The Importance of Visual Attention in Improving the 3D-TV Viewing Experience: Overview and New Perspectives <s> B. Studies of Visual Attention in Stereoscopic Content <s> Humans select relevant locations in a scene by means of stimulus-driven bottom-up and context-dependent top-down mechanisms. These have mainly been investigated by recording eye movements under 2D natural or 3D artificial stimulation conditions. Here we try to close that obvious gap and presented 2D and 3D versions of natural, pink, and white noise images to human subjects. Importantly, ground truth distance was obtained for all image pairs by laser scanning. Recording eye movements, we investigated the influence of disparity information and of higher order scene correlations on basic saccade properties and on saliency of bottom-up information. Our results show that the removal of higher order correlations changed saccadic rate, length and main sequence, and the subjects’ explorative behavior. Introduction of disparity information countered these effects and alleviated differences between image categories. Disparity information had no effect on the saliency of monocular image features like luminance and texture contrast; however, without higher order correlations these features were uncorrelated to fixation locations. An analysis of binocular image features revealed that participants fixated closer locations earlier than more distant locations. Importantly, this also held for 2D natural images. Taken together, we conclude that depth information changes basic eye movement properties and provides a salient image feature. <s> BIB001 </s> The Importance of Visual Attention in Improving the 3D-TV Viewing Experience: Overview and New Perspectives <s> B. Studies of Visual Attention in Stereoscopic Content <s> This poster will analyze the feasibility of eye tracking as a tool for helping filmmakers to make decisions in a stereoscopic film production. In a conventional dialogue driven shot it is fairly easy to predict where the audiences would be looking. However, for visually complex shots it is not so obvious. In this case, eye tracking can be used as a tool to observe the gaze pattern of the audience to identify the regions of interest in the frame. This information could be used to budget the resources for the shot. It can also be used to identify elements that distract the audience from the flow of the movie. This technique could be used to help filmmakers to make more informed decisions during the film making process. We analyzed a student produced stereoscopic film using this technique. In our study, a number of subjects were asked to watch the film and their gaze data was recorded. <s> BIB002 </s> The Importance of Visual Attention in Improving the 3D-TV Viewing Experience: Overview and New Perspectives <s> B. Studies of Visual Attention in Stereoscopic Content <s> We measured the eye movements of participants who watched a 6-minute movie in stereoscopic and non-stereoscopic ::: form. We analyzed four shots of the movie. The results indicate that in a 2D movie viewers tended to look at the actors, ::: as most of the eye movements were clustered there. The significance of the actors started at the beginning of a shot, as ::: the eyes of the viewer focused almost immediately to them. In S3D movie the eye movement patterns were more widely ::: distributed to other targets. For example, complex stereoscopic structures and objects nearer than the actor captured the ::: interest and eye movements of the participants. Also, the tendency to first look at the actors was diminished in the S3D ::: shots. The results suggests that in a S3D movie there are more eye movements which are directed to wider array of objects ::: than in a 2D movie. <s> BIB003 </s> The Importance of Visual Attention in Improving the 3D-TV Viewing Experience: Overview and New Perspectives <s> B. Studies of Visual Attention in Stereoscopic Content <s> Recent advances in video technology and digital cinema have made it possible to produce entertaining 3D stereoscopic ::: content that can be viewed for an extended duration without necessarily causing extreme fatigue, visual strain and ::: discomfort. Viewers focus naturally their attention on specific areas of interest in their visual field. Visual attention is an ::: important aspect of perception and its understanding is therefore an important aspect for the creation of 3D stereoscopic ::: content. Most of the studies on visual attention have focused on the case of still images or 2D video. Only a very few ::: studies have investigated eye movement patterns in 3D stereoscopic moving sequences, and how these may differ from ::: viewing 2D video content. In this paper, we present and discuss the results of a subjective experiment that we conducted ::: using an eye-tracking apparatus to record observers' gaze patterns. Participants were asked to watch the same set of ::: video clips in a free-viewing task. Each clip was shown in a 3D stereoscopic version and 2D version. Our results indicate ::: that the extent of areas of interests is not necessarily wider in 3D. We found a very strong content dependency in the ::: difference of density and locations of fixations between 2D and 3D stereoscopic content. However, we found that ::: saccades were overall faster and that fixation durations were overall lower when observers viewed the 3D stereoscopic ::: version. <s> BIB004
Although depth perception is possible with monoscopic images containing monocular depth cues, stereoscopic content brings important additional binocular cues enhancing our depth perception. A few studies have started to examine how visual attention may be influenced by such binocular depth cues. Jansen et al. examined the influence of disparity on human behavior in visual inspection of 2D and 3D still images BIB001 . They recorded binocular data in a free-viewing task on 2D and 3D versions of natural, pink noise, and white noise images. Although eye position data were collected binocularly, analysis was performed using only the data from the left eye. The argument to use only data from the left eye was that the input to the left eye was identical over 2D and 3D versions of the stimuli, as the 2D version of the 3D image consisted of two copies of the left view. In order to investigate the role of disparity as a bottom-up process of visual attention, they selected visual stimuli showing only natural landscapes without any man-made objects. They investigated the saliency of several image features: mean luminance, luminance contrast, texture contrast, mean disparity (used as a measure for distance), and disparity contrast (used as a measure for depth discontinuity). The additional depth information led to an increased number of fixations, shorter and faster saccades, and increased spatial extent of exploration. The saliency of mean luminance, luminance contrast, and texture contrast was comparable in 2D and 3D stimuli. Mean disparity was found to have a time-dependent effect in 3D stimuli. Disparity contrast was found to be elevated only at fixated regions in 3D noise images but not in 3D natural images. They observed that participants fixated closer locations earlier than more distant locations in the image. Interestingly, they also found the same behavior in 2D images where depth perception was provided by monocular cues. The study by Jansen et al. has shown that different depth cues have an influence on saccades. Based on these findings, Wismeijer et al. investigated if saccades are aligned with individual depth cues, or with a combination of depth cues  . In their experimental work, they presented subjects with surfaces inclined in depth, in which monocular perspective cues and binocular disparity cues specified different plane orientations, with different degrees of both small and large conflict between the two sets of cues. Additionally to recording eye movements, they asked participants to report their perception of plane orientation for each stimulus. They found that distributions of spontaneous saccade directions followed the same pattern of depth cue combination as perceived surface orientation: a weighted linear combination of cues for small conflicts, and cue dominance for large conflicts. They also examined the relationship between vergence and depth cues, and found that vergence is dominated only by binocular disparity. Häkkinen et al. examined how stereoscopic presentation can affect eye movement patterns by presenting the 2D and 3D versions of the same video content BIB003 . Their results indicated that eye movements for 3D content are more widely distributed. They reported that observers did not only look at the main actors in the movie but eye movements were also distributed to include other targets. Their observations therefore corroborate those from Jansen et al. The study by Häkkinen et al. provided some interesting insights on the influence of the presentation of stereoscopic content on visual attention, showing that differences exist between 2D and 3D content. However in this study, eye movements and scan paths were only analyzed and discussed in the 2D sense by looking at the spatial spread of eye fixations in the image, without considering those aspects in terms of the gaze depth. Furthermore, in this study, participants were instructed to compare the two versions (2D vs. 3D) and to provide their opinion on which version they thought was better. It can be argued that this experiment was therefore driven by a quality judgment task and therefore involved top-down aspects of visual attention. As part of a study related to stereo-filmmaking, Ramasamy et al. BIB002 found that, in a scene showing a long deep hallway, gaze points were more spread in the non-stereoscopic version than the stereoscopic version as gaze points were more concentrated at the far end (in terms of depth) of the scene in the stereoscopic version. In other words, these results indicate that the spread of fixations could be more confined when viewing 3D stereoscopic content, and oppose the conclusions by Jansen et al. BIB001 and Häkkinen et al. BIB003 . A recent work has also examined the differences in visual attention between the viewing of 2D and 3D stereoscopic content BIB004 . In this study, twenty-one different video clips with a wide variety of spatio-temporal characteristics and range of disparity were shown to a panel of viewers in both their 2D and 3D stereoscopic version. Gaze locations were recorded using an eye-tracking equipment in a free-viewing task. Average saccade velocity was found to be higher when viewing 3D stereoscopic content, corroborating results from Jansen et al. BIB001 who used still images. However, other results in BIB004 did not corroborate those reported by Jansen et al., as average fixation frequency and average fixation duration were found to be lower when viewing 3D stereoscopic content. Furthermore, the ob-servations reported in BIB004 did not show evidence that fixations were more widespread when viewing 3D stereoscopic content, nor the opposite. The spread of fixations was found to be highly dependent on the content characteristics and narrative flow of the video, and not only on the depth effect provided by the binocular disparity. In a video with a single scene and static camera view, allowing viewers more time to explore different areas in the scene, fixations were more widespread in 3D than in 2D, suggesting that viewers do explore more the scene in that case. On the other hand, in a video with fast motion and many rapid scene changes, the spatial locations and densities of the fixations were very similar in both cases and often biased toward the center of the image. It was also found that specific content features carrying high cognitive information, such as text and faces, clearly attracted viewers' attention and therefore produced similar fixation patterns, regardless of the (2D or 3D stereoscopic) version. Nonetheless, differences in gaze patterns were found. Some background areas that did not clearly attract attention in 2D became in some cases areas of interest in 3D, especially in content providing sufficient time for viewers to explore the scene. Finally, the authors found that, even if fixation locations were similar in the viewing of 2D and 3D stereoscopic content, the temporal order of the fixated locations presented differences. From the review of the different works above, we can conclude that the influence of the binocular depth cue on visual attention is highly dependent on the content itself and not only on the presence or strength of the disparity.