Stereoscopic Cues Research Articles

The interconnection of binaural and stereoscopic cues for distance perception

Encountering objects within our three-dimensional environment is a combination of sensory cues. While much research has been conducted on how the auditory and visual systems singularly locate objects in space, studies in cross-modal interaction of these two systems suggest the overall perception of a stimulus cannot fully be described by a single sensory system. The purpose of this study was to examine the relationship between visual and acoustic cues specifically in understanding depth perception. Previous studies of audio-visual interaction of spatial perception have accounted for many different auditory depth cues, but have not fully cross examined a number of visual depth cues. Participants were asked to determine the egocentric distance of a stimulus in a virtual three dimensional environment in terms of real-size quantitative scale. Stimuli were presented as either audio only, visual only, or audio and visual. The single-modal and multi-modal results were analyzed and compared against the null hypothesis that when presented simultaneously, the visual depth cues dominate the distance judgment and the acoustic depth cues have no bearing. In this study, the null hypothesis was not rejected, in accord with previous research investigating the proximity image effect.

Simulation of Driving in Low-Visibility Conditions: Does Stereopsis Improve Speed Perception?

Laboratory-based studies of perceived speed show that, under most circumstances, perceived speed is reduced as a function of contrast. However, a recent investigation of perceived vehicular speed while driving around a closed road circuit showed no such effect (Owens, Wood, & Carberry, 2010, Perception, 39: , 1199-1215). We sought to probe the source of this discrepancy, asking whether the presence or absence of stereoscopic motion information might account for the difference in results. In a two-alternative forced-choice psychophysical speed-discrimination task, observers compared the speed of high- and low-contrast driving clips filmed with a 3-D camera and presented either stereoscopically (3-D) or monoscopically (2-D). Although perceived speed was reduced at low contrast, the size of this misperception was equivalent for 2-D and 3-D presentations. However, the inclusion of stereoscopic cues to vehicular speed caused significant improvements in the precision of speed judgments. It is concluded that although stereopsis can provide access to valuable information on perceived speed, contrast-independent speed estimation as demonstrated by Owens et al. (2010) is more likely to reflect the use of the full visual field in a real driving situation (compared with limited field of view simulations), or the additional contributions of nonvisual cues rather than stereopsis.

The Effects of Stereoscopic Depth on Vigilance Task Performance and Cerebral Hemodynamics

The current study examined the effect of stereoscopic depth cues on vigilance performance and cerebral hemodynamics as reflected in cerebral bloodflow velocity (CBFV). During a 40 min continuous vigil, participants took the role of a flight engineer in a simulated fuel transfer task involving a circular gauge in which a vertical line was embedded. In a 2D condition, critical signals for detection were cases in which the vertical line was tilted slightly to the right. In a 3D condition, a stereoscopic display projected a 3D image in which critical signals were cases wherein the vertical line appeared to be located in front of the circular gage. The overall level of signal detections was greater in the 3D than in the 2D condition. Moreover, detection scores in the 2D condition showed the vigilance decrement, a temporal decline over time, while those in the 3D condition maintained relative stability. In both conditions, CBFV was greater in the right than in the left cerebral hemisphere and declined significantly over time. The results provide the the initial demonstration that 3D displays can enhance performance in tasks requiring sustained attention and that right hemispheric control may be involved in vigilance performance with both 2D and 3D stimuli.

Clinically Normal Stereopsis Does Not Ensure a Performance Benefit from Stereoscopic 3D Depth Cues

To investigate the effect of manipulating disparity on task performance and viewing comfort, twelve participants were tested on a virtual object precision placement task while viewing a stereoscopic 3D (S3D) display. All participants had normal or corrected-to-normal visual acuity, passed the Titmus stereovision clinical test, and demonstrated normal binocular function, including phorias and binocular fusion ranges. Each participant completed six experimental sessions with different maximum binocular disparity limits. The results for ten of the twelve participants were generally as expected, demonstrating a large performance advantage when S3D cues were provided. The sessions with the larger disparity limits typically resulted in the best performance, and the sessions with no S3D cues the poorest performance. However, one participant demonstrated poorer performance in sessions with smaller disparity limits but improved performance in sessions with the larger disparity limits. Another participant's performance declined whenever any S3D cues were provided. Follow-up testing suggested that the phenomenon of pseudo-stereoanomaly may account for one viewer's atypical performance, while the phenomenon of stereoanomaly might account for the other. Overall, the results demonstrate that a subset of viewers with clinically normal binocular and stereoscopic vision may have difficulty performing depth-related tasks on S3D displays. The possibility of the vergence---accommodation conflict contributing to individual performance differences is also discussed.

Differences between the Actual Scene Model and the Image Model for Computation of Visual Depth Information of Early Vision

In this paper, we introduced two viewing modes, "Scene Mode" and "Picture Mode", for early visual depth perception depending on the dimensions of the object being viewed. The essential difference between these two modes of visual depth perception is still unclear. We discuss the basic methods of introducing a three-dimensional Cartesian system into a plane to express the depth information of an image, estimate the loss of depth information caused by this approach, and provide an analysis of the important role of providing depth information based on size constancy and vanishing point in the two viewing modes. We studied the problem of how the retina and visual cortex separate the plenoptic (all-optical) function, which is the input representation of vision, by neural computing in scene mode. We also studied the problem of how to extract information about the position and angle of light beams in the light field, and then determined the output representation of the visual depth perception. In the absence of any stereoscopic cues, such as texture, gradient, shade, shadow, color, occlusion, and binocular disparity, we compare the main differences of visual depth perception between scene mode and picture mode using a cube being viewed and its line drawing, which respectively represent the two modes.

Measuring Sensitivity to Viewpoint Change with and without Stereoscopic Cues

The speed and accuracy of object recognition is compromised by a change in viewpoint; demonstrating that human observers are sensitive to this transformation. Here we discuss a novel method for simulating the appearance of an object that has undergone a rotation-in-depth, and include an exposition of the differences between perspective and orthographic projections. Next we describe a method by which human sensitivity to rotation-in-depth can be measured. Finally we discuss an apparatus for creating a vivid percept of a 3-dimensional rotation-in-depth; the Wheatstone Eight Mirror Stereoscope. By doing so, we reveal a means by which to evaluate the role of stereoscopic cues in the discrimination of viewpoint rotated shapes and objects.

Measuring Sensitivity to Viewpoint Change with and without Stereoscopic Cues

Measuring Sensitivity to Viewpoint Change with and without Stereoscopic Cues

Stereoscopy benefits processing of dynamic visual scenes by disambiguating object occlusions

How and to what extent stereoscopic cues help process dynamic visual scenes is still unknown. As we navigate in crowds or when we play sports we are often obliged to make rapid decisions in complex motion environments while attending to multiple elements. Stereoscopy can improve speed thresholds for a multiple object tracking (MOT) (Faubert & Sidebottom, 2012), but the nature of this advantage remains undetermined. From an attention perspective, there are at least two possible hypotheses to explain this advantage. One possibility is that stereoscopy reduces the attentional bottleneck as seen in 2-dimensional MOT environments (Intrilligator & Canavagh, 2001) by distributing attention uniformly in 3D space. Another hypothesis is that the stereoscopy helps attentional tracking by segregating the target and the non-target objects during occlusions. We have addressed these hypotheses by testing subjects with and without stereoscopic cues for different stimulus configurations in which pairs of spheres were rotating in orbit with one another in a 3D virtual space. In one set of conditions, object pairs rotated without ever occluding each other. In the second set of conditions, the objects occasionally occluded each other as they were rotating around an axis perpendicular to the observer. All conditions consisted of 4 pairs of spheres presented in each quadrant of the visual field at 20 degrees of eccentricity. Stereoscopy improved MOT speed threshold by a factor of about 3 when objects occluded each other, but slightly, yet significantly, impaired speed threshold by about 18% when objects did not occlude each other. We conclude that the overall benefit of stereoscopy for processing dynamic scenes comes from improved attention tracking by disambiguating targets from non-targets during occlusions. Conversely, stereoscopic cues were a disadvantage in absence of occlusions. Meeting abstract presented at VSS 2013

Discrimination of rotated-in-depth curves is facilitated by stereoscopic cues, but curvature is not tuned for stereoscopic rotation-in-depth

Object recognition suffers when objects are rotated-in-depth, as for example with changes to viewing angle. However the loss of recognition can be mitigated by stereoscopic cues, suggesting that object coding is not strictly two-dimensional. Here we consider whether the encoding of rotation-in-depth (RID) of a simple curve is tuned for stereoscopic depth. Experiment 1 first determined that test subjects were sensitive to changes in stereoscopic RID, by showing that stereoscopic cues improved the discrimination of RID when other spatial cues to RID were ineffective. Experiment 2 tested directly whether curvature-sensitive mechanisms were selective for stereoscopic RID. Curvature after-effects were measured for unrotated test curves following adaptation to various RID adaptors. Although strong adaptation tuning for RID angle was found, tuning was identical for stereo and non-stereo adaptors. These findings show that while stereoscopic cues can facilitate three-dimensional curvature discrimination, curvature-sensitive mechanisms are not tuned for stereoscopic RID.

Stereoscopic Depth Cues Outperform Monocular Ones on Autostereoscopic Display

The aim of this study is two-fold; first, to compare how certain visual aids contribute in depth estimation tasks on a portable autostereoscopic display; and second, how these depth cues impact on perceived quality. These were studied on a quantitative subjective study using a portable autostereoscopic display in controlled laboratory environment. Test participants evaluated object depths on three-dimensional images, where either 2D cues, 3D cues, or their combinations were provided. The study was conducted using three different compression levels in order to study how image quality affects the perception of depth. The results indicate that the depth estimation task is faster conducted when the participants relied on stereoscopic depth cues compared to situations where only monocular cues were present. Also, depth estimation task is faster conducted with higher quality images. Depth estimation accuracy was also higher with stereoscopic depth cues than with monocular ones. These results suggest that the human visual system can make more reliable depth estimates on portable autostereoscopic displays when stereoscopic cues are present. However, the results of the quality evaluations indicate that, as stated also on previous studies, the added stereoscopic depth does not seem to increase the subjective image quality.

The role of stereoscopic depth cues in shape constancy

The role of stereoscopic depth cues in shape constancy

Evaluating 2D and 3D geovisualisations for basic spatial assessment

This study investigates the use of 2D and 3D presentations of maps for the assessment of distances in a geographical context. Different types of 3D representations have been studied: A weak 3D visualisation that provides static monocular depth cues and a strong 3D visualisation that uses stereoscopic and kinetic depth cues. Two controlled experiments were conducted to test hypotheses regarding subjects’ efficiency in visually identifying the shortest distance among a set of market locations in a map. As a general result, we found that participants were able to correctly identify shortest distances when the difference to potential alternatives was sufficiently large, but performance decreased systematically when this difference decreased. Noticeable differences emerged for the investigated visualisation conditions. Participants in this study were equally efficient when using a weak 3D representation and a 2D representation. When the strong 3D visualisation was employed, they reported visual discomfort and tasks solved were significantly less correct. Presentations of intrinsic 2D content (maps) in 3D context did not, in this study, benefit from cues provided by a strong 3D visualisation and are adequately implemented using a weak 3D visualisation.

Multisensory interactions modulate response of V3A for depth-motion processing

For the perception of an object moving in depth, stereoscopic signals provide us with an important spatial cue. However, other modalities can also contribute to the motion perception. For example, auditory signals generated by the moving object change according to the approaching/receding direction. Specifically, sound intensity increases/decreases, while sound frequency shifts to higher/lower frequencies (i.e., the Doppler effect). The integration of these unisensory cues may enhance the perception of motion direction by modulating activity within specific brain areas. This fMRI study assessed the interaction between auditory and visual depth-cues on the response of V3A. The task was to discriminate the direction of an auditory target that moved in depth without any azimuth shift. Orthogonally to the volume change, the sound frequency could either rise or fall, yielding to Doppler ‘matched vs. unmatched’ conditions. On two-thirds of the trials, the sound was synchronously coupled with a task-irrelevant visual stimulus moving either forward or backward (i.e., a ball expanding or contracting), thus leading to audio–visual ‘congruent vs. incongruent’ signals of motion. These conditions were presented either in ‘2D or 3D’ viewing. The behavioral data showed the best motion-direction discrimination performance was obtained in Doppler matched and audio–visual congruent condition. In V3A, we found the expected responses to stereoscopic cues and, most importantly, maximal activation was found for 3D trials comprising matched Doppler and congruent audio–visual signals. These results demonstrate that the perception of objects moving in depth entails the integration of multiple unisensory cues. These support that the integration can affect activity in brain regions traditionally considered as unimodal.

Enhancement of three-dimensional perception of numerical hologram reconstructions of real-world objects by motion and stereo

We investigated the question of how the perception of three-dimensional information reconstructed numerically from digital holograms of real-world objects, and presented on conventional displays, depends on motion and stereoscopic presentation. Perceived depth in an adjustable random pattern stereogram was matched to the depth in hologram reconstructions. The objects in holograms were a microscopic biological cell and a macroscopic metal coil. For control, we used real physical objects in additional to hologram reconstructions of real objects. Stereoscopic presentation increased perceived depth substantially in comparison to non-stereoscopic presentation. When stereoscopic cues were weak or absent e.g. because of blur, motion increased perceived depth considerably. However, when stereoscopic cues were strong, the effect of motion was small. In conclusion, for the maximization of perceived three-dimensional information of holograms on conventional displays, it seems highly beneficial to use the combination of motion and stereoscopic presentation.

Investigating the performance of path-searching tasks in depth on multiview displays

Multiview auto-stereoscopic displays support both stereopsis and head motion parallax depth cues and could be superior for certain tasks. Previous work suggests that a high viewpoint density (100 views/10cm at the eye) is required to convincingly support motion parallax. However, it remains unclear how viewpoint density affects task performance, and this factor is critical in determining display and system design requirements. Therefore, we present a simulated multiview display apparatus to undertake experiments using a path-searching task in which we control two independent variables: the stereoscopic depth and the viewpoint density. In the first experiment, we varied both cues and found that even small amounts of stereo depth (2cm) reliably improved task accuracy and reduced latency, whereas there was no evidence of dependence on viewpoint density. In the second experiment, we switched off the stereoscopic cue and varied viewpoint density alone. We found that for these monoscopic images increasing viewpoint density resulted in some reduction in response latency (up to eight views/10cm) but had no effect on accuracy. We conclude for cases where occlusion is not an overriding factor that low viewpoint densities may be sufficient to enable effective path-searching task performance.

Inferring Cross-Sections: When Internal Visualizations Are More Important Than Properties of External Visualizations

Three experiments examined how cognitive abilities and qualities of external visualizations affected performance of a mental visualization task; inferring the cross-section of a complex three-dimensional object. Experiment 1 investigated the effect of animations designed to provide different task-relevant views of the external object. Experiment 2 examined the effects of both stereoscopic and motion-based depth cues. Experiment 3 examined the effects of interactive animations, with and without stereoscopic viewing conditions. In all experiments, spatial and general reasoning abilities were measured. Effects of animation, stereopsis, and interactivity were relatively small and did not reach statistical significance. In contrast, spatial ability was significantly associated with superior performance in all experiments, and this remained true after controlling for general intelligence. The results indicate that difficulties in this task stem more from the cognitive ability to perform the relevant internal spatial transformations, than limited visual information about the three-dimensional structure of the object.

Are stereoscopic cues ignored in telestereoscopic viewing?

Are stereoscopic cues ignored in telestereoscopic viewing?

Combination of stereoscopic and monocular form cues in cells of monkey area V2

Combination of stereoscopic and monocular form cues in cells of monkey area V2

Adapting internal statistical models for interpreting visual cues to depth

The informativeness of sensory cues depends critically on statistical regularities in the environment. However, statistical regularities vary between different object categories and environments. We asked whether and how the brain changes the prior assumptions about scene statistics used to interpret visual depth cues when stimulus statistics change. Subjects judged the slants of stereoscopically presented figures by adjusting a virtual probe perpendicular to the surface. In addition to stereoscopic disparities, the aspect ratio of the stimulus in the image provided a "figural compression" cue to slant, whose reliability depends on the distribution of aspect ratios in the world. As we manipulated this distribution from regular to random and back again, subjects' reliance on the compression cue relative to stereoscopic cues changed accordingly. When we randomly interleaved stimuli from shape categories (ellipses and diamonds) with different statistics, subjects gave less weight to the compression cue for figures from the category with more random aspect ratios. Our results demonstrate that relative cue weights vary rapidly as a function of recently experienced stimulus statistics and that the brain can use different statistical models for different object categories. We show that subjects' behavior is consistent with that of a broad class of Bayesian learning models.

Visual Perception: Converging Mechanisms of Attention, Binding, and Segmentation?

Visual scenes are cluttered. Recent evidence suggests that areas as early as V1 and V2 help making sense of the scene by segmenting them into distinct objects, separating foreground and background, and binding features.