Stereoscopic Technique Research Articles

Projection of realistic three-dimensional photogrammetry models using stereoscopic display: A technical note.

The 3D stereoscopic technique consists in providing the illusional perception of depth of a given object using two different images mimicking how the right and left eyes capture the object. Both images are slightly different and when overlapped gives a three-dimensional (3D) experience. Considering the limitations for establishing surgical laboratories and dissections courses in some educational institutions, techniques such as stereoscopy and photogrammetry seem to play an important role in neuroanatomy and neurosurgical education. The aim of this study was to describe how to combine and set up realistic models acquired with photogrammetry scans in 3D stereoscopic projections. Three donors, one dry skull, embalmed brain and head, were scanned using photogrammetry. The software used for displaying the final realistic 3D models (Blender, Amsterdam, the Netherlands) is a free software and allows stereoscopic projection without compromising the interactivity of each model. By default, the model was exported and immediately displayed as a red cyan 3D mode. The 3D projector used in the manuscript required a side-by-side 3D mode which was set up with simple commands on the software. The final stereoscopy projection offered depth perception and a visualization in 360° of each donor; this perception was noted especially when visualizing donors with different cavities and fossae. The combination of 3D techniques is of paramount importance for neuroanatomy education. Stereoscopic projections could provide a valuable tool for neuroanatomy instruction directed at clinical trainees and could be especially useful when access to laboratory-based learning is limited.

Straightforward Stereoscopic Techniques for Archaeometric Interpretation of Archeological Artifacts

Stereoscopic visualization plays a significant role in the detailed and accurate interpretation of various geometric features on the surface of archaeological artifacts, which can be challenging to perceive using conventional two-dimensional visualizations. Moreover, virtual 3D models can be shared with other archaeologists for interpretation and the exchange of opinions. The hardware requirements for rendering stereoscopic 3D models are often readily available on desktop computers, or require only a minimal investment for implementation. This article focuses on creating stereoscopic visualizations of a stylized dove-shaped cult vessel for a virtual museum project. The term “visualization” is defined, emphasizing its significance and everyday applications. The camerawork techniques and processes involved in stereoscopic image production, including anaglyph imaging and polarization, are described. Blender (community-driven project under the GNU General Public License (GPL), Blender Foundation is a member of Open Invention Network, Khronos, Linux Foundation and the Academy Software Foundation) and StereoPhoto Maker (Muttyan, Japan) are reviewed as they relate to the production process of stereoscopic visualizations using open-source software. A series of static stereoscopic visualizations, along with two dynamic stereoscopic examples, are created, one using the anaglyph process, and the other using polarization. Lastly, the article discusses the contribution of stereoscopic visualizations to the interpretation of archaeological artifacts and suggests the optimal parameters for creating stereoscopic visualizations.

Synthesis and Characterization of Highly Deformable Multilayer Magnetoactive Elastomers with Magnetically Soft Particles

Herein, a new highly deformable magnetoactive elastomeric material is developed. The elastomer is composed of a silicon‐based matrix and soft‐magnetic Fe microparticles. It presents a nonuniform multilayer internal structure, with highest particle concentration in one‐half of the thickness. These elastomers are produced in sheet and tubular formats, wherein multilayer distribution of the components is achieved by the gravitational and centrifugal force respectively. The study of the rheological properties shows a high change in the dynamic modulus of the elastomer in the presence of magnetic field, which is representative of a high magnetorheological effect. Regarding the deformability of the elastomer, to monitor the displacements and curvatures generated under the action of a magnetic field, an optical, noninvasive, and magnetic field‐insensitive system based on 3D stereoscopic technique is employed. Using this method, the digitization of the upper curved surface of the elastomer as a function of the applied magnetic field is obtained. From the digitized surfaces, the deformation of the material in response to a magnetic field is calculated, reaching deformations up to 23.7% at 207 kA m−1. Moreover, the deformation level is linearly variable and controllable by the strength of the applied magnetic field, allowing dynamic deformation of the material.

Embryonic and aglomerular kidney development in the bay pipefish, Syngnathus leptorhynchus

In this report we describe the embryogenesis of the bay pipefish, Syngnathus leptorhynchus, and the organogenesis of its aglomerular kidney. Early development was analyzed via a series of montages and images documenting embryos collected from the brood pouches of pregnant males. Despite differences in terminal morphology between pipefish and common teleost models such as medaka and zebrafish, the embryogenesis of these highly advanced fishes is generally similar to that of other fishes. One of the unique features of these fishes is their utilization of an aglomerular kidney. Histological analysis revealed a single long, unbranched kidney tubule in late embryos. The development and structure of this organ was further investigated by cloning the sodium potassium ATPase alpha subunit, atp1a, from S. leptorhynchus and developing whole mount fluorescent in situ hybridization protocols for embryos of this species. Fluorescent stereoscopic and confocal visualization techniques were then used to characterize the 3D morphology of aglomerular kidneys in intact embryos. In all embryonic stages characterized, the aglomerular kidney is a single unbranched tube extending from just behind the head to the cloaca.

Compact Midwave Imaging System: Results from an Airborne Demonstration

The Compact Midwave Imaging System (CMIS) is a wide field of view, multi-angle, multi-spectral pushframe imager that relies on the forward motion of the satellite to create a two-dimensional (2D) image swath. An airborne demonstration of CMIS was successfully completed in January–February 2021 on the NASA Langley Research Center Gulfstream III. The primary objective of the four-flight campaign was to demonstrate the capability of this unique instrument to perform stereo observations of clouds and other particulates (e.g., smoke) in the atmosphere. It is shown that the midwave infrared (MWIR) spectral bands of CMIS provide a unique 24/7 capability with high resolution for accurate stereo sensing. The instrument relies on new focal plane array (FPA) technology, which provides excellent sensitivity at much warmer detector temperatures than traditional technologies. This capability enabled a compact, low-cost design that can provide atmospheric motion vectors and cloud heights to support requirements for atmospheric winds in the 2017–2027 Earth Science Decadal Survey. Applications include day/night observations of the planetary boundary layer, severe weather, and wildfires. A comparison with current space-based earth science instruments demonstrates that the SWIR/MWIR multi-spectral capability of CMIS is competitive with larger, more expensive instrumentation. Imagery obtained over a controlled burn and operating nuclear power plant demonstrated the sensitivity of the instrument to temperature variations. The system relies on a mature stereoscopic imaging technique applied to the same scene from two independent platforms to unambiguously retrieve atmospheric motion vectors (AMVs) with accurate height assignment. This capability has been successfully applied to geostationary and low-earth orbit satellites to achieve excellent accuracy. When applied to a ground-point validation case, the accuracy for the CMIS aircraft observations was 20 m and 0.3 m/s for cloud heights and motion vectors, respectively. This result was confirmed by a detailed error analysis with analytical and covariance models. The results for CMIS cases with underflights of Aeolus, CALIPSO, and Aqua provided a good validation of expected accuracies. The paper also showed the feasibility of accommodating CMIS on CubeSats to enable multiple instruments to be flown in a leader–follower mode.

Comparison between 3D-reconstruction optical methods applied to bulge-tests through a feed-forward neural network

The mechanical behaviour of rubber-like materials can be investigated through numerous techniques that differ from each other in costs, execution times and parameters described. Bulge test method proved helpful for hyperelastic membranes under plane and equibiaxial stress state. In the present study, bulge tests in force control were carried out on SBR 20% CB-filled specimens. 3D reconstructions of the dome were achieved through two different stereoscopic techniques, the epipolar geometry and the Digital Image Correlation. Through a Feed-Forward Neural Network (FFNN), these reconstructions were compared with the measurements by a laser triangulation sensor taken as reference. 3D-DIC reconstruction was found to be more accurate. Indeed, bias errors of the 3D-DIC and epipolar techniques with respect to the relative reference values, under creep condition, were 0.53 mm and 0.87 mm, respectively.<br /><br />

The spermatophore of the black field cricket, Teleogryllus commodus (Walker, 1869) (Orthoptera: Gryllidae) – a stereoscopic investigation

The contribution includes the detailed investigation of the spermatophore produced by the male black field cricket with the help of stereoscopic visualization techniques. For this purpose, sperm capsules of selected crickets were isolated and prepared for light- and electronmicroscopic analysis. Production of stereoscopic semi-images and red-cyan anaglyphs was carried out by application of the formerly introduced object rotation method and, alternatively, by use of computer-aided object depth mapping (ODM), where three-dimensional information is obtained from a single photograph. As found by stereoscopic imaging, the spermatophore of the black field cricket consists of a spherical ampulla with a diameter of 0.5 mm, a tube measuring up to 3.5 mm in length, and an anchor plate serving for the fixation of the capsule at the aperture of the female genital chamber during copulation. Single spermatozoa are characterized by an organized arrangement within the ampulla, so that their release from the sperm vessel is significantly facilitated. The study clearly demonstrates that spatial imaging is not only useful for the purpose of presentation, but also for a more detailed analysis of diverse insect structures.

Into the Vœrtex: Case study of a stereoscopic abstract animation installation

In Max Hattler’s stereoscopic installation Vœrtex two-dimensional abstract animation is turned into immersive images with strong three-dimensional depth. Utilizing a two-screen, semi-Cave Automatic Virtual Environment, Vœrtex creates a unique viewing experience for the viewer, a hybrid space situated halfway between immersion-in-abstraction and the real world of the gallery space, allowing the viewer to be in two spaces simultaneously. This article discusses the technical set-up, production processes and stereoscopic techniques, including binocular colour rivalry and depth displacements employed in Vœrtex. This is followed by a discussion of Vœrtex in relation to the concept of lucidity and an audience study into viewers’ perception of the work. The hybrid set-up of Vœrtex, combining both stereoscopic and interactive visual texts, allows for a sense of creative inspiration and inquiry into the dreaming mind, and participants can actively choose to explore different aspects of their perception by oscillating between two divergent states: an immersive dream sensation and a sense of being anchored in the real world.

Volumetric PIV measurement for capturing the port flow characteristics within annular gas turbine combustors

The three-dimensional flows within a full featured, unmodified annular gas turbine combustor have been investigated using a scanned stereoscopic PIV measurement technique. Volumetric measurements have been achieved by rigidly translating a stereoscopic PIV system to scan measurements around the combustor, permitting reconstruction of volumetric single-point statistics. Delivering the measurements in this way allows the measurement of larger volumes than are accessible using techniques relying upon high depth of field imaging. The shallow depth of field achieved in the stereoscopic configuration furthermore permits measurements in close proximity to highly detailed geometry. The measurements performed have then been used to assess the performance of the combustor port flows, which are central to the emissions performance and temperature/velocity profile at turbine inlet. Substantially differing performance was observed in the primary ports with circumferential position, which was found to influence the behaviour of the second secondary port jets. The measurements indicated that the interaction between the primary and secondary jets occurred due to variations in the external boundary conditions imposed by the annular passages in which the combustor is located.Graphic abstract

Cine 3D español: experiencias del cine estereoscópico 3D durante los años del franquismo

Este artículo investiga los orígenes de la producción española en cine estereoscópico 3D en la década de los cincuenta y sesenta, en pleno franquismo. La rapidez en la producción de cortometrajes tridimensionales muestra un conocimiento de la tecnología de producción foránea y una enorme flexibilidad y agilidad a la hora de crear contenidos 3D en España. El objetivo principal de esta investigación es identificar aquellas producciones cinematográficas españolas realizadas con técnicas estereoscópicas desde la propia filmación o tras su adecuación con técnicas de posproducción para la proyección. La hipótesis es que las muestras puntuales que ha dado la cinematografía española de cintas tridimensionales han respondido a fenómenos de moda pasajeros y no han supuesto hitos de importancia comercial o artística, más allá de la experimentación con las posibilidades del formato. Con todo, recogen una voluntad de aperturismo del cine español hacia las nuevas tecnologías y hacia la búsqueda del público. Aplicaremos una metodología basada en el estudio de caso, a partir de la revisión bibliográfica de fuentes primarias y secundarias dedicadas a la producción y la exhibición cinematográfica en España. Los resultados muestran que la influencia de la cinematografía estadounidense en su vertiente más tecnológica y comercial es evidente, incluso si los organismos del Régimen aplican políticas proteccionistas agresivas frente a la importación de filmes estadounidenses. La conflictiva relación de las productoras de Hollywood con el Régimen franquista no impide su liderazgo en la recaudación en la taquilla ni su influencia en los modos de producción de la cinematografía nacional.

Image rectification for prism-based stereoscopic optical systems

Image rectification is an important stage of digital image processing for three-dimensional (3D) coordinate measurements performed using stereoscopic technique. Rectification minimizes image distortions and radically reduces the calculation time necessary for stereo matching. Calibration of prism-based stereoscopic optical systems using the ray tracing camera model instead of a pinhole one leads to significant reduction of measurement errors, but this model has no single center of projection and does not allow applying conventional rectification techniques. This leads to the necessity of separate calibrations of the pinhole model for image rectification and the ray tracing model for 3D reconstruction. To overcome this contradiction, we propose the rectification technique, which uses the inverse ray tracing to find intersection points of the rays with the intermediate plane in the object space and then projects these points onto image planes of the virtual cameras. The distance to the rectification plane has significant impact on the misalignment of rectified images, so it was analyzed using computer simulation for various distances to the object. The technique has been integrated into the 3D model acquisition algorithm and verified by applying to the images of test and real objects obtained by two different miniature prism-based stereovision systems. For the typical working range 12–30 mm of endoscopic stereo imagers and the single rectification distance of 15 mm, it provides the rectification accuracy better than the accuracy provided by the pinhole rectification technique. Additionally, we have shown that the ray tracing camera model combined with the proposed rectification method can compensate the prism angular displacement around the optical axis, which hinders a correct matching of rectified images. The proposed technique is applicable to many non-central camera models used for catadioptric systems, depth-from-refraction systems and systems using lenses with significant pupil aberrations.

Investigation of optical properties of infitec and active stereo stereoscopic techniques for CAVE-type virtual reality systems

Investigation of optical properties of infitec and active stereo stereoscopic techniques for CAVE-type virtual reality systems

Disparity tuning guided stereoscopic saliency detection for eye fixation prediction

The development of emerging 3D display brings increasing attention of stereoscopic techniques such as quality assessment, re-targeting, and compression of 3D image, that require new saliency detection methods to deal with stereoscopic data. In this paper, we present a disparity tuning guided stereoscopic saliency (DTSS) model which apply the disparity tuning mechanism of visual cortical neurons into visual attention modeling. First, we investigate the rationality of converting features from physical quantity into perception quantity before computing saliency. Second, we discuss the biological principles that depth affects visual attention and consider both absolute and relative depth tuning mechanisms to model visual attention. Then, we propose a diffusion saliency feature combining depth and RGB features. Specifically, we use RGB contrast as primitive labels to diffuse a saliency map for depth map and using depth contrast as primitive labels to diffuse a saliency map for RGB image. Finally, an adaptively weighted fusion method is proposed for the integration of feature maps. Experiments demonstrate that the proposed model performs well against to the state-of-art methods on the task of 3D eye fixation prediction.

Accuracy Assessment of Digital Elevation Model Generated by SAR Stereoscopic Technique Using COSMO-Skymed Data

Radargrammetry technique using the stereoscopic synthetic aperture radar (SAR) images is used for the generation of a digital elevation model (DEM) of a region requires only the amplitude images. SAR stereoscopic technique is analogous to the stereo-photogrammetric technique where the optical stereoscopic images are used for DEM generation. While the advantages of the SAR images are their indifference to atmospheric transparency and solar illumination conditions, the side-looking geometry of the SAR increases the complexity in the SAR stereo analysis. The availability of high spatial and temporal resolution SAR data in recent years has facilitated generation of high-resolution DEM with greater vertical accuracy using radargrammetric technique. In the present study, attempt has been made to generate the DEM of Dehra Dun region, India, from the COSMO-Skymed X-band SAR data-pair acquired at 8 days interval through the radargrammetry technique. Here, radargrammetric orientation approach has been adopted to generate the DEM and various issues and processing steps with the radargrammetry technique have been discussed. The DEM was validated with ground measured elevation values using a differential global positioning system and the root-mean-square error of the DEM was found as 7.3 m. The DEM was compared with the reference DEM of the study area generated from the Cartosat-1 stereo data with a model accuracy of 4 m.

Geometry-based methods for general non-planar perspective projections on curved displays

Curved monitors are getting more and more popular nowadays, due to the immersive sensation they provide to users in front of planar monitors. The display in curved monitors is cylindrical surfaces with significant curvatures, which must be taken into account for an accurate projection of the rendered scene. In this paper, we propose new geometry-based methods for nonlinear projections over cylindrical surfaces (corresponding to the geometry of the curved monitor displays) instead of the traditional planar projections, which produce incorrect results on this kind of screens. The proposed methods allow accurate projections on curved screens, even in the case of non-symmetric view frustum, which is the typical view volume obtained either when stereoscopic techniques are used for creating the illusion of depth or when head-tracking is used and the projection equations must be adapted to the relative position of the user eyes. The proposed methods are designed to be implemented on modern programmable GPUs, and the performance evaluation results show that they easily achieve interactive refresh rates even with complex scenes, while they do not significantly reduce the system performance with respect to the case of planar projection.

Stereoscopic TR PIV measurement and POD analysis of flow behind the turbine prototype of model size

When measuring turbine prototype flow, a number of modes with different flow rates and cavitating vortex rope settings have been measured. The turbulent flow in the draft tube of diameter 240 mm reaches the Reynolds number of 105. The vortex and highly swirling flow is developed in the draft tube. The usage of kHz-order frame rates was necessary to resolve the velocity field. The investigated area in the mixing vessel was examined by the stereoscopic time-resolved PIV technique. Further mode evaluation allows comparison of cross-sectional velocities in the vector map. The Proper orthogonal decomposition analysis was applied on 3D vector maps, those including u, v, w velocity compounds. In the selected regimes – operating points with volume flow rate 97 l/sec and 114 l/sec, the greatest risk of transition to cavitation mode was identified, so they were studied in detail.

The effect of reverberation and audio spatialization on egocentric distance estimation of objects in stereoscopic virtual reality

It has been reported by numerous studies on distance perception in VR that a compression of visual space occurs in virtual environments presented using stereoscopic techniques. Other studies have shown that modified environmental auditory cues can affect egocentric spatial perception and that increased order of modality improved the experience of immersive media. Work was conducted to measure the effect of spatialized acoustic cues on egocentric distance estimation in head mounted display VR. Results suggest that the although early reflection content was not found to have significant effect on estimation of distance, presence of reverberation increases the perception of distance for objects further than 5m from the user and can compensate for the spatial compression observed in the use of stereoscopic VR.

Experimental evaluation of the airflow behaviour in horizontal and vertical Open Joint Ventilated Facades using Stereo-PIV

This research focuses on the analysis of Open Joint Ventilated Facades with both vertical and horizontal apertures. The fluid-dynamic and thermal behaviour of this passive system is experimentally evaluated at the horizontal and vertical joints. The experimental study is performed considering no wind, and solar radiation corresponding to 4 × 108, 9 × 108 and 1 × 109 Rayleigh values. The experimental analysis of the fluid-dynamic behaviour in the facade is conducted through the set-up and optimization of a Stereo-PIV facility. The stereoscopic technique is based on particle image velocimetry in fluids, calculating three dimensional vector velocity fields along selected surfaces inside the ventilated air cavity. Based on the instantaneous measured field velocity it is possible to calculate other factors such as the average field velocity and the turbulence intensity, or to identify the main turbulence structures in the flow. The results indicate that the mean velocity and the turbulence quantities are enhanced by buoyancy. It has also been observed that the instabilities in the flow increase with the Ra numbers. The airflow rate through the facade joints has been calculated. Additionally, the air temperature inside the ventilated cavity as well as the surface temperature of the panels has been monitored and compared.

Depth Perception and the History of Three-Dimensional Art: Who Produced the First Stereoscopic Images?

The history of the expression of three-dimensional structure in art can be traced from the use of occlusion in Palaeolithic cave paintings, through the use of shadow in classical art, to the development of perspective during the Renaissance. However, the history of the use of stereoscopic techniques is controversial. Although the first undisputed stereoscopic images were presented by Wheatstone in 1838, it has been claimed that two sketches by Jacopo Chimenti da Empoli (c. 1600) can be to be fused to yield an impression of stereoscopic depth, while others suggest that Leonardo da Vinci’s Mona Lisa is the world’s first stereogram. Here, we report the first quantitative study of perceived depth in these works, in addition to more recent works by Salvador Dalí. To control for the contribution of monocular depth cues, ratings of the magnitude and coherence of depth were recorded for both stereoscopic and pseudoscopic presentations, with a genuine contribution of stereoscopic cues revealed by a difference between these scores. Although effects were clear for Wheatstone and Dalí’s images, no such effects could be found for works produced earlier. As such, we have no evidence to reject the conventional view that the first producer of stereoscopic imagery was Sir Charles Wheatstone.

Stereoscopic Particle Image Velocimetry Investigation of the Bidirectional Natural Convection Flow Through a Horizontal Vent

An experimental study investigates the natural convection flow through a horizontal ceiling vent of a fire compartment. This flow is governed by the buoyancy forces and the friction forces, and is bidirectional. The orifice used is of circular cross section and is characterized by the aspect ratio L/D of its thickness L over its diameter D. The reduced scale apparatus consist of two superimposed compartments of $$1.5 \times 1 \times 1 \, \mathrm{m}^3$$ for the lower and $$1 \times 1 \times 1 \, \mathrm{m}^3$$ for the upper. These two rooms are connected by a 0.038 m length circular orifice with different diameters available ( $$ D \in [63.5, \, 76.2, \, 127, \, 152.4, \, 190.5, \, 260$$ mm]). For the study of natural convection, only the lower compartment is used; the upper compartment is left at atmospheric conditions by removing all its walls. The temperature gradient ( $$\Delta T \approx 50^\circ $$ C between the bottom and the top of the orifice) is generated by a 2 kW electrical resistor located in the lower compartment. This electrical resistor makes it possible to generate, without mass inlet, a plume with no soot and to reach a thermal steady state in the “fire room”. The optical stereoscopic particle image velocimetry measurement technique provides the velocity field through the opening for different diameters. This technique, based on the finding of the displacement of a set of particles between two consecutive snapshots of a seeded fluid, makes it possible to obtain all three components of the velocity vector field by non-intrusive measurement. The use of this technique is a novelty for such vent flows and allows accessing information not only on the variation of the flow rate but also on the distribution of the fluids moving upward and downward through the orifice. Despite an unsteady dynamic regime, the analysis of averaged fields shows a geometrical organization of the bidirectional flow through the orifice, with a central area occupied by the hot fluid flowing upward and a peripheral zone where the cold fluid flows downward. The flow section occupancy ratio reverses with the extrema of flow velocities, for $$L/D \approx 0.41$$ .