23 research outputs found

    3D light field LED wall

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    The quality of experience of emerging display technologies

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    As new display technologies emerge and become part of everyday life, the understanding of the visual experience they provide becomes more relevant. The cognition of perception is the most vital component of visual experience; however, it is not the only cognition that contributes to the complex overall experience of the end-user. Expectations can create significant cognitive bias that may even override what the user genuinely perceives. Even if a visualization technology is somewhat novel, expectations can be fuelled by prior experiences gained from using similar displays and, more importantly, even a single word or an acronym may induce serious preconceptions, especially if such word suggests excellence in quality. In this interdisciplinary Ph.D. thesis, the effect of minimal, one-word labels on the Quality of Experience (QoE) is investigated in a series of subjective tests. In the studies carried out on an ultra-high-definition (UHD) display, UHD video contents were directly compared to their HD counterparts, with and without labels explicitly informing the test participants about the resolution of each stimulus. The experiments on High Dynamic Range (HDR) visualization addressed the effect of the word “premium” on the quality aspects of HDR video, and also how this may affect the perceived duration of stalling events. In order to support the findings, additional tests were carried out comparing the stalling detection thresholds of HDR video with conventional Low Dynamic Range (LDR) video. The third emerging technology addressed by this thesis is light field visualization. Due to its novel nature and the lack of comprehensive, exhaustive research on the QoE of light field displays and content parameters at the time of this thesis, instead of investigating the labeling effect, four phases of subjective studies were performed on light field QoE. The first phases started with fundamental research, and the experiments progressed towards the concept and evaluation of the dynamic adaptive streaming of light field video, introduced in the final phase

    The key performance indicators of projection-based light field visualization

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    At the time of writing this paper, light field visualization has entered the professional environments in the industry and has also become commercially available. It is not yet present on the consumer market, however, and its widespread emergence is expected in the following decade, with affordable end user devices and a vast variety of applications and contents. The successful integration of this technology into people’s everyday lives essentially depends on the visualization quality, which is achieved through excellence in terms of the key performance indicators of the display system and the content it visualizes. In this paper, the key performance indicators of light field visualization for both display and content are reviewed. Beyond providing a comprehensive review of the vital parameters of visualization quality, this paper discusses the ongoing and future relevant research efforts, demonstrates the practical uses of the technology, highlights certain dependencies between the indicators, and addresses issues of perceived quality with regard to the lack of compliance with the requirements and visual thresholds

    Optimized 3D Scene Rendering on Projection-Based 3D Displays

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    We address the problem of 3D scene rendering on projection-based light field displays and optimizing the input display images to obtain the best possible visual output. We discuss a display model comprising a set of projectors, an anisotropic diffuser and a viewing manifold. Based on this model, we render an initial set of projector images to be further optimized for the best perception at a specified set of viewing positions. We propose a least squares method, which minimizes the channel-wise color difference between the generated images for different viewer positions, and their ground-true counterparts. We formulate a constrained optimization problem and solve it iteratively by the descent method.acceptedVersionPeer reviewe

    Methods for Light Field Display Profiling and Scalable Super-Multiview Video Coding

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    Light field 3D displays reproduce the light field of real or synthetic scenes, as observed by multiple viewers, without the necessity of wearing 3D glasses. Reproducing light fields is a technically challenging task in terms of optical setup, content creation, distributed rendering, among others; however, the impressive visual quality of hologramlike scenes, in full color, with real-time frame rates, and over a very wide field of view justifies the complexity involved. Seeing objects popping far out from the screen plane without glasses impresses even those viewers who have experienced other 3D displays before.Content for these displays can either be synthetic or real. The creation of synthetic (rendered) content is relatively well understood and used in practice. Depending on the technique used, rendering has its own complexities, quite similar to the complexity of rendering techniques for 2D displays. While rendering can be used in many use-cases, the holy grail of all 3D display technologies is to become the future 3DTVs, ending up in each living room and showing realistic 3D content without glasses. Capturing, transmitting, and rendering live scenes as light fields is extremely challenging, and it is necessary if we are about to experience light field 3D television showing real people and natural scenes, or realistic 3D video conferencing with real eye-contact.In order to provide the required realism, light field displays aim to provide a wide field of view (up to 180°), while reproducing up to ~80 MPixels nowadays. Building gigapixel light field displays is realistic in the next few years. Likewise, capturing live light fields involves using many synchronized cameras that cover the same display wide field of view and provide the same high pixel count. Therefore, light field capture and content creation has to be well optimized with respect to the targeted display technologies. Two major challenges in this process are addressed in this dissertation.The first challenge is how to characterize the display in terms of its capabilities to create light fields, that is how to profile the display in question. In clearer terms this boils down to finding the equivalent spatial resolution, which is similar to the screen resolution of 2D displays, and angular resolution, which describes the smallest angle, the color of which the display can control individually. Light field is formalized as 4D approximation of the plenoptic function in terms of geometrical optics through spatiallylocalized and angularly-directed light rays in the so-called ray space. Plenoptic Sampling Theory provides the required conditions to sample and reconstruct light fields. Subsequently, light field displays can be characterized in the Fourier domain by the effective display bandwidth they support. In the thesis, a methodology for displayspecific light field analysis is proposed. It regards the display as a signal processing channel and analyses it as such in spectral domain. As a result, one is able to derive the display throughput (i.e. the display bandwidth) and, subsequently, the optimal camera configuration to efficiently capture and filter light fields before displaying them.While the geometrical topology of optical light sources in projection-based light field displays can be used to theoretically derive display bandwidth, and its spatial and angular resolution, in many cases this topology is not available to the user. Furthermore, there are many implementation details which cause the display to deviate from its theoretical model. In such cases, profiling light field displays in terms of spatial and angular resolution has to be done by measurements. Measurement methods that involve the display showing specific test patterns, which are then captured by a single static or moving camera, are proposed in the thesis. Determining the effective spatial and angular resolution of a light field display is then based on an automated analysis of the captured images, as they are reproduced by the display, in the frequency domain. The analysis reveals the empirical limits of the display in terms of pass-band both in the spatial and angular dimension. Furthermore, the spatial resolution measurements are validated by subjective tests confirming that the results are in line with the smallest features human observers can perceive on the same display. The resolution values obtained can be used to design the optimal capture setup for the display in question.The second challenge is related with the massive number of views and pixels captured that have to be transmitted to the display. It clearly requires effective and efficient compression techniques to fit in the bandwidth available, as an uncompressed representation of such a super-multiview video could easily consume ~20 gigabits per second with today’s displays. Due to the high number of light rays to be captured, transmitted and rendered, distributed systems are necessary for both capturing and rendering the light field. During the first attempts to implement real-time light field capturing, transmission and rendering using a brute force approach, limitations became apparent. Still, due to the best possible image quality achievable with dense multi-camera light field capturing and light ray interpolation, this approach was chosen as the basis of further work, despite the massive amount of bandwidth needed. Decompression of all camera images in all rendering nodes, however, is prohibitively time consuming and is not scalable. After analyzing the light field interpolation process and the data-access patterns typical in a distributed light field rendering system, an approach to reduce the amount of data required in the rendering nodes has been proposed. This approach, on the other hand, requires rectangular parts (typically vertical bars in case of a Horizontal Parallax Only light field display) of the captured images to be available in the rendering nodes, which might be exploited to reduce the time spent with decompression of video streams. However, partial decoding is not readily supported by common image / video codecs. In the thesis, approaches aimed at achieving partial decoding are proposed for H.264, HEVC, JPEG and JPEG2000 and the results are compared.The results of the thesis on display profiling facilitate the design of optimal camera setups for capturing scenes to be reproduced on 3D light field displays. The developed super-multiview content encoding also facilitates light field rendering in real-time. This makes live light field transmission and real-time teleconferencing possible in a scalable way, using any number of cameras, and at the spatial and angular resolution the display actually needs for achieving a compelling visual experience

    An interactive 3D medical visualization system based on a light field display

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    This paper presents a prototype medical data visualization system exploiting a light field display and custom direct volume rendering techniques to enhance understanding of massive volumetric data, such as CT, MRI, and PET scans. The system can be integrated with standard medical image archives and extends the capabilities of current radiology workstations by supporting real-time rendering of volumes of potentially unlimited size on light field displays generating dynamic observer-independent light fields. The system allows multiple untracked naked-eye users in a sufficiently large interaction area to coherently perceive rendered volumes as real objects, with stereo and motion parallax cues. In this way, an effective collaborative analysis of volumetric data can be achieved. Evaluation tests demonstrate the usefulness of the generated depth cues and the improved performance in understanding complex spatial structures with respect to standard techniques.883-893Pubblicat

    Camera animation for immersive light field imaging

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    Among novel capture and visualization technologies, light field has made significant progress in the current decade, bringing closer its emergence in everyday use cases. Unlike many other forms of 3D displays and devices, light field visualization does not depend on any viewing equipment. Regarding its potential use cases, light field is applicable to both cinematic and interactive contents. Such contents often rely on camera animation, which is a frequent tool for the creation and presentation of 2D contents. However, while common 3D camera animation is often rather straightforward, light field visualization has certain constraints that must be considered before implementing any variation of such techniques. In this paper, we introduce our work on camera animation for light field visualization. Different types of conventional camera animation were applied to light field contents, which produced an interactive simulation. The simulation was visualized and assessed on a real light field display, the results of which are presented and discussed in this paper. Additionally, we tested different forms of realistic physical camera motion in our study, and based on our findings, we propose multiple metrics for the quality evaluation of light field visualization in the investigated context and for the assessment of plausibility

    Depth of field guided visualisation on light field displays

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    Light field displays are capable of realistic visualization of arbitrary 3D content. However, due to the finite number of light rays reproduced by the display, its bandwidth is limited in terms of angular and spatial resolution. Consequently, 3D content that falls outside of that bandwidth will cause aliasing during visualization. Therefore, a light field to be visualized must be properly preprocessed. In this thesis, we propose three methods that properly filter the parts in the input light field that would cause aliasing. First method is based on a 2D FIR circular filter that is applied over the 4D light field. Second method utilizes the structured nature of the epipolar plane images representing the light field. Third method adopts real-time multi-layer depth-of-field rendering using tiled splatting. We also establish a connection between lens parameters in the proposed depth-of-field rendering and the display’s bandwidth in order to determine the optimal blurring amount. As we prepare light field for light field displays, a stage is added to the proposed real-time rendering pipeline that simultaneously renders adjacent views. The rendering performance of the proposed methods is demonstrated on Holografika’s Holovizio 722RC projection-based light field display
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