3D Cues Research Articles

Fibrinogen organization at the cell-material interface directs endothelial cell behavior

Fibrinogen (FG) adsorption on surfaces with controlled fraction of —OH groups was investigated with AFM and correlated to the initial interaction of primary endothelial cells (HUVEC). The —OH content was tailored making use of a family of copolymers consisting of ethyl acrylate (EA) and hydroxyl ethyl acrylate (HEA) in different ratios. The supramolecular distribution of FG changed from an organized network-like structure on the most hydrophobic surface (—OH 0) to dispersed molecular aggregate one as the fraction of —OH groups increases, indicating a different conformation by the adsorbed protein. The best cellular interaction was observed on the most hydrophobic (—OH 0) surface where FG assembled in a fibrin-like appearance in the absence of any thrombin. Likewise, focal adhesion formation and actin cytoskeleton development was poorer as the fraction of hydroxy groups on the surface was increased. The biological activity of the surface-induced FG network to provide 3D cues in a potential tissue engineered scaffold, making use of electrospun PEA fibers (—OH0), seeded with human umbilical vein endothelial cells was investigated. The FG assembled on the polymer fibers gave rise to a biologically active network able to direct cell orientation along the fibers (random or aligned), promote cytoskeleton organization and focal adhesion formation.

Aroundplot: Focus+context interface for off-screen objects in 3D environments

In exploring 3D environments from a first-person viewpoint, the narrow field-of-view makes it difficult to search for an off-screen object, a task that becomes even harder if the user is looking through the small screen of a mobile phone. This paper presents Aroundplot, a novel focus+context interface for providing multiple location cues for off-screen objects in an immersive 3D environment. One part of this technique is a mapping method from 3D spherical coordinates to 2D orthogonal fisheye, which tackles the problems of existing 3D location cue displays such as occlusion among the cues and discordance with the human frame of reference. The other part is a dynamic magnification method that magnifies the context in the direction the view is moving to alleviate the distortion of the orthogonal fisheye and thus to support precise movement. In an evaluation, the participants could find the target object for a given location cue faster and more accurately with Aroundplot than with a top-down 2D radar. They were more accurate with Aroundplot than with a 3D arrow cluster when the number of objects was large; however, accuracy with a small number of objects and the search speed with any number of objects were not significantly different.

An Automation System of Rooftop Detection and 3D Building Modeling from Aerial Images

This paper presents a prototype system of rooftop detection and 3D building modeling from aerial images. In this system, without the knowledge of the position and orientation information of the aerial vehicle a priori, the parameters of the camera pose and ground plane are first estimated by simple human---computer interaction. Next, after an over-segmentation of the aerial image by the Mean-Shift algorithm, the rooftop regions are coarsely detected by integrating multi-scale SIFT-like feature vectors with SVM-based visual object recognition. 2D cues alone however might not always be sufficient to separate regions such as parking lots from building roofs. Thus in order to further refine the accuracy of the roof-detection result and remove the misclassified non-rooftop regions such as parking lots, we further resort to 3D depth information estimated based on multi-view geometry. More specifically, we determine whether a candidate region is a rooftop or not according to its height information relative to the ground plane, whereas the candidate region's height information is obtained by a novel, hierarchical, asymmetry correlation-based corner matching scheme. The output of the system will be a water-tight triangle mesh based 3D building model texture mapped with the aerial images. We developed an interactive 3D viewer based on OpenGL and C+?+ to allow the user to virtually navigate the reconstructed 3D scene with mouse and keyboard. Experimental results are shown on real aerial scenes.

Inconsistency of perceived 3D shape

Internal consistency of local depth, slant, and curvature judgments was studied by asking participants to match two 3D surfaces rendered by different mixtures of 3D cues (velocity, texture, and shading). We found that perceptual judgments were not consistent with each other, with cue-specific distortions. Adding multiple cues did not eliminate the inconsistencies of the judgments. These results can be predicted by the Intrinsic Constraint (IC) model according to which the perceptual metric local estimates are a monotonically increasing function of the Signal-to-Noise Ratio of the optimal combination of direct information of 3D shape ( Domini, Caudek, & Tassinari, 2006).

2D images are not sufficient for testing 3D object recognition

Most current models of object recognition assume that initial input is two-dimensional (2D). We tested this assumption by displaying familiar objects in two different conditions; mono, where stimuli were displayed as flat, 2D images, and stereo, where objects were displayed with stereoscopic depth information. In a series of experiments, participants performed a sequential matching task, where an object was rotated up to 180° between presentations. The pattern of viewpoint costs differed markedly between the two conditions. In the mono condition, performance costs due to rotation were highest at rotations of 60° or 120°, a finding attributed to these views having an outline shape that was maximally dissimilar from that at 0°. In the stereo condition, however, performance costs increased monotonically as the rotation size increased, with highest viewpoint costs at 180°. The only exception to this rule came from an experiment in which the initial viewpoint of the object showed it with the axis of elongation running parallel to the viewing plane, that is, a side-on view; here the mono and stereo depictions were very similar (as all components of the object were roughly the same distance from the viewer) and in both conditions recognition performance was better following rotations of 180° than for smaller rotations. These results suggest that 3D objects are encoded with a mixture of 2D and 3D information. As the features of an object have greater variation in 3D space, 3D cues seem to become more salient, and recognition performance may deviate from that predicted by 2D information. As such, these results provide a challenge for experiments that test theoretical models of 3D object recognition by using 2D images; such images may provide an appropriate test of these models under only some viewing conditions.

3D cue combination in spontaneous eye movements

3D cue combination in spontaneous eye movements

Object appearance from integration of 3D and 2D cues in real scenes

Object appearance from integration of 3D and 2D cues in real scenes

2D–3D-based on-board pedestrian detection system

During the next decade, on-board pedestrian detection systems will play a key role in the challenge of increasing traffic safety. The main target of these systems, to detect pedestrians in urban scenarios, implies overcoming difficulties like processing outdoor scenes from a mobile platform and searching for aspect-changing objects in cluttered environments. This makes such systems combine techniques in the state-of-the-art Computer Vision. In this paper we present a three module system based on both 2D and 3D cues. The first module uses 3D information to estimate the road plane parameters and thus select a coherent set of regions of interest (ROIs) to be further analyzed. The second module uses Real AdaBoost and a combined set of Haar wavelets and edge orientation histograms to classify the incoming ROIs as pedestrian or non-pedestrian. The final module loops again with the 3D cue in order to verify the classified ROIs and with the 2D in order to refine the final results. According to the results, the integration of the proposed techniques gives rise to a promising system.

Are discrimination thresholds a valid measure of variance for judgments of slant from texture?

There have been many experiments reported in the literature that have employed discrimination procedures to estimate the variance of observers' slant judgments from texture and binocular disparity, both individually and in combination. The research described in the present article identifies two serious methodological flaws in these studies. Although discrimination thresholds can be influenced by the variance of observers' slant estimates, they can also be affected by systematic biases in observers' judgments, and the presence of 2D cues that are irrelevant to the perception of slant. A series of five experiments is reported to show that: (1) the slants of surfaces specified by texture gradients can be systematically underestimated; (2) surfaces specified by texture gradients appear significantly less slanted than equivalent surfaces specified by binocular disparity; (3) the difference in bias between observers' slant judgments from stereo and texture may be more important than their relative variance in determining how these cues are weighted when presented in combination; (4) observers may be less sensitive to variations in apparent slant from texture than they are to variations in 2D cues that are unrelated to the perception of slant; and (5) these 2D cues may be the primary source of information for discriminating images of textured surfaces. These findings provide strong evidence that the results of prior discrimination studies have been misinterpreted because of the confounding effects of bias and/or 2D cues, and that this has resulted in several questionable conclusions that have been broadly accepted within the field.

Three-dimensional photolithographic patterning of multiple bioactive ligands in poly(ethylene glycol) hydrogels

The biomaterials community is faced with the challenge of imitating a vastly complex, physiological tissue environment. While cellular systems towards this end have been traditionally studied in two dimensions (2D), most cells require three-dimensional (3D) cues to produce a physiologically relevant response. Two-photon absorption laser scanning lithography (TPA-LSL) may be applied to photosensitive hydrogel systems to engineer heterogeneous, 3D microenvironments consisting of precisely patterned bioactive signals. In this work, we have developed new operating parameters and system capabilities for TPA-LSL through the patterning of fluorescently labeled monoacrylate PEG-RGDS within PEG-DA hydrogels. Specifically, we have demonstrated a flexible pattern size range, with features ranging from 1 µm to nearly 1 mm. We have also shown patterns of differing concentrations of the cell adhesive ligand RGDS and correlated observed RGDS fluorescence with laser scan speed and intensity. Finally, we have micropatterned multiple, unique bioactive ligands into distinct, 3D forms within a single hydrogel. The results presented here have significantly developed the capabilities of the TPA-LSL micropatterning technique to allow for the fabrication of heterogeneous, 3D cellular microenvironments, which should prove highly useful for future biomimetic applications.

Bees use three-dimensional information to improve target detection

Bumblebee detection of a flat circular disc (two-dimensional (2D) presentation) and a disc which was presented 10 cm in front of a structured background (and thus provided three-dimensional (3D) cues) was compared. A dual choice test using a Y-maze apparatus was conducted to estimate the minimum visual angle at which the bees were able to detect the disc. At large visual angles of 15, 10 and 5 degrees bees' performance between the 2D and the 3D presentation did not differ. However, when the disc subtended 3 degrees at the bee's eye, the bees performed significantly better when 3D information was available. Overall, bees were able to detect a target subtending a 40% smaller visual angle when it was presented in front of the structured background compared to a 2D presentation. This suggests that previous reports on the limits of target detection in bees using flat stimuli might have underestimated the bees' ability to locate small flowers under natural conditions. Bees use motion parallax, i.e. the apparent relative motion of a stationary object against a background, for perceiving the third dimension. Our data suggest that bumblebees can integrate information from at least two types of feature detectors, motion and area, to improve single target detection.

Comparing 3D Vector Field Visualization Methods: A User Study

In a user study comparing four visualization methods for three-dimensional vector data, participants used visualizations from each method to perform five simple but representative tasks: 1) determining whether a given point was a critical point, 2) determining the type of a critical point, 3) determining whether an integral curve would advect through two points, 4) determining whether swirling movement is present at a point, and 5) determining whether the vector field is moving faster at one point than another. The visualization methods were line and tube representations of integral curves with both monoscopic and stereoscopic viewing. While participants reported a preference for stereo lines, quantitative results showed performance among the tasks varied by method. Users performed all tasks better with methods that: 1) gave a clear representation with no perceived occlusion, 2) clearly visualized curve speed and direction information, and 3) provided fewer rich 3D cues (e.g., shading, polygonal arrows, overlap cues, and surface textures). These results provide quantitative support for anecdotal evidence on visualization methods. The tasks and testing framework also give a basis for comparing other visualization methods, for creating more effective methods, and for defining additional tasks to explore further the tradeoffs among the methods.

Relative contributions of 2D and 3D cues in a texture segmentation task, implications for the roles of striate and extrastriate cortex in attentional selection

Experimental evidence has given strong support to the theory that the primary visual cortex (V1) realizes a bottom-up saliency map (A. R. Koene & L. Zhaoping, 2007; Z. Li, 2002; L. Zhaoping, 2008a; L. Zhaoping & K. A. May, 2007). Unlike the conventional models of texture segmentation, this theory predicted that segmenting two textures in an image I(rel) comprising obliquely oriented bars would become much more difficult when a task-irrelevant texture I(ir) of spatially alternating horizontal and vertical bars is superposed on the original texture I(rel). The irrelevant texture I(ir) interferes with I(rel)'s ability to direct attention. This predicted interference was confirmed (L. Zhaoping & K. A. May, 2007) in the form of a prolonged task reaction time (RT). In this study, we investigate whether and how 3D depth perception, believed to be processed mostly beyond V1 and starting in V2 (J. S. Bakin, K. Nakayama, & C. D. Gilbert, 2000; B. G. Cumming & A. J. Parker, 2000; F. T. Qiu & R. von der Heydt, 2005; R. von der Heydt, H. Zhou, & H. S. Friedman, 2000), contribute additionally to direct attention. We measured the reduction of the interference or the RT when the position of the texture grid for I(ir) was offset horizontally from that for I(rel), forming an offset, 2D, stimulus. This reduction was compared with that when this positional offset was only present in the input image to one eye, or when it was in the opposite directions in the images for the two eyes, creating a 3D stimulus with a depth separation between I(ir) and I(rel). The contribution by 3D processes to attentional guidance would be manifested by any extra RT reduction associated with the 3D stimulus over the offset 2D stimulus. This 3D contribution was not present unless the task was so difficult that RT (by button press) based on 2D cues alone was longer than about 1 second. Our findings suggest that, without other top-down factors, V1 plays a dominant role in attentional guidance during an initial window of processing, while cortical areas beyond V1 play an increasing role in later processing. Subject-dependent variations in the manifestations of the 3D effects also suggest that this later, 3D, contribution to attentional guidance can be easily influenced by top-down control.

Area MT pattern motion selectivity by integrating 1D and 2D motion features from V1 - a neural model

Event Abstract Back to Event Area MT pattern motion selectivity by integrating 1D and 2D motion features from V1 - a neural model Problem The neural mechanisms of detecting, integrating, and disambiguating visual motion still remain largely a puzzle. While many neurons in area V1 show coarse direction and speed selectivity signaling component motion direction, evidence suggests that end-stop cells in V1 compute the true motion direction for 2D image features (Pack et al., Neuron 39, 2003). In area MT, neurons have been found that are selective to speed and respond to pattern motion direction in the case of plaids from combined differently oriented gratings (Movshon et al., Pattern Recognition Mechanisms, 1985). For elongated bars, MT neurons resolve the so-called aperture problem to signal the correct object motion after a temporal course of disambiguation (Pack&Born, Nature 409, 2001). The construction of selectivity to pattern motion from component selective input is a topic of ongoing research. Different experiments suggest that the visual system might use computational strategies of integrating different motion directions or selecting localized features (Pack&Born, The Senses: A Comprehensive Reference, 2008). Methods We propose a neurodynamical model of motion integration in areas V1, MT, and MSTv which unifies the integrationist and selectionist concepts. Normal flow responses are initially detected by model V1 simple/complex cells while inhibitory interactions between cells at different V1 laminae generate local end-stop responses after a temporal delay. These responses are integrated for a short temporal episode and enhanced to generate strong direction signals. MT neurons then receive input from V1 complex and end-stop neurons (size ratio 1:5, direction tuning +/-40°). The integration of component selective responses leads to weak pattern direction selectivity in MT, further sharpened by the input from localized end-stop neurons. Feedback from MT to V1 enhances neurons with feature selectivity and slightly reduces normal flow responses near localized features. Feedforward and feedback connections between MT and MSTv (size ratio 1:1.25) disambiguate MT responses along extended outline boundaries. Results and Conclusion To investigate the aperture problem, we tested the model with a vertically aligned bar moving in diagonal direction. Consistent with neurophysiological findings (Pack&Born, Nature 409, 2001), after few iterations MT neurons showed sharp speed and direction tuning for the correct velocity, while the tuning of V1 neurons only slightly changed. Originating from 2D signals at corners, the correct flow was further propagated in MT along the stimulus by each iteration while propagation time increased with bar length (Born et al., Prog. Brain Res. 140, 2002). For a plaid stimulus, model MT neurons were tuned to pattern motion after some iterations, while V1 neurons indicated normal flow responses along the plaid components, except for end-stop neurons located at crossings. Hence, V1 neurons already provided some of the correct 2D cues, their overall tuning nevertheless remained coarse in speed and direction. To conclude, the integration of 1D and 2D V1 motion features in MT as proposed by our model suggests the generation of MT cell pattern selectivity based on component integration and feature selection. The model explains findings of various neurophysiological experiments and unifies different modeling approaches into one framework. Supported by EU-project 027198 (Decisions-in-Motion) Conference: Computational and systems neuroscience 2009, Salt Lake City, UT, United States, 26 Feb - 3 Mar, 2009. Presentation Type: Poster Presentation Topic: Poster Presentations Citation: (2009). Area MT pattern motion selectivity by integrating 1D and 2D motion features from V1 - a neural model. Front. Syst. Neurosci. Conference Abstract: Computational and systems neuroscience 2009. doi: 10.3389/conf.neuro.06.2009.03.163 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Feb 2009; Published Online: 04 Feb 2009. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Google Google Scholar PubMed Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Attention-Dependent Representation of a Size Illusion in Human V1

One of the most fundamental properties of human primary visual cortex (V1) is its retinotopic organization, which makes it an ideal candidate for encoding spatial properties, such as size, of objects. However, three-dimensional (3D) contextual information can lead to size illusions that are reflected in the spatial pattern of activity in V1 [1]. A critical question is how complex 3D contextual information can influence spatial activity patterns in V1. Here, we assessed whether changes in the spatial distribution of activity in V1 depend on the focus of attention, which would be suggestive of feedback of 3D contextual information from higher visual areas. We presented two 3D rings at close and far apparent depths in a 3D scene. When subjects fixated its center, the far ring appeared to be larger and occupy a more eccentric portion of the visual field, relative to the close ring. Using functional magnetic resonance imaging, we found that the spatial distribution of V1 activity induced by the far ring was also shifted toward a more eccentric representation of the visual field, whereas that induced by the close ring was shifted toward the foveal representation, consistent with their perceptual appearances. This effect was significantly reduced when the focus of spatial attention was narrowed with a demanding central fixation task. We reason that focusing attention on the fixation task resulted in reduced activity in--and therefore reduced feedback from--higher visual areas that process the 3D depth cues.

On Visual, Vibrotactile, and 3D Audio Directional Cues for Dismounted Soldier Waypoint Navigation

We compared a visual GPS, a tactile torso belt, and a 3D audio display in a waypoint navigation task for dismounted soldiers. Using these displays one at a time, the soldier's main tasks were to walk as fast and straight as possible towards the waypoints while visually scanning the terrain for detection of target flags. The results showed that all three types of displays gave similar navigation precision and target detection performance. The visual display entailed a somewhat higher navigation speed than the tactile and 3D audio displays. Both the visual and 3D audio displays, however, were rated as directing attention away from the terrain more than the tactile display. Compared to the tactile display, a higher mental workload was reported for the 3D audio, which was also rated least suitable for operational use in navigation tasks. Yet, the soldiers' ability to localize directions to waypoints with the 3D audio display may point to its potential use for radio communication and cueing of directions to threats. In an overall evaluation, eight soldiers preferred the tactile display and four the visual, while none preferred the 3D audio. We discuss the results mainly regarding shortcomings of the study and the possibility of developing and combining the three display types for the dismounted soldier.

NEUROSENSORY ECOLOGY IN THE JEB

It is often difficult to imagine how other people perceive the world, let alone other species, so when Ken Lukowiak was approached by The JEB's Editor in Chief, Hans Hoppeler, to draw together reviews discussing Neurosensory Ecology, he decided to steer clear of the usual sensory topics. Taking an

Endoscopic navigation for minimally invasive suturing

Manipulating small objects such as needles, screws or plates inside the human body during minimally invasive surgery can be very difficult for less experienced surgeons due to the loss of 3D depth perception. Classical navigation techniques are often incapable of providing support in such situations, as the augmentation of the scene with the necessary artificial markers - if possible at all - is usually cumbersome and leads to increased invasiveness. We present an approach relying solely on a standard endoscope as a tracking device for determining the pose of such objects, using the example of a suturing needle. The resulting pose information is then used to generate artificial 3D cues on the 2D screen to provide optimal support for surgeons during tissue suturing. In addition, if an external tracking device is provided to report the endoscope's position, the suturing needle can be directly tracked in the world coordinate system. Furthermore, a visual navigation aid can be incorporated if a 3D surface is intraoperatively reconstructed from the endoscopic video stream or registered from preoperative imaging.

2D vs. 3D Visual Cues for Altitude Maintenance in Low-Altitude Flight

Previous research on altitude maintenance in low-altitude flight has focused either on cues provided by 2D features in the visual scene (e.g., splay angle) or on visual cues provided by the presence of 3D objects in the scene (e.g., occlusion). Therefore, little is known about the relative importance of 2D and 3D cues in altitude maintenance. We systematically varied the position variability, height, and pattern of surface elements in a simulated low-level flight environment to vary the salience of 2D and 3D visual cues. For 2D objects, altitude variability increased as a function of object position variability indicating that splay and depression angles are not reliable cues for terrains with irregularly spaced objects. For 3D objects, altitude variability increased less (or not at all) as a function of position variability indicating that the cues provided by 3D objects such as occlusion and motion parallax are the dominant visual cues for altitude maintenance for natural terrains with irregularly spaced objects.

Spatial term apprehension with a reference object’s rotation in three-dimensional space

It has been reported that the overall shapes of spatial categorical patterns of projective spatial terms such as above and below are not influenced by the rotation of a reference object on a two-dimensional (2D) upright plane. However, is this also true in three-dimensional (3D) space? This study shows the dynamic aspects of the apprehension of projective spatial terms in 3D space by detailing how the rotation of a reference object with an inherent front influences the apprehension of projective spatial terms on a level plane by mapping their spatial categorical patterns. The experiment was designed to examine how spatial categorical patterns on a level plane changed with the rotation of a reference object with an inherent front in 3D computer graphics space. We manipulated the rotation of a reference object with an inherent front at three levels (0 degrees , 90 degrees , and 180 degrees rotations) and examined how such manipulation changed the overall spatial categorical patterns of four basic Japanese projective spatial terms: mae, ushiro, hidari, and migi (similar to in front of, behind, to the left of, and to the right of in English, respectively). The results show that spatial term apprehension was affected by the rotation of the reference object in 3D space. In particular, rotation influenced the mae-ushiro and hidari-migi systems differently. The results also imply that our understanding of projective spatial terms on a level plane in 3D space is affected dynamically by visual information from 3D cues.