Occlusion Constraints and Stereoscopic Slant

Perception ◽  
1997 ◽  
Vol 26 (1) ◽  
pp. 29-38 ◽  
Author(s):  
Jukka Häkkinen ◽  
Göte Nyman
Keyword(s):  
Binocular Vision ◽  
Retinal Image ◽  
Three Dimensional ◽  
Vertical Axis ◽  
The Other ◽  
Necessary Condition ◽  
Slant Perception ◽  
Frontoparallel Plane ◽  
Reduction Effect

In binocular vision horizontal magnification of one retinal image leads to a percept of three-dimensional slant around a vertical axis. It is demonstrated that the perception of slant is diminished when an occlusion interpretation is possible. A frontoparallel plane located in the immediate vicinity of a slanted surface in a location which allows a perception of occlusion reduces the magnitude of perceived slant significantly. When the same plane is placed on the other side, the slant perception is normal because there is no alternative occlusion interpretation. The results indicate that a common border between the occluder and a slanted surface is not a necessary condition for the reduction effect. If the edges are displaced and the edge of the slanted surface is placed in a location in which it could be occluded, the effect still appears.

Measurement of the Shortening Effect on the Perceived Path of Stroboscopic Movement

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 288-288
Author(s):  
S Nozawa
Keyword(s):  
Three Dimensional ◽  
Vertical Axis ◽  
Horizontal Axis ◽  
The Other ◽  
Horizontal Line ◽  
Optimal Frequency ◽  
Stimulus Line ◽  
Factors Influencing ◽  
Parallel Motion ◽  
Axis I

When two vertical short lines are alternately flashed at certain SOAs, a shortening of the apparent path of the stroboscopic movement is perceived. In the experiments reported here, factors influencing the shortening effect were studied with lines created on a CRT display. Experiment 1 was designed to study the effect of SOA. Each stimulus line was always presented for 100 ms, but intervals were varied in the range from 25 to 800 ms. With short and long SOAs almost no shortening illusion was observed, whereas the SOA for optimal stroboscopic motion (200 ms) also produced the largest illusion (ca 16%). This agrees with the classic study by Scholz (1924 Psychologische Forschung5 219 – 272) who found the largest illusion (25%) at the optimal frequency for stroboscopic motion. Experiment 2 dealt with the effect of inversions (I), mirror reflections (M), and rotations (R) of the line during the stroboscopic movement (see Kolars and Pomerantz, 1971 Journal of Experimental Psychology87 99 – 108). The particular movements were signalled by means of a short horizontal line added to one end of each of the two vertical lines of experiment 1. The configurations were (1), signifying parallel motion in one plane; (2), locomotion with rotation around the vertical axis (M); (3), locomotion with rotation around the horizontal axis (I); and (4), locomotion with rotation in the plane of the display (R). In all these conditions, the shortening illusion was significantly larger than in experiment 1. The differences between the four conditions were not statistically significant, but the illusion under condition (1) seemed smaller than in the other three conditions. With SOAs for optimal stroboscopic motion, ‘rotation’ paths tended to appear three-dimensional.

Functional and anatomic organization of three-dimensional eye movements in rabbit cerebellar flocculus

1994 ◽  
Vol 72 (1) ◽  
pp. 31-46 ◽  
Author(s):  
J. Van der Steen ◽  
J. I. Simpson ◽  
J. Tan
Keyword(s):  
Eye Movements ◽  
White Matter ◽  
Coordinate System ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Short Latency ◽  
The Other ◽  
Response Component ◽  
Electrical Microstimulation ◽  
Cerebellar Flocculus

1. The three -dimensional, binocular eye movements evoked by electrical microstimulation of the cerebellar flocculus of alert, pigmented rabbits were recorded using the scleral search coil technique. The components of these eye movements were obtained in reference to an orthogonal coordinate system consisting of a vertical axis and two horizontal axes at 45 degrees and 135 degrees azimuth. The azimuth coordinate was taken to increase to both sides from the 0 degrees reference in the direction of the nose. 2. Eye movements were evoked most readily by stimulation (0.2 -ms pulses at 200 Hz for 1 s, intensity < or = 20 microA) at loci in the deep granular layer and the white matter. They consisted of slow (5–20 deg/s) movements. The responses were either binocular, with the eye ipsilateral to the stimulated flocculus usually having the larger amplitude, or were monocular, in which case they were restricted to the ipsilateral eye. 3. The evoked responses were classified according to the combination of the largest measured component of rotation for the two eyes and its sense of rotation (clockwise, CW, or counterclockwise, CCW). Seventy -eight percent of the evoked eye movements could be placed in one of two classes. For one of these classes the largest response component was a short -latency abduction of the ipsilateral eye about its vertical axis (19%), whereas for the other class (59%), the largest response component was a short -latency CCW rotation of the ipsilateral (left) eye about its 135 degrees axis. This response was frequently (50%) accompanied by a smaller short -latency CW rotation of the contralateral (right) eye about its 45 degrees axis. 4. The two main classes of three -dimensional eye movements are associated differentially with anatomically distinguishable compartments that are revealed by acetylcholinesterase histochemistry. Of the five anatomically distinguishable compartments in the floccular white matter, three are predominant. The middle of these three compartments is associated with the vertical axis class of movements, whereas the two adjacent compartments are associated with the 135 degrees class of eye movements. The eye movement relation of the other two, smaller compartments, was not determined. 5. The spatial orientation of the rotation axes of the two main classes of evoked eye movements closely corresponds to that of the preferred axes of the visual climbing fiber input to the flocculus. This suggests that both are organized in a similar coordinate system.(ABSTRACT TRUNCATED AT 400 WORDS)

The Double-Nail Illusion: Experiments on Binocular Vision with Nails, Needles, and Pins

Perception ◽  
1980 ◽  
Vol 9 (6) ◽  
pp. 651-669 ◽  
Author(s):  
Jodi D Krol ◽  
Wim A van de Grind
Keyword(s):  
Quantitative Study ◽  
Neuronal Network ◽  
Binocular Vision ◽  
The Other ◽  
Necessary Condition ◽  
Neuronal Interactions ◽  
Length Width ◽  
Reading Distance ◽  
Straight Ahead ◽  
Network Type

When two nails or similar slender objects are held straight ahead at reading distance, one a few centimetres behind the other and aligned at the same eye level, they are seen side by side rather than one behind the other. A quantitative study of this ‘double-nail’ illusion shows that the objects are judged to be at the positions of the so-called apparent or ghost images known from fusional theories of stereopsis. Most recent fusional theories assume that apparent images are suppressed by neuronal interactions, and the usual absence of percepts corresponding with apparent images is often quoted as an argument against ‘projection’ theories of stereopsis. The double-nail illusion shows, however, that percepts which correspond with apparent images do occur. The results are interpreted in terms of a neuronal-network type of fusional theory, in which the interpretation that corresponds with the minimum overall disparity is assumed to dominate. The following parameters were varied in the experiments: length, width, colour, and contrast for each of the nails; and fixation point position; and the orientation of the nail carrier. The results show that identity of the stimuli is not a necessary condition for the illusion. A stable vergence can be enforced by the double-nail illusion, and with additional nails multistable states of vergence can be obtained.

Symmetry and Uprightness in Visually Perceived Forms

2017 ◽  
Author(s):  
Lydia M. Maniatis
Keyword(s):  
Visual System ◽  
Retinal Image ◽  
Mirror Symmetry ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Two Dimensional ◽  
Retinal Projection ◽  
Retinal Surface ◽  
Axis Of Symmetry

Why do some two-dimensional (2D) drawings look three-dimensional (3D)? The answer is because their projection on our retinas is consistent with a 3D percept that has a “better” shape and orientation than the 2D figure. Whenever a retinal projection is interpreted by the visual system as the projection of a surface that is not frontoparallel (i.e., not parallel to the retinal surface), then the retinal image will differ in shape from the source of the projection in (a) the sizes of its internal angles and/or (b) the relative extents of its surfaces. The latter differences arise because, when an extent is assumed to be receding, then it must also be assumed to have undergone foreshortening in the projection. Using pictures, we can show that the visual system likes more, rather than less, mirror symmetry and a vertical axis of symmetry more than a tilted one.

scholarly journals The Characterization of the Variational Minimizers for Spatial RestrictedN+1-Body Problems

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Fengying Li ◽  
Shiqing Zhang ◽  
Xiaoxiao Zhao
Keyword(s):  
Periodic Solution ◽  
Loop Space ◽  
Vertical Axis ◽  
Small Mass ◽  
The Other ◽  
Necessary Condition ◽  
Zero Mass ◽  
Lagrangian Action ◽  
Variational Minimizers

We use Jacobi's necessary condition for the variational minimizer to study the periodic solution for spatial restrictedN+1-body problems with a zero mass on the vertical axis of the plane forNequal masses. We prove that the minimizer of the Lagrangian action on the anti-T/2 or odd symmetric loop space must be a nonconstant periodic solution for any2≤N≤472; hence the zero mass must oscillate, so that it cannot be always in the same plane with the other bodies. This result contradicts with our intuition that the small mass should always be at the origin.

Three-Dimensional Reconstruction of Two Forms of the Chaperonin GRO EL

1990 ◽  
Vol 48 (1) ◽  
pp. 258-259
Author(s):  
J.L. Carrascosa ◽  
G. Abella ◽  
S. Marco ◽  
M. Muyal ◽  
J.M. Carazo
Keyword(s):  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Series Method ◽  
Three Dimensional Reconstruction ◽  
Structural Components ◽  
E Coli ◽  
Dimensional Reconstruction ◽  
Morphogenetic Factors ◽  
Tilt Series

Chaperonins are a class of proteins characterized by their role as morphogenetic factors. They trantsiently interact with the structural components of certain biological aggregates (viruses, enzymes etc), promoting their correct folding, assembly and, eventually transport. The groEL factor from E. coli is a conspicuous member of the chaperonins, as it promotes the assembly and morphogenesis of bacterial oligomers and/viral structures.We have studied groEL-like factors from two different bacteria:E. coli and B.subtilis. These factors share common morphological features , showing two different views: one is 6-fold, while the other shows 7 morphological units. There is also a correlation between the presence of a dominant 6-fold view and the fact of both bacteria been grown at low temperature (32°C), while the 7-fold is the main view at higher temperatures (42°C). As the two-dimensional projections of groEL were difficult to interprete, we studied their three-dimensional reconstruction by the random conical tilt series method from negatively stained particles.

An Efficient Multiple Description Coding for Multi-View Video Based on the Correlation of Spatial Polyphase Transformed Subsequences

2019 ◽  
Vol 63 (5) ◽  
pp. 50401-1-50401-7 ◽  
Author(s):  
Jing Chen ◽  
Jie Liao ◽  
Huanqiang Zeng ◽  
Canhui Cai ◽  
Kai-Kuang Ma
Keyword(s):  
Video Transmission ◽  
Video Sequence ◽  
Three Dimensional ◽  
The Other ◽  
Multiple Description Coding ◽  
Multiple Description ◽  
Prediction Mode ◽  
Gradient Based ◽  
Directional Interpolation ◽  
Description Coding

Abstract For a robust three-dimensional video transmission through error prone channels, an efficient multiple description coding for multi-view video based on the correlation of spatial polyphase transformed subsequences (CSPT_MDC_MVC) is proposed in this article. The input multi-view video sequence is first separated into four subsequences by spatial polyphase transform and then grouped into two descriptions. With the correlation of macroblocks in corresponding subsequence positions, these subsequences should not be coded in completely the same way. In each description, one subsequence is directly coded by the Joint Multi-view Video Coding (JMVC) encoder and the other subsequence is classified into four sets. According to the classification, the indirectly coding subsequence selectively employed the prediction mode and the prediction vector of the counter directly coding subsequence, which reduces the bitrate consumption and the coding complexity of multiple description coding for multi-view video. On the decoder side, the gradient-based directional interpolation is employed to improve the side reconstructed quality. The effectiveness and robustness of the proposed algorithm is verified by experiments in the JMVC coding platform.

Three-Dimensional Computation during Off-Vertical Axis Rotation (OVAR) in Monkeys

2006 ◽  
Vol 65 (6) ◽  
pp. 429-439 ◽  
Author(s):  
Keisuke Kushiro ◽  
Jun Maruta
Keyword(s):  
Three Dimensional ◽  
Vertical Axis ◽  
Axis Rotation

Performance enhancement of Savonius wind turbine by blade shape and twisted angle modifications

2021 ◽  
pp. 095765092098794
Author(s):  
Ahmed M Nagib Elmekawy ◽  
Hassan A Hassan Saeed ◽  
Sadek Z Kassab
Keyword(s):  
Wind Turbine ◽  
Performance Enhancement ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Cfd Simulations ◽  
Sliding Mesh ◽  
Blade Shape ◽  
Rotor Shape ◽  
Twisting Angle

Three-dimensional CFD simulations are carried out to study the increase of power generated from Savonius vertical axis wind turbines by modifying the blade shape and blade angel of twist. Twisting angle of the classical blade are varied and several proposed novel blade shapes are introduced to enhance the performance of the wind turbine. CFD simulations have been performed using sliding mesh technique of ANSYS software. Four turbulence models; realizable k -[Formula: see text], standard k - [Formula: see text], SST transition and SST k -[Formula: see text] are utilized in the simulations. The blade twisting angle has been modified for the proposed dimensions and wind speed. The introduced novel blade increased the power generated compared to the classical shapes. The two proposed novel blades achieved better power coefficients. One of the proposed models achieved an increase of 31% and the other one achieved 32.2% when compared to the classical rotor shape. The optimum twist angel for the two proposed models achieved 5.66% and 5.69% when compared with zero angle of twist.

scholarly journals On the Kirchhoff-Love Hypothesis (Revised and Vindicated)

2021 ◽  
Author(s):  
Olivier Ozenda ◽  
Epifanio G. Virga
Keyword(s):  
Free Energy ◽  
Dimension Reduction ◽  
Three Dimensional ◽  
Energy Functional ◽  
The Other ◽  
Variational Model ◽  
Two Dimensional ◽  
Elastic Plates ◽  
Kinematic Constraint ◽  
Free Energy Functional

AbstractThe Kirchhoff-Love hypothesis expresses a kinematic constraint that is assumed to be valid for the deformations of a three-dimensional body when one of its dimensions is much smaller than the other two, as is the case for plates. This hypothesis has a long history checkered with the vicissitudes of life: even its paternity has been questioned, and recent rigorous dimension-reduction tools (based on standard $\varGamma $ Γ -convergence) have proven to be incompatible with it. We find that an appropriately revised version of the Kirchhoff-Love hypothesis is a valuable means to derive a two-dimensional variational model for elastic plates from a three-dimensional nonlinear free-energy functional. The bending energies thus obtained for a number of materials also show to contain measures of stretching of the plate’s mid surface (alongside the expected measures of bending). The incompatibility with standard $\varGamma $ Γ -convergence also appears to be removed in the cases where contact with that method and ours can be made.

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