scholarly journals No single, stable 3D representation can explain pointing biases in a spatial updating task

2018 ◽  
Author(s):  
Jenny Vuong ◽  
Andrew W. Fitzgibbon ◽  
Andrew Glennerster
Keyword(s):  
3D Model ◽  
Head Movements ◽  
Visual Direction ◽  
Spatial Updating ◽  
Pointing Errors ◽  
Immersive Virtual Environment ◽  
Real Scene ◽  
True Location ◽  
3D Representation ◽  
The Moment

AbstractPeople are able to keep track of objects as they navigate through space, even when objects are out of sight. This requires some kind of representation of the scene and of the observer’s location but the form this representation might take is debated. We tested the accuracy and reliability of observers’ estimates of the visual direction of previously-viewed targets. Participants viewed 4 objects from one location, with binocular vision and small head movements giving information about the 3D locations of the objects. Without any further sight of the targets, participants walked to another location and pointed towards them. All the conditions were tested in an immersive virtual environment and some were also carried out in a real scene. Participants made large, consistent pointing errors that are poorly explained by any consistent 3D representation. Instead, if a 3D representation is to account for the data it would need to be one where the target boxes were squashed, almost into a plane, quite far away from the true location of the boxes and in different places depending on the orientation of the obscuring wall at the moment the participant points. In short, our data show that the mechanisms for updating visual direction of unseen targets are not based on a stable 3D model of the scene, even a distorted one.

scholarly journals Blind footballers direct their head towards an approaching ball during ball trapping

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Takumi Mieda ◽  
Masahiro Kokubu
Keyword(s):  
Rotation Angle ◽  
Sagittal Plane ◽  
Early Time ◽  
Head Rotation ◽  
Head Movements ◽  
Football Players ◽  
Trunk Rotation ◽  
The Moment ◽  
Head Rotations ◽  
Egocentric Direction

AbstractIn blind football, players predict the sound location of a ball to underpin the success of ball trapping. It is currently unknown whether blind footballers use head movements as a strategy for trapping a moving ball. This study investigated characteristics of head rotations in blind footballers during ball trapping compared to sighted nonathletes. Participants performed trapping an approaching ball using their right foot. Head and trunk rotation angles in the sagittal plane, and head rotation angles in the horizontal plane were measured during ball trapping. The blind footballers showed a larger downward head rotation angle, as well as higher performance at the time of ball trapping than did the sighted nonathletes. However, no significant differences between the groups were found with regards to the horizontal head rotation angle and the downward trunk rotation angle. The blind footballers consistently showed a larger relative angle of downward head rotation from an early time point after ball launching to the moment of ball trapping. These results suggest that blind footballers couple downward head rotation with the movement of an approaching ball, to ensure that the ball is kept in a consistent egocentric direction relative to the head throughout ball trapping.

scholarly journals GUIDELINES FOR AUTHORS PREPARING A FULL PAPER TO BE SUBMITTED TO ISPRS EVENTS

2021 ◽  
Vol XLIII-B2-2021 ◽  
pp. 613-618
Author(s):  
P. Ortiz-Coder ◽  
R. Cabecera
Keyword(s):  
Case Studies ◽  
3D Model ◽  
Laser Scanner ◽  
Point Clouds ◽  
Model Generation ◽  
Selection Algorithm ◽  
Full Paper ◽  
Historical Heritage ◽  
The Moment ◽  
New Generation

Abstract. In recent years, a new generation of instruments has appeared that are motion-based capture. These systems are based on a combination of techniques, among which LIDAR stands out. In this article we present a new proposal for a 3D model generation instrument based on videogrammetry. The prototype designed consists of two cameras connected to a computer system. One of the cameras is in charge of running VisualSLAM and guiding the user in real time at the moment of data acquisition; the other camera, with a higher resolution, saves the images and, thanks to a refined 3D-Based frame selection algorithm, processes them using automatic photogrammetric procedures, generating one or more point-clouds that are integrated to give way to a high-density and high-precision 3D colour point-cloud.The paper evaluates the proposal with four case studies: two of an urban nature and two related to historical heritage. The resulting models are confronted with the Faro Focus3D X330 laser scanner, classic photogrammetric procedures with reflex camera and Agisoft metashape software and are also confronted with precision points measured with a total station. The case studies show that the proposed system has a high capture speed, and that the accuracy of the models can be competitive in many areas of professional surveying and can be a viable alternative for the creation of instruments based on videogrammetry.

Scalable 3D Representation for 3D Video in a Large-Scale Space

2004 ◽  
Vol 13 (2) ◽  
pp. 164-177 ◽  
Author(s):  
Itaru Kitahara ◽  
Yuichi Ohta
Keyword(s):  
Large Scale ◽  
Processing Time ◽  
3D Model ◽  
Scale Space ◽  
3D Video ◽  
Experimental Results ◽  
Multiple Cameras ◽  
3D Objects ◽  
3D Representation ◽  
Viewing Position

In this paper, we introduce our research aimed at realizing a 3D video system in a very large-scale space such as a soccer stadium or concert hall. We propose a method for describing the shape of a 3D object with a set of planes in order to effectively synthesize a novel view of the object. The most effective layout of the planes can be determined based on the relative locations of the observer's viewing position, multiple cameras, and 3D objects. We describe a method for controlling the LOD of the 3D representation by adjusting the planes' orientation, interval, and resolution. The data size of the 3D model and the processing time can be reduced drastically. The effectiveness of the proposed method is demonstrated by our experimental results.

FACE AND FACIAL FEATURE TRACKING USING DEFORMABLE MODELS

2004 ◽  
Vol 04 (03) ◽  
pp. 499-532 ◽  
Author(s):  
F. DORNAIKA ◽  
J. AHLBERG
Keyword(s):  
3D Model ◽  
Robust Statistics ◽  
Rigid Motion ◽  
Facial Feature ◽  
3D Models ◽  
Input Image ◽  
Head Movements ◽  
3D Tracking ◽  
Feature Correspondence ◽  
Active Appearance

In this paper, we address the 3D tracking of pose and animation of the human face in monocular image sequences using deformable 3D models. The main contributions of this paper are as follows. First, we show how the robustness and stability of the Active Appearance Algorithm can be improved through the inclusion of a simple motion compensation based on feature correspondence. Second, we develop a new method able to adapt a deformable 3D model to a face in the input image. Central to this method is the decoupling of global head movements and local non-rigid deformations/animations. This decoupling is achieved by, first, estimating the global (rigid) motion using robust statistics and a statistical model for face texture, and then, adapting the 3D model to possible local animations using the concept of the Active Appearance Algorithm. This proposed method constitutes a significant step towards reliable model-based face trackers since the strengths of complementary tracking methodologies are combined. Experiments evaluating the effectiveness of the methods are reported. Adaptation and tracking examples demonstrate the feasibility and robustness of the developed methods.

An Efficient Method for Creating Virtual Spaces for Virtual Reality

2014 ◽  
Author(s):  
Zhou Zhang ◽  
Mingshao Zhang ◽  
Yizhe Chang ◽  
Sven K. Esche ◽  
Constantin Chassapis
Keyword(s):  
Virtual Reality ◽  
Efficient Method ◽  
Point Cloud ◽  
3D Model ◽  
Virtual Space ◽  
Virtual Laboratory ◽  
The Real ◽  
Virtual Spaces ◽  
Real Scene ◽  
Measuring Tool

A virtual space (VS) is an indispensable component of a virtual environment (VE) in virtual reality (VR). Usually, it is created using general tools and skills that are independent of the users’ specific applications and intents. Creating a VS by surveying the real world with traditional measuring tools or creating virtual features with CAD software involves many steps and thus is time consuming and complicated. This renders the construction of VEs difficult, impairs their flexibility and hampers their widespread usage. In this paper, an efficient method for creating VSs with a handheld camera is introduced. In this approach, the camera is used as a measuring tool that scans the real scene and obtains the corresponding surface information. This information is then used to generate a virtual 3D model through a series of data processing procedures. Firstly, the camera’s pose is traced in order to locate the points of the scene’s surface, whereby these surface points form a point cloud. Then, this point cloud is meshed and the mesh elements are textured automatically one by one. Unfortunately, the virtual 3D model resulting from this procedure represents an impenetrable solid and thus collision detection would prevent the avatars from entering into this VS. Therefore, an approach for eliminating this restriction is proposed here. Finally, a game-based virtual laboratory (GBVL) for an undergraduate mechanical engineering class was developed to demonstrate the feasibility of the proposed methodology. The model format used in Garry’s Mod (GMod) is also found in other VEs, and therefore the method proposed here can be straightforwardly generalized to other VE implementations.

Saccadic Compensation for Smooth Eye and Head Movements During Head-Unrestrained Two-Dimensional Tracking

2010 ◽  
Vol 103 (1) ◽  
pp. 543-556 ◽  
Author(s):  
P. M. Daye ◽  
G. Blohm ◽  
P. Lefèvre
Keyword(s):  
Smooth Pursuit ◽  
Latency Period ◽  
Saccade Latency ◽  
Head Movements ◽  
Spatial Updating ◽  
Head Restraint ◽  
The Gaze ◽  
Saccadic System ◽  
Restrained Condition ◽  
Independent Parameters

Spatial updating is the ability to keep track of the position of world-fixed objects while we move. In the case of vision, this phenomenon is called spatial constancy and has been studied in head-restraint conditions. During head-restrained smooth pursuit, it has been shown that the saccadic system has access to extraretinal information from the pursuit system to update the objects' position in the surrounding environment. However, during head-unrestrained smooth pursuit, the saccadic system needs to keep track of three different motor commands: the ocular smooth pursuit command, the vestibuloocular reflex (VOR), and the head movement command. The question then arises whether saccades compensate for these movements. To address this question, we briefly presented a target during sinusoidal head-unrestrained smooth pursuit in darkness. Subjects were instructed to look at the flash as soon as they saw it. We observed that subjects were able to orient their gaze to the memorized (and spatially updated) position of the flashed target generally using one to three successive saccades. Similar to the behavior in the head-restrained condition, we found that the longer the gaze saccade latency, the better the compensation for intervening smooth gaze displacements; after about 400 ms, 62% of the smooth gaze displacement had been compensated for. This compensation depended on two independent parameters: the latency of the saccade and the eye contribution to the gaze displacement during this latency period. Separating gaze into eye and head contributions, we show that the larger the eye contribution to the gaze displacement, the better the overall compensation. Finally, we found that the compensation was a function of the head oscillation frequency and we suggest that this relationship is linked to the modulation of VOR gain. We conclude that the general mechanisms of compensation for smooth gaze displacements are similar to those observed in the head-restrained condition.

scholarly journals The first observed stellar occultations by the irregular satellite Phoebe (Saturn IX) and improved rotational period

2019 ◽  
Vol 492 (1) ◽  
pp. 770-781
Author(s):  
A R Gomes-Júnior ◽  
M Assafin ◽  
F Braga-Ribas ◽  
G Benedetti-Rossi ◽  
B E Morgado ◽  
...  
Keyword(s):  
3D Model ◽  
Rotation Period ◽  
Light Curves ◽  
Rotational Period ◽  
Shape Model ◽  
Stellar Occultation ◽  
Stellar Occultations ◽  
The Difference ◽  
The Moment ◽  
Gaia Dr2

ABSTRACT We report six stellar occultations by Phoebe (Saturn IX), an irregular satellite of Saturn, obtained between mid-2017 and mid-2019. The 2017 July 6 event was the first stellar occultation by an irregular satellite ever observed. The occultation chords were compared to a 3D shape model of the satellite obtained from Cassini observations. The rotation period available in the literature led to a sub-observer point at the moment of the observed occultations where the chords could not fit the 3D model. A procedure was developed to identify the correct sub-observer longitude. It allowed us to obtain the rotation period with improved precision compared to the currently known value from literature. We show that the difference between the observed and the predicted sub-observer longitude suggests two possible solutions for the rotation period. By comparing these values with recently observed rotational light curves and single-chord stellar occultations, we can identify the best solution for Phoebe’s rotational period as 9.27365 ± 0.00002 h. From the stellar occultations, we also obtained six geocentric astrometric positions in the ICRS as realized by the Gaia DR2 with uncertainties at the 1-mas level.

scholarly journals No single, stable 3D representation can explain pointing biases in a spatial updating task

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jenny Vuong ◽  
Andrew W. Fitzgibbon ◽  
Andrew Glennerster
Keyword(s):  
Spatial Updating ◽  
3D Representation

scholarly journals STUDY OF THE DYNAMICS OF THE EXOSKELETON ACTUATING UNIT

2021 ◽  
Vol 6 (11) ◽  
pp. 114-121
Author(s):  
Z. Isabekov ◽  
K. Moroz ◽  
M. Kerimzhanova
Keyword(s):  
Power Plants ◽  
3D Model ◽  
Theoretical Study ◽  
Human Movement ◽  
Kinematic Scheme ◽  
Control Laws ◽  
Generalized Coordinates ◽  
Cad System ◽  
Electrohydraulic Drive ◽  
The Moment

A person has more than 300 degrees of mobility, but it is practically impossible to recreate such a kinematic scheme. In this article, a kinematic scheme of the exoskeleton is proposed that is most necessary for human movement. A 3D model of the exoskeleton actuating unit with an electrohydraulic drive has been developed in the CAD system and the values of masses, coordinates of mass centers, inertia tensors of the links of the exoskeleton actuating unit have been calculated. A launch file has been developed in the MATLAB environment for modeling the dynamics of the exoskeleton actuating unit. The control laws in the degrees of mobility of the actuating unit of the exoskeleton are selected. As a result of the theoretical study, the ranges of changes in the generalized coordinates for the joints under study are determined. The dependences of the power and the moment in the joints 9, 10 on time are obtained. The conducted studies have shown that lifting the leg will require more energy and this makes it necessary to develop power plants, explore various types of drives and ways to control them energy-efficiently. The obtained data can serve in the development of a medical exoskeleton.

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