs. There was a 10-min
break between the two sub-sessions. For Experiment 2-a, the viewers were asked to
have a 15 min break after each 30 min of the test.
10.3.3 Results of Experiment 1: Influence of Motion
As in this experiment the paired comparison methodology was used, the obtained
results are paired comparison data for each pair. For better analysis, the Bradley-
Terry (BT) model [
43
,
44
] was used to convert the pair comparison data to
psychophysical scale values for all stimuli. The BT scores and confidence intervals
of all stimuli are shown in Table
10.3
. For easier comparison, the lowest BT score is
set to 0. The static condition can be considered as either a special case of the planar
motion or in-depth motion, both with the motion velocity of 0. Thus, in this section,
the static condition is analyzed in both conditions.
10.3.3.1 Planar motion and Static Conditions
The BT scores for the planar motion stimuli and static stimuli are shown in Fig.
10.6
where the static condition can be considered as a special case of the planar motion.
The experimental results on the planar motion stimuli showed that:
• Visual discomfort increases with the planar motion velocity;
