2) We train a visual comfort prediction function, and
distinguish a stereoscopic image as high comfortable
stereo viewing (HCSV) or low comfortable stereo view-
ing (LCSV) and then derive different visual comfort
based saliency maps for these two cases.
3) Factors from low-level visual features, depth perception
and visual discomfort, are considered to derive 2D
saliency, depth saliency and visual comfort based
saliency, receptively, and three saliency maps are inte-
grated into a 3D saliency map.
The remainder of this paper is organized as follows.
Section 2 analyzes the relationship between visual dis-
comfort and 3D visual attention. Section 3 illustrates each
part of the proposed 3D saliency computational model in
detail. Experimental results are given in Sections 4 and 5
drawn conclusions of this paper.
2. Relationship between visual discomfort and 3D visual
attention
As introduced in Section 1, there are numerous potential
causes of visual discomfort when viewing 3D images such as
conv erg enc e–accommodation conflict,binocularmismatch,
crosstalk, dep th motion, unnatural blur/sharpness, etc. In this
paper, we focus on the converg ence-ac commodati on conflict,
because it is present in all disparity-based stereo displays,
while the other factors are not present in some instantiations
of st er eo display technolo gy [42].
Fig. 1 shows the accommodation and convergence differ-
ences under natural viewing and stereo viewing. In natural
viewing, the view er adjusts the vergence of the eyes t o look at
an object, and the accommodation and convergence are
alway s coupled. While in the stereo viewing, the convergence
distance is unconsciously adjusted accor ding to the depth
position of the perceived object, which may be located behind
or in front of the screen, while the accommodation still
remains on the screen.
From the perspective of neural processing, the conflict
induced by stereo viewing need to be resolved: the viewer
must accommodate to a different distance than the dis-
tance to which he/she must converge, because of the
neural coupling mechanism between convergence and
accommodation. Otherwise, symptoms like eyestrain,
headache, visual discomfort, and diplopia phenomenon
may occur. However, previous studies have investigated
that objects could be seen clearly while maintaining
binocular fusion when they are positioned inside a specific
area. This specific area is known as Zone of Clear Single
Binocular Vision (ZCSBV) [52]. In addition, the set of
accommodation and convergence responses that can be
achieved without discomfort is defined as Percival's Zone
of Comfort (PZC), which is about one-third of ZCSBV
[53,54]. Obviously, objects in the natural viewing always
fall inside the PZC while many perceived objects under 3D
viewing do not. Fig. 1(b) and (c) shows the cases that the
perceived object falls inside and outside the PZC, respec-
tively. To fuse and focus the 3D objects that perceived
outside the PZC, the viewer must struggle to counteract
the normal accommodation–convergence coupling, lead-
ing to visual discomfort [55]. Therefore, from the perspec-
tive of providing high QoE to viewers, salient objects
should be positioned inside the PZC (small disparity) to
reduce the conflict between accommodation and conver-
gence whenever possible (This motivates us to consider
small disparity as a rule to predict salient locations in
perceptually comfortable stereoscopic images).
From another perspective, it is generally accepted that
people are usually interested in the regions popping out
from the screen, which may have small depth (or large
disparity) values against the other regions [56]. These
popping-out regions will automatically attract more atten-
tion no matter whether the stereoscopic image is percep-
tually comfortable or not. Motivated by this property,
regions with large disparity tend to be salient for comfor-
table or uncomfortable stereoscopic images. However, this
property seems to be completely contradictory to the
previous discussed property that the salient objects will
be designated small disparities to provide high visual
comfort. In order to distinguish the above two properties
Fig. 1. Illustrations of different manifestations of accommodation and convergence under natural viewing and stereo viewing. (a) Natural viewing; (b) high
comfortable stereo viewing (the perceived object falls inside the PZC); (c) low comfortable stereo viewing (the perceived object falls outside the PZC).
Please cite this article as: Q. Jiang, et al., A depth perception and visual comfort guided computational model for
stereoscopic 3D visual saliency, Signal Processing-Image Communication (2015), http://dx.doi.org/10.1016/j.
image.2015.04.007i
Q. Jiang et al. / Signal Processing: Image Communication ] (]]]]) ]]]–]]] 3