Stereokinetic Effect Research Articles

Monocular Depth Estimation (Literature Review)

Background. The physiological basis of spatial perception is traditionally attributed to the binocular system, which integrates the signals coming to the brain from each eye into a single image of the three-dimensional outside world. The perception of three-dimensionality, however, is also possible due to the evolutionarily older monocular system of spatial perception. Normally, the binocular mechanism plays the leading role in depth perception, and its violations lead to a shift towards the monocular. In this regard, one of the relevant areas of ophthalmology and neurophysiology is the study of the features of monocular depth estimation in normal conditions and cases of ophthalmic pathology.Purpose: to study the literature data on the monocular depth estimation mechanism, methods of its assessment, as well as the peculiarities of its manifestations in normal conditions and cases of ophthalmic pathology.Materials and methods. The literature analysis of publications on PubMed, eLibrary, Cyberleninka and crossref metadata search was carried out.Results. The review considers modern ideas regarding monocular depth cues that can ensure the effective operation of the monocular mechanism of spatial vision. The stereokinetic effect (SE) is considered in detail. The possibilities of using SE assessment methods to evaluate the state of spatial vision mechanisms in cases of ophthalmic and neurological pathology have been studied.Conclusion. There are a number of monocular depth cues that can ensure the effective operation of the monocular mechanism of spatial vision, such as: perspective, light and color effects, accommodation and knowledge of the true sizes of the objects acquired with experience. Stereokinetic effect caused by the successive displacement of projections of circular eccentric images on the retina, which allows to evaluate relationship of monocular and binocular mechanisms of spatial perception, has a particular importance for ophthalmology practice. In patients with binocular vision disorders (amblyopia and strabismus), a decrease in monocular and an increase in binocular SE indicators were observed, whereas only a decrease in monocular indicators is more typical for organic ocular fundus pathology. At the same time, changes in SE indicators can serve as additional criteria for evaluating the efficacy of functional treatment of binocular disorders.

Взаимоотношения монокулярного и бинокулярного механизмов пространственного восприятия до и после функционального лечения у детей с послеоперационной остаточной микродевиацией

Purpose. Of this work is to study the relationship of monocular and binocular mechanisms of spatial perception before and after functional treatment in children with postoperative residual microdeviation. Material and methods. The study included 30 children aged 8 to 16 years (average 12.5 years) with postoperative residual microdeviation (RM) and 44 children of the same age (average 10.6 years) in the control group. Along with the usual ophthalmic examination, Bagolini test, Lang test and Fly test were used to evaluate binocular functions in all children. To study the stereokinetic effect (SE), a ring image with a diameter of 20 cm with an eccentricity (the ratio of the displacement of the central element of the ring image from the center of rotation to the radius of the image) of 0.4 rotating on a laptop screen at the speed of 60 rpm was presented using a computer program developed by M.V. Zhmurov was used. The distance from the eyes to the image was 3 m. A child was asked to evaluate the illusory size of the virtual cone or the virtual funnel in binocular and monocular viewing conditions. Seven reference paper cones with a base diameter of 20 cm and a height of 5.10, 15, 20, 25, 30 and 35 cm were used to facilitate estimates of the SE value. The child pointed the paper cone closest in size to the virtual cone or virtual funnel. We also noted the time of dominance of the virtual cone and the virtual funnel during their alternation (in seconds per 1 min) and then calculated the average time of domination of both variants of the virtual figure. The study of visual functions and SE in children with RM was carried out before and after the course of functional treatment, providing presenting of stereostimules in the alternation mode using a computer program developed by M.V. Zhmurov. Three modes of alternative presentation of stimuli were used: 1) with consecutive monocular presentation of visual stimuli corresponding to the right and left eye; 2) with the presence of an empty interval between monocular phases; 3) with the presence of a binocular phase between monocular phases. Results. In all children with RM, the results of the stereovision study with Lang-test, Fly-test were negative before treatment. After functional treatment, 24 children showed stable binocular character of vision, the results of the study with Fly-test after treatment were positive in 20 children, and in five children with Lang-test. Orthotropy was achieved in 24 children. As a result of treatment, the visual acuity of the amblyopic eye increased from 0.74±0.03 to 0.91±0.01. The number of children with RM perceiving SE in the form of alternating virtual figures (cone and funnel) increases from 50% to 83.3% as a result of treatment. The dominance time of the virtual cone in children with RM significantly decreased (p<0.01) after treatment both in monocular conditions (average from 2.9±0.2 to 2.3±0.1 s) and in binocular conditions (average from 3.6 ±0.2 to 3±0.1 s), reaching the values of the control group. As a result of treatment of children with RM, the average size of the virtual cone for binocular conditions decreased from 21.3±1.2 to 16.8±0.9 cm and was significantly lower (p<0.001) compared with both the mean values before treatment and with the average values in the control group. After treatment, the average value of the virtual funnel for binocular conditions decreased from 19±1.1 cm to 13.1±0.7 cm and was significantly lower compared with the values obtained before treatment (p<0.001) and in the control group (p<0.05). Conclusion. Using alternating presentation of stereoimages in functional treatment of children with RM leads to positive changes: a reduction or elimination of residual deviation, improved visual acuity of amblyopic eye, increasing of the number of patients with stable bifoveal fusion and appearance of a stereo vision in them. The number of children with RM perceiving SE in the form of alternating virtual figures (cone and funnel) increases as a result of treatment. The dominance time of the virtual cone in children with RM significantly decreases after treatment, reaching the values in the control group. The average value of the virtual cone size for binocular conditions in children with RM significantly decreases after treatment to values smaller than in the control group, and for monocular observation conditions – increases to values comparable with the results in the control group. The average value of the virtual funnel size for binocular conditions in children with RM significantly decreases after treatment in comparison both with the values obtained before treatment and with the values obtained in the control group. Changes in the relationship between monocular and binocular mechanisms of spatial perception can serve as additional criteria for assessing the effectiveness of functional treatment of patients with RM.

Dependence of the Stereokinetic Effect on the Rotational Speed and Eccentricity of the Test Image in Children with Partial Optic Atrophy

We studied the influence of the rotational speed and eccentricity of the ring image on the severity of the stereokinetic effect (SE) in a group of 36 children aged 8 to 16 years with partial optic atrophy and in the control group of 44 age-matched children with a normal fundus. Four variants of the ring image with the eccentricity of 0.2, 0.4, 0.6 or 0.8 were used as a test image. The rotational speed of the ring image was 2, 10, 30, 60 or 90 rpm. It was found that the stereokinetic effect was absent in the majority of children (63.9%) with optic atrophy at a combination of eccentricity of 0.2 and a rotational speed of 2 rpm, in contrast to the control group, where the stereokinetic effect was only absent in 9.1% of children under the same conditions of stimulus presentation. The stereokinetic effect was observed with all eccentricities when the speed of rotation of the test image was 30–90 rpm in children with optic atrophy and 10–90 rpm in children from the control group. The number of children with alternate perception of the virtual cone and the virtual funnel was significantly higher in the control group than in the group of children with optic atrophy at all the test image eccentricities and rotational speeds used. The binocular figure size estimates were equal to the monocular estimates in the group of children with optic atrophy for all the image eccentricities and rotation speeds in contrast to the control group with a general tendency for the virtual cone size estimate to increase under the monocular conditions of observation. An increase in the test image rotation speed from 2 to 60 rpm was accompanied by an increase in the size of a virtual figure and a significant decrease in the duration of alternate dominance of virtual cone and virtual funnel perception in both groups of subjects with all the eccentricities used. The difference between the results obtained in the group of children with POA and in the control group may be explained by reduction of afferent visual information flow. These differences are partially offset by increased speed and increased eccentricity of the test image.

A computational explanation of the stereokinetic effect

A computational explanation of the stereokinetic effect

Perceptual elasticity in stereokinetic effect

Perceptual elasticity in stereokinetic effect

Neural correlates of the stereokinetic effect revealed by functional magnetic resonance imaging

The stereokinetic effect (SKE) refers to a visual phenomenon in which a two-dimensional figure rotating in the fronto-parallel plane about the visual axis can create the impression of a three-dimensional (3-D) object. Although several characteristics of SKE suggest that the perceptual mechanisms involved in SKE may differ from those of the kinetic depth effect (KDE), the differences between SKE and KDE in neural mechanisms have not yet been investigated. In order to determine the cortical areas involved in SKE, we presented a variety of SKE stimuli in a series of functional magnetic resonance imaging experiments, controlling for motion and contrast energies as well as stimulus presentation paradigm. Cortical activation associated with SKE was observed in the middle temporal complex (hMT+), lateral occipital area (LO), V3B, inferior temporal gyrus (ITG), fusiform gyrus (FG), and dorsal intraparietal sulcus anterior (DIPSA). On the other hand, ITG, FG, and DIPSA were also activated by the static versions of SKE stimuli. hMT+, LO, and V3B are also known to be activated in KDE. These findings suggest that general motion-dependent 3-D object processing may be performed in these areas.

Motion Minimization and the Stereokinetic Effect

Motion Minimization and the Stereokinetic Effect

Stereokinetic interaction effects involving static and slowly moving identical figures.

Here a new depth effect evoked by the spatial and temporal interaction in 2-D of a slowly moving circle (optimally at 0.6 rads/sec) with an identical static circle is reported. Typically, respondents report that with increasing adjacency, commencing with separations of a few diameters, the moving circle appears in a different plane of depth to the static circle, it then usually appears to "dip" onto the static circle and after complete coincidence with it to rise away from it. This effect, together with a number of associated descriptions are commented upon, in addition to observations when viewing overlapped static circles and overlapped circles in motion, this latter stimulus condition evoking the stereokinetic effect. The authors have previously suggested that contour "sliding," which simulates motion parallax, is the key to understanding stereokinesis. The stimulus conditions giving rise to this new effect directly simulate the motion parallax information present in a retinal image.

ドットパターンの偏心回転による錯視的三次元表面の成立

The stereo-kinetic phenomenon reported by Zanforlin, Vallortigara, and Agostini (1991) was observed under the condition of stroboscopic movement. On the CRT display, multiple eccentric circles, drawn by either line pattern or random dot pattern, were rotated. Observing these stimulus figures, the subjects reported the stereo-kinetic effect, namely they perceived clearly the solid cones rotating in depth. The subjects then were asked to judge the height of the perceived stereo-kinetic cones. The results showed that, despite the difference in pattern components, line or dot, the perceived stereo-kinetic cones were very similar in the appearance of their heights. However, the results revealed that the values of the apparent height did not accord with the formula proposed by Zanforlin et al. The findings in the present study were discussed in terms of a quantitative form of “structure from motion”

Stereokinetic effects with sharp and fuzzy illusory contours.

A black, 8-shaped pattern, whose centre of gravity is in the centre of a rotating disc, appears to split into two black discs rotating with phenomenal independent motion, orientation stability, and sliding of one on the other. The type of observed movement, the order of overlapping, and the extent of the stereokinetic depth in relation to the contour type and different dimensions of the pattern were investigated. The experimental data show that a fuzzy contour facilitates the stereokinetic effect. Furthermore, the extent of the stereokinetic depth has been found to be greater in case of fuzzy contour and vertical orientation of the pattern. These results are in contrast with the models in which this effect is considered as a problem of minimisation of distances or velocities. A vector model of the observed movement and an interpretation of the overlapping based on an energy approach are proposed. A tentative explanation of the stereokinetic depth for our patterns is put forward.

Analysis of two- and three-dimensional rigid and nonrigid motions in the stereokinetic effect

Continued viewing of a rotating ellipse induces three types of percept: the veridical percept (rigid, flat, rotating ellipse), the amoeboid percept (nonrigid, flat, deforming ellipse), and the stereokinetic percept (rigid circular disk rolling in three-dimensional space). A mathematical analysis of the nonveridical percepts is presented, based on the aperture problem and the assumption that the vector field N (the normal component of the rotational velocity field R of the ellipse) is the effective stimulus. Perceived nonrigidity of the amoeboid percept is assessed by an analysis of the geometrical nonrigidity of N. Two analytical tests of geometrical rigidity of velocity fields are described. The first is based on the decomposition of the velocity gradient matrix, and the second is based on an analysis of the temporal derivative of the curvature of moving plane curves. Both tests confirm the geometrical nonrigidity of N, on which the perceived nonrigidity might be based. A limitation of both approaches with respect to the analysis of shape-preserving nonrigidity is noted. For an understanding of the stereokinetic percept and its relation to N, a detailed kinematic analysis is presented of the type of motion that a real circular disk (the physical stereokinetic disk) would have to perform in order to duplicate the perceived motion of the perceptual stereokinetic disk induced by the rotating ellipse. The analysis is based on the Eulerian decomposition of rigid-body rotation into precession, nutation, and spin. It is concluded that the stereokinetic effect cannot be directly based on N because the projected velocity field of the physical stereo-kinetic disk, P differs from N. However, a subsequent transformation with N as the input vector field produces an output vector field whose structure is similar to P, except for scale. This transformation is based on the vector interaction algorithm, which is motivated by psychophysical data on contextual effects in the perception of motion direction. It is also demonstrated that this algorithm predicts qualitative aspects of percepts in several other relevant examples, such as the barber pole effect, translating nonoccluded line segments, and eccentrically rotating circles. An additional analysis shows that, although there is an infinity of figures projectively equivalent to a static ellipse, the added dynamical constraint of projective equivalence of the velocity vector field of a moving figure to P implies that the only rigid figure consistent with stimulation and processing conditions is a circular disk. The bases of the three types of percept induced by the rotating ellipse are assumed to be the neural counterparts of three vector fields: R N, and P.

Depth perception in motion parallax and stereokinesis.

Perceived depth in the stereokinetic effect (SKE) illusion and in the monocular derivation of depth from motion parallax were compared. Motion parallax gradients of velocity can be decomposed into 2 components: object- and observer-relative transformations. SKE displays present only the object-relative component. Observers were asked to estimate the magnitude and near-far order of depth in motion parallax and SKE displays. Monocular derivation of depth magnitude from motion parallax is fully accounted for by the perceptual response to the SKE, and observer-relative transformations absent in the SKE are of perceptual utility only as determinants of the near-far signing of perceived sequential depth. The amount of depth and rigidity perceived in motion parallax and SKE displays covaries with the projective size of the stimuli. The monocular derivation of depth from motion is mediated by a perceptual heuristic of which the SKE is symptomatic.

Using stereokinetic effect to convey depth: computationally efficient depth-from-motion displays.

Recent developments in microelectronics have encouraged the use of 3D data bases to create compelling volumetric renderings of graphical objects. However, even with the computational capabilities of current-generation graphical systems, real-time displays of such objects are difficult, particularly when dynamic spatial transformations are involved. In this paper we discuss a type of visual stimulus (the stereokinetic effect display) that is computationally far less complex than a true three-dimensional transformation but yields an equally compelling depth impression, often perceptually indiscriminable from the true spatial transformation. Several possible applications for this technique are discussed (e.g., animating contour maps and air traffic control displays so as to evoke accurate depth percepts).

Stereokinetic effect and its relation to the kinetic depth effect.

The stereokinetic effect (SKE) has been defined and studied by nested circular patterns rotating on a turntable. Circles must appear not to rotate as they revolve, which in turn results in their appearing to translate relative to one another. A powerful illusion of object depth results even though the individual circles do not undergo an appropriate foreshortening consistent with their apparent changes in slant. It is suggested and tested that the SKE is based on the changing positions between the nested contours despite the absence of any change within each contour, whereas the kinetic depth effect (KDE) entails both kinds of change. It follows that a turntable method of presentation is not necessary, and between-contour transformations can be simulated by computer animation. Displays consisting of simple translations were shown to evoke robust depth impressions as were patterns consisting of contours of varying shapes. Comparisons of the depth, compellingness, and rigidity of matched SKE and KDE displays are reported. The SKE is taken to be paradigmatic for how the visual system perceives depth when observing small object rotations that occur in everyday situations.

Stereokinetic effect and its relation to the kinetic depth effect.

Stereokinetic effect and its relation to the kinetic depth effect.

Identity imposition and its role in a stereokinetic effect

Lines of constant curvature, a circle or a straight line, have no distinguishable parts. Yet they are perceived as if they did. When they move and intersect, they are perceived to slide across each other as if one of them had parts that can be seen to move in relation to the other line. With no such parts present in stimulation, they are products of perception. It was found that a third line of constant curvature, the helix, is also seen to slide when two helixes intersect and are in motion. Another manifestation of perceived identical parts is that rotating circles and similar shapes are perceived not to rotate even when cues for rotation are present. Furthermore, changes between merely perceived identical parts can result in apparent depth. Evidence is presented that such depth, known as the stereokinetic effect, results from kinetic depth-effects that are based on perceived identical parts instead of on actually identical parts, and that depth is seen when the intervals between such perceived parts change length and orientation simultaneously.

Learning to see stereokinetic effects.

The Saturn illusion is a stereokinetic effect that occurs when a flat pattern composed of a full ellipse with two symmetrical semirings is rotated slowly in the frontoparallel plane. Subjects report seeing an egg-shaped object inserted into a circular ring, and the two objects move solidly into 3-D space as a single rigid body. Inexperienced observers show a conspicuous delay before reaching this percept. Two experiments are reported in which it is shown that this incubation time progressively decreases with repeated exposures to the stimulus pattern. A certain amount of time (14 s on average) is, however, required to obtain the effect, even after six successive exposures. It is argued that this time, which is independent of the speed of rotation and is not further reducible, is a fixed entity and is needed to compute the most rigid 3-D solution from deformations in the 2-D image. The results are discussed in relation to current theories of perception of structure from motion.

Multiple 3-D interpretations in a classic stereokinetic effect.

It is known that a flat ellipse rotating in the frontoparallel plane sooner or later appears as a rigid circular disc tilting in 3-D space. An experiment is reported in which prolonged exposure to the same flat pattern produces a second previously unnoticed 3-D percept: an elongated egg slanted in 3-D space, which points towards the observer and the end parts of which describe a circular trajectory in the frontal plane. It is shown that the achievement of this alternative percept is not affected by the particular shape of the ellipse, although the time needed to reach it increases with an ellipse with a 2:3 axis ratio.

The saturn illusion: A new stereokinetic effect

When a 2-D pattern composed of a solid ellipse with two symmetrical semi-rings (corresponding to the visible parts of a contour ellipse whose major axis is perpendicular to that of the solid ellipse) is slowly rotated about an axis coincident with the line of sight, a compelling 3-dimensional impression occurs. Subjects report seeing an egg-shaped object which is inserted into a circular ring: the two objects move solidly into 3-D space and a moving visual phantom is generated so that the ring appears completed by an illusory curved segment in the region nearer to the observer during rotation. A sequence of nonrigid and rigid percepts (both 2-D and 3-D) precedes this Saturn-like configuration.

Wobble cones and wobble holes: the stereokinetic effect revisited.

It is well-known that patterns of eccentric circles when slowly rotated give rise to compelling three-dimensional impressions of cones or conical holes which can 'wobble' as the pattern rotates. The wobble can be considered as part of the overall phenomenon of depth elicited from a rotating display, the 'stereokinetic' effect (SKE). This paper considers the three-dimensional appearance as being the result of the sliding of contours and thus it imitates the motion parallax found in real three-dimensional objects in motion. New variants of SK figures are used to examine these points. An analogy with computer programs is proposed which questions earlier views on the location of perceptual invariance.