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Realistic visualizations are abundantly used in digital education. However, the use of realism is still thought to risk a cognitive overload due to excessive details. Moreover, it is still not precisely known whether there is an optimal level of realism that benefits learners the most. In two experimental studies, different versions of anatomical visualizations were compared regarding their effects on retention performance and the subjective cognitive load experienced during learning. In Experiment 1 (n = 73), four visualizations with minor variations in the geometry and shading of the model featured in the visualizations were used. Although neither the level of detail in the geometry nor the realism of the shading resulted in significant differences, a detailed model with simplified shading elicited the highest retention scores descriptively. In Experiment 2 (n = 156), a schematic visualization was compared with an "idealized" model featuring only simplified shading and a highly realistic rendering. There most realistic version elicited the highest retention scores, but also the highest cognitive load ratings. Taken together, the results suggest that the optimal level of realism might lie on the more realistic end of the spectrum for learning tasks focused on the memorization of shapes that are assessed using image-based tests. [ABSTRACT FROM AUTHOR]

In advanced medical technology, rendering methods plays an essential role in enhancing the accuracy of mitral valve abnormalities detection and replacement procedures especially in the process of virtual surgery. Consequently, the choice of rendering methods is very much important for real-time visualization of mitral valve echocardiography. This study compares two types of rendering methods in virtual reality visualization: Surface Rendering and Volume Rendering. Specifically, two rendering algorithms including Ray Casting and Marching Cubes were implemented and compared with respect to the rendering speed and interaction. These algorithms were implemented in unity platform to visualize the cardiac echo images in virtual reality. The methodologies, merits and demerits of these algorithms were discussed in detail. Based on the experimental results, rendering method can be determined according to the requirements of virtual mitral valve replacement surgery. [ABSTRACT FROM AUTHOR]

Convolution neural networks usually require large labeled data-sets to construct accurate models. However, in many real-world scenarios, such as global illumination, labeling data are a time-consuming and costly human intelligent task. Semi-supervised learning methods leverage this issue by making use of a small labeled data-set and a larger set of unlabeled data. In this paper, our contributions focus on the development of a robust algorithm that combines active and deep semi-supervised convolution neural network to reduce labeling workload and to accelerate convergence in case of real-time global illumination. While the theoretical concepts of photo-realistic rendering are well understood, the increased need for the delivery of highly dynamic interactive content in vast virtual environments has increased recently. Particularly, the quality measure of computer-generated images is of great importance. The experiments are conducted on global illumination scenes which contain diverse distortions. Compared with human psycho-visual thresholds, the good consistency between these thresholds and the learning models quality measures can been seen. A comparison has also been made with SVM and other state-of-the-art deep learning models. We do transfer learning by running the convolution base of these models over our image set. Then, we use the output features of the convolution base as input to retrain the parameters of the fully connected layer. The obtained results show that our proposed method provides promising efficiency in terms of precision, time complexity, and optimal architecture. [ABSTRACT FROM AUTHOR]

Recently, methods and devices that simultaneously utilize two or more tactile feedback types have been proposed for more immersive interaction with virtual objects. However, the masking effect, which makes us less sensitive to various stimuli presented at the same time, has scarcely been explored. In this study, we propose a novel tactile rendering algorithm that can eliminate the mutual masking effect at the user's sensation level, when mechanical vibration and electrovibration are applied simultaneously. First, the masking functions of the two stimuli were investigated for various stimulus combinations. Based on these, a generalized form of the masking function was derived. We then tested and confirmed that the proposed algorithm, which calculates the required stimulus intensity to compensate for the mutual masking effect, could render the arbitrary stimulus intensity desired to be perceived by the users. The results of the user test revealed that the proposed rendering algorithm significantly improved the virtual object recognition rate by approximately 23% when geometry and texture were presented jointly. This finding suggests principal guidelines for the combined use of mechanical vibration and electrovibration, as well as for other combinations of different tactile feedback types. [ABSTRACT FROM AUTHOR]

Facial aging is an important problem of face recognition in missing children and automatic template update. As aging is a temporal process, it alters the facial appearance of the individuals. The sources of variations in facial appearance are caused by wrinkles (under eyes, forehead, around lips, and jawline), facial growth (cranial size and skull), and skin tone. The other factors such as health, lifestyle, and gender also impose variations in the aging process. Therefore, predicting facial aging with considering all those factors is a very difficult task. We present our 3D gender-specific aging model which automatically produces simulated images at age y by taking only one input image at age x irrespective of the pose and lighting conditions. The gender-specific aging model is constructed by various datasets (FG-NET, PCSO, Celebrities, BROWNS, Private), and its quality is evaluated with respect to various combinations of the datasets. We further fine-tune the aging model by changing the length of shape and texture eigenvectors and examine how these parameters affect the simulation results. Comparisons of the simulation results with state-of-the-art approaches as well as ground truth images demonstrate the effectiveness of the proposed methods. The subjective and objective evaluations are also carried out which emphasize the potential of our proposed gender-specific 3D aging model. [ABSTRACT FROM AUTHOR]

Pancreatic cancer is the third most common cause of cancer death and CT is the most commonly used modality for the initial evaluation of suspected pancreatic cancer. Post-processing of CT data into 2D multiplanar and 3D reconstructions has been shown to improve tumor visualization and assessment of tumor resectability compared to axial slices, and is considered the standard of care. Cinematic rendering is a new 3D-rendering technique that produces photorealistic images, and it has the potential to more accurately depict anatomic detail compared to traditional 3D reconstruction techniques. The purpose of this article is to describe the potential application of CR to imaging of pancreatic neoplasms. CR has the potential to improve visualization of subtle pancreatic neoplasms, differentiation of solid and cystic pancreatic neoplasms, assessment of local tumor extension and vascular invasion, and visualization of metastatic disease. [ABSTRACT FROM AUTHOR]

Abstract Polar codes recently received high attention by researchers as proven to approach channel capacity at higher codeword length. However, the decoding latency grows significantly with codeword length, rendering implementation for latency constrained applications impossible. To tackle this problem, this paper proposes a polar decoder architecture based on radix-4 processing units with a special last stage processing unit to decode up to 16 bits in the same clock. In addition, it proposes decoding extended special subcodes to reduce latency. Moreover, it uses partial sum look-ahead technique, resulting in a high throughput low latency decoding architecture. [ABSTRACT FROM AUTHOR]

Highlights • We propose a new disparity control method for visual comfort in multiview displays. • Foreground object extraction is applied for free disparity adjustment and natural texture synthesis. • An effective and efficient exemplar-based inpainting algorithm is proposed. • Translucent cracks are removed by using segmentation results. Abstract Among the rapidly growing three-dimensional technologies, multiview displays have drawn great research interests in three-dimensional television due to their adaption to the motion parallax and wider viewing angles. However, multiview displays still suffer from dazzling discomfort on the border of viewing zones. Leveraging on the separability of scene via foreground segmentation, we propose a novel virtual view synthesis method for depth-image-based rendering to alleviate the discomfort. Foreground objects of interest are extracted to segment the whole image into multiple layers, which are further warped to the virtual viewpoint in order. To alleviate the visual discomfort, global disparity adjustments and local depth control are performed for specific objects in each layer. For the post-processing, we improve an exemplar-based inpainting algorithm to tackle the disoccluded areas. Experimental results demonstrate that our method achieves effective disparity control and generates high-quality virtual view images. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new technique to incorporate recent adaptive rendering approaches built upon local regression theory into a gradient‐domain path tracing framework, in order to achieve high‐quality rendering results. Our method aims to reduce random artifacts introduced by random sampling on image colors and gradients. Our high‐level approach is to identify a feature image from noisy gradients, and pass the image to an existing local regression based adaptive method so that adaptive sampling and reconstruction using our feature can boost the performance of gradient‐domain rendering. To fulfill our idea, we derive an ideal feature in the form of image gradients and propose an estimation process for the ideal feature in the presence of noise in image gradients. We demonstrate that our integrated adaptive solution leads to performance improvement for a gradient‐domain path tracer, by seamlessly incorporating recent adaptive sampling and reconstruction strategies through our estimated feature. [ABSTRACT FROM AUTHOR]

Abstract: We propose an elemental image array (EIA) generation method by using an optimized depth image‐based rendering (DIBR) algorithm. In this method, the EIA is synthesized by the reference and virtual viewpoint elemental images, and the virtual viewpoint elemental images at the given locations are generated by DIBR algorithm. We optimize the existing DIBR algorithm by adaptively repairing the warped depth images in the processing part and extend the generation dimension of the virtual viewpoint elemental images from one dimension to two dimensions. The optimized DIBR algorithm can effectively solve the problem: the low quality of virtual viewpoint elemental images caused by discontinuous depth values and disocclusion regions. We also implement the generations of virtual viewpoint elemental images and EIA in graph processing unit to reduce the time cost. Experimental results show that the proposed method can not only improve the quality of the virtual viewpoint images but also accelerate the generations of the virtual viewpoint elemental images and EIA. [ABSTRACT FROM AUTHOR]

A focused plenoptic camera can effectively transform angular and spatial information to yield a refocused rendered image with high resolution. However, choosing a proper patch size poses a significant problem for the image-rendering algorithm. By using a spatial frequency response measurement, a method to obtain a suitable patch size is presented. By evaluating the spatial frequency response curves, the optimized patch size can be obtained quickly and easily. Moreover, the range of depth over which images can be rendered without artifacts can be estimated. Experiments show that the results of the image rendered based on frequency response measurement are in accordance with the theoretical calculation, which indicates that this is an effective way to determine the patch size. This study may provide support to light-field image rendering. [ABSTRACT FROM AUTHOR]

In this study we examined whether grouping by luminance similarity and grouping by connectedness can occur in the absence of visual awareness, using a priming paradigm and two methods to render the prime invisible, CFS and sandwich masking under matched conditions. For both groupings, significant response priming effects were observed when the prime was reported invisible under sandwich masking, but none were obtained under CFS. These results provide evidence for unconscious grouping, converging with previous findings showing that visual awareness is not essential for certain perceptual organization processes to occur. They are also consistent with findings indicating that processing during CFS is limited, and suggest the involvement of higher visual areas in perceptual organization. Moreover, these results demonstrate that whether a process can occur without awareness is dependent on the level at which the suppression induced by the method used for rendering the stimulus inaccessible to awareness takes place. [ABSTRACT FROM AUTHOR]

The production of clinical waste is an inevitable consequence of rendering health services, including hazardous infectious clinical waste containing live pathogenic microorganisms, which can be the potential source of infections and infectious diseases. For this reason, the management of waste collected during rendering health services most of all requires responsibility for the security of both patients and staff on the part of the managers of healthcare-institutions. The results of hospital inspections in the field of clinical-waste management conducted by the Voivodeship Sanitary Inspection in Lublin, which were made available for the purpose of this paper, have shown numerous irregularities concerning the management of hazardous clinical waste. Most of the irregularities involved the condition of premises and the temporary storage of clinical waste. [ABSTRACT FROM AUTHOR]

The discriminative ability of dictionary learning algorithms plays a crucial role in various computer vision applications, particularly in visual object tracking. In this paper, a novel visual tracking algorithm based on an online discriminative dictionary learning technique is proposed. The proposed method incorporates target and background information into dictionary learning in order to separate the target-of-interest from a cluttered background effectively. The dictionary thus learnt, can ensure that each class-specific sub-dictionary has a good representation of the samples associated with its own class and a poor representation of the other classes. In contrast to other dictionary learning mechanisms, the proposed method also introduces an error term that aims to capture outliers (e.g., noise and occlusion) and minimize its effect on tracking. Furthermore, by optimizing a constrained objective function, the learnt dictionary is rendered robust and discriminative, thereby resulting in an accurate tracking framework that can efficiently separate the target from the background. Finally, an effective and simple observation likelihood function based on the reconstruction errors from both positive and negative templates is designed to achieve better tracking performance. Experimental results on a publicly available benchmark dataset demonstrate that the proposed tracking algorithm performs better than several baseline trackers. [ABSTRACT FROM AUTHOR]

We present a signal-processing framework for image-assisted geometry measurement in the image-based rendering (IBR). We study the utilized geometry information and estimating minimum sampling rate of the IBR. Our method combines decomposing a complex scene geometry into a collection of simpler structures on a block-by-block basis. The automatic simpler structure selection can be interactively refined by detected single salient points. In this manner, we reduce the spectral analysis problem of an irregular object to that of a simpler structure. Predictions on the frequency content can then be used to control the sampling rate. This extends previous work in which the IBR sampling is analyzed and estimated for nonuniform sampling. Extensive experimental evaluation demonstrates that our geometry simplification method significantly outperforms competing algorithms. Additionally, the minimum sampling rate of the IBR necessary for alias-free rendering will be reduced as the number of simpler structures increases. [ABSTRACT FROM PUBLISHER]

We study Markov Chain Monte Carlo (MCMC) methods operating in primary sample space and their interactions with multiple sampling techniques. We observe that incorporating the sampling technique into the state of the Markov Chain, as done in Multiplexed Metropolis Light Transport, impedes the ability of the chain to properly explore the path space, as transitions between sampling techniques lead to disruptive alterations of path samples. To address this issue, we reformulate Multiplexed MLT in the Reversible Jump MCMC framework (RJMCMC) and introduce inverse sampling techniques that turn light paths into the random numbers that would produce them. This allows us to formulate a novel perturbation that can locally transition between sampling techniques without changing the geometry of the path, and we derive the correct acceptance probability using RJMCMC. We investigate how to generalize this concept to non-invertible sampling techniques commonly found in practice, and introduce probabilistic inverses that extend our perturbation to cover most sampling methods found in light transport simulations. Our theory reconciles the inverses with RJMCMC yielding an unbiased algorithm, which we call Reversible Jump MLT. We verify the correctness of our implementation in canonical and practical scenarios and demonstrate improved temporal coherence, decrease in structured artifacts, and faster convergence on a wide variety of scenes. [ABSTRACT FROM AUTHOR]

We propose a novel framework of haptic rendering and interactive simulation, which, by exploiting midpoint time integration, that is known for its superior energy-conserving property but has not yet been adopted for haptics and interactive simulation, can enforce discrete-time passivity of the simulation effectively in practice, while retaining real-time interactivity due to its being non-iterative. We derive this passive midpoint integration (PMI) simulation for mechanical systems both in maximal coordinates (i.e. in SE(3)) and in generalized coordinates (i.e. in ℜ n ), with some potential actions as well to implement joint articulation, constraints, compliance, and so on. We also fully incorporate multi-point Coulomb frictional contact into them via the PMI-LCP (linear complementarity problem) formulation. The proposed PMI-based simulation framework is applied to some illustrative examples to demonstrate its advantages: (1) haptic rendering of a peg-in-hole task, where very light/stiff articulated objects can be simulated with multi-point contact; (2) haptic interaction with a flexible beam, where marginally stable/lossless behavior (i.e. vibration) can be stably emulated; and (3) under-actuated tendon-driven hand grasping, where mixed maximal-generalized coordinates are used with very light/stiff fingers. [ABSTRACT FROM AUTHOR]

Purpose Arrhythmias can be treated by ablating the heart tissue in the regions of abnormal contraction. The current clinical standard provides electroanatomic 3-D maps to visualize the electrical activation and locate the arrhythmogenic sources. However, the procedure is time-consuming and invasive. Electromechanical wave imaging is an ultrasound-based noninvasive technique that can provide 2-D maps of the electromechanical activation of the heart. In order to fully visualize the complex 3-D pattern of activation, several 2-D views are acquired and processed separately. They are then manually registered with a 3-D rendering software to generate a pseudo-3-D map. However, this last step is operator-dependent and time-consuming. Methods This paper presents a method to generate a full 3-D map of the electromechanical activation using multiple 2-D images. Two canine models were considered to illustrate the method: one in normal sinus rhythm and one paced from the lateral region of the heart. Four standard echographic views of each canine heart were acquired. Electromechanical wave imaging was applied to generate four 2-D activation maps of the left ventricle. The radial positions and activation timings of the walls were automatically extracted from those maps. In each slice, from apex to base, these values were interpolated around the circumference to generate a full 3-D map. Results In both cases, a 3-D activation map and a cine-loop of the propagation of the electromechanical wave were automatically generated. The 3-D map showing the electromechanical activation timings overlaid on realistic anatomy assists with the visualization of the sources of earlier activation (which are potential arrhythmogenic sources). The earliest sources of activation corresponded to the expected ones: septum for the normal rhythm and lateral for the pacing case. Conclusions The proposed technique provides, automatically, a 3-D electromechanical activation map with a realistic anatomy. This represents a step towards a noninvasive tool to efficiently localize arrhythmias in 3-D. [ABSTRACT FROM AUTHOR]

We present a novel method to optimize the attenuation of light for the single scattering model in direct volume rendering. A common problem of single scattering is the high dynamic range between lit and shadowed regions due to the exponential attenuation of light along a ray. Moreover, light is often attenuated too strong between a sample point and the camera, hampering the visibility of important features. Our algorithm employs an importance function to selectively illuminate important structures and make them visible from the camera. With the importance function, more light can be transmitted to the features of interest, while contextual structures cast shadows which provide visual cues for perception of depth. At the same time, more scattered light is transmitted from the sample point to the camera to improve the primary visibility of important features. We formulate a minimization problem that automatically determines the extinction along a view or shadow ray to obtain a good balance between sufficient transmittance and attenuation. In contrast to previous approaches, we do not require a computationally expensive solution of a global optimization, but instead provide a closed-form solution for each sampled extinction value along a view or shadow ray and thus achieve interactive performance. [ABSTRACT FROM AUTHOR]

We present a new approach to rendering a geometrically-correct user-perspective view for a magic lens interface, based on leveraging the gradients in the real world scene. Our approach couples a recent gradient-domain image-based rendering method with a novel semi-dense stereo matching algorithm. Our stereo algorithm borrows ideas from PatchMatch, and adapts them to semi-dense stereo. This approach is implemented in a prototype device build from off-the-shelf hardware, with no active depth sensing. Despite the limited depth data, we achieve high-quality rendering for the user-perspective magic lens. [ABSTRACT FROM AUTHOR]

Rendering translucent materials with physically based Monte Carlo methods tends to be computationally expensive due to the long chains of volumetric scattering interactions. In the case of strongly forward scattering materials, the problem gets compounded since each scattering interaction becomes highly anisotropic and near-specular. Various well-known approaches try to avoid the resulting sampling problem through analytical approximations based on diffusion theory. Although these methods are computationally efficient, their assumption of diffusive, isotropic scattering can lead to considerable errors when rendering forward scattering materials, even in the optically dense limit. In this paper, we present an analytical subsurface scattering model, derived with the explicit assumption of strong forward scattering. Our model is not based on diffusion theory, but follows from a connection that we identified between the functional integral formulation of radiative transport and the partition function of a worm-like chain in polymer physics. Our resulting model does not need a separate Monte Carlo solution for unscattered or single-scattered contributions, nor does it require ad-hoc regularization procedures. It has a single singularity by design, corresponding to the initial unscattered propagation, which can be accounted for by the extensive analytical importance sampling scheme that we provide. Our model captures the full behaviour of forward scattering media, ranging from unscattered straight-line propagation to the fully diffusive limit. Moreover, we derive a novel forward scattering BRDF as limiting case of our subsurface scattering model, which can be used in a level of detail hierarchy. We show how our model can be integrated in existing Monte Carlo rendering algorithms, and make comparisons to previous approaches. [ABSTRACT FROM AUTHOR]

In this paper we present a web-based software solution to the problem of implementing real-time collaborative neuroimage visualization. In both clinical and research settings, simple and powerful access to imaging technologies across multiple devices is becoming increasingly useful. Prior technical solutions have used a server-side rendering and push-to-client model wherein only the server has the full image dataset. We propose a rich client solution in which each client has all the data and uses the Google Drive Realtime API for state synchronization. We have developed a small set of reusable client-side object-oriented JavaScript modules that make use of the XTK toolkit, a popular open-source JavaScript library also developed by our team, for the in-browser rendering and visualization of brain image volumes. Efficient realtime communication among the remote instances is achieved by using just a small JSON object, comprising a representation of the XTK image renderers' state, as the Google Drive Realtime collaborative data model. The developed open-source JavaScript modules have already been instantiated in a web-app called MedView, a distributed collaborative neuroimage visualization application that is delivered to the users over the web without requiring the installation of any extra software or browser plugin. This responsive application allows multiple physically distant physicians or researchers to cooperate in real time to reach a diagnosis or scientific conclusion. It also serves as a proof of concept for the capabilities of the presented technological solution. [ABSTRACT FROM AUTHOR]

Quasi-Monte Carlo (QMC) sampling has been developed for integration over $$[0,1]^s$$ where it has superior accuracy to Monte Carlo (MC) for integrands of bounded variation. Scrambled net quadrature allows replication-based error estimation for QMC with at least the same accuracy and for smooth enough integrands even better accuracy than plain QMC. Integration over triangles, spheres, disks and Cartesian products of such spaces is more difficult for QMC because the induced integrand on a unit cube may fail to have the desired regularity. In this paper, we present a construction of point sets for numerical integration over Cartesian products of s spaces of dimension d, with triangles ( $$d=2$$ ) being of special interest. The point sets are transformations of randomized ( t, m, s)-nets using recursive geometric partitions. The resulting integral estimates are unbiased, and their variance is o(1 / n) for any integrand in $$L^2$$ of the product space. Under smoothness assumptions on the integrand, our randomized QMC algorithm has variance $$O(n^{-1 - 2/d} (\log n)^{s-1})$$ , for integration over s-fold Cartesian products of d-dimensional domains, compared to $$O(n^{-1})$$ for ordinary MC. [ABSTRACT FROM AUTHOR]

This article approaches binaural interactive environments from an artistic research perspective. Beyond content production, an aesthetic reflection of binaural media requires pervasive access to digital processing means and ways to employ them in composition. However, most conventional workflows separate media-specific rendering algorithms from object-based scene authoring. Such a delimitation between binaural engineering and its application restricts transdisciplinary creation that crosses both areas. This article assumes that the full potential of immersive media cannot be explored without investigating technology in the context of aesthetic experience. A case study is presented in which artistic references are regarded together with its technical realization. Contemporary user experience evaluation methods are adopted and refined with reference to the aims of the artist. A subsequent revision of the work is discussed along with implementation adjustments and conceptual alterations. The presented project shall exemplify how artistic research may bridge scholarly investigation and the creative acquirement of media technology beyond its mere application. A point of departure shall be provided for further cross-fertilization between engineering and the arts by identifying mutual implications. [ABSTRACT FROM AUTHOR]

Modern virtual reality simulations require a constant high-frame rate from the rendering engine. They may also require very low latency and stereo images. Previous rendering engines for virtual reality applications have exploited spatial and temporal coherence by using image-warping to re-use previous frames or to render a stereo pair at lower cost than running the full render pipeline twice. However these previous approaches have shown artifacts or have not scaled well with image size. We present a new image-warping algorithm that has several novel contributions: an adaptive grid generation algorithm for proxy geometry for image warping; a low-pass hole-filling algorithm to address un-occlusion; and support for transparent surfaces by efficiently ray casting transparent fragments stored in per-pixel linked lists of an A-Buffer. We evaluate our algorithm with a variety of challenging test cases. The results show that it achieves better quality image-warping than state-of-the-art techniques and that it can support transparent surfaces effectively. Finally, we show that our algorithm can achieve image warping at rates suitable for practical use in a variety of applications on modern virtual reality equipment. [ABSTRACT FROM PUBLISHER]

Large holes are unavoidably generated in depth image based rendering (DIBR) using a single color image and its associated depth map. Such holes are mainly caused by disocclusion, which occurs around the sharp depth discontinuities in the depth map. We propose a divide-and-conquer hole-filling method which refines the background depth pixels around the sharp depth discontinuities to address the disocclusion problem. Firstly, the disocclusion region is detected according to the degree of depth discontinuity, and the target area is marked as a binary mask. Then, the depth pixels located in the target area are modified by a linear interpolation process, whose pixel values decrease from the foreground depth value to the background depth value. Finally, in order to remove the isolated depth pixels, median filtering is adopted to refine the depth map. In these ways, disocclusion regions in the synthesized view are divided into several small holes after DIBR, and are easily filled by image inpainting. Experimental results demonstrate that the proposed method can effectively improve the quality of the synthesized view subjectively and objectively. [ABSTRACT FROM AUTHOR]

Physically based rendering, using path-space formulation of global illumination, has become a standard technique for high-quality computer-generated imagery. Nonetheless, being able to control and edit the resulting picture so that it corresponds to the artist vision is still a tedious trial-and-error process. We show how the manipulation of light transport translates into the path-space integral formulation of the rendering equation. We introduce portals as a path-space manipulation tool to edit and control renderings and show how our editing tool unifies and extends previous work on lighting editing. Portals allow the artist to precisely control the final aspect of the image without modifying neither scene geometry nor lighting setup. According to the setup of two geometric handles and a simple path selection filter, portals capture specific lightpaths and teleport them through 3D space. We implement portals in major path-based algorithms (Photon Mapping, Progressive Photon Mapping and Bi-directional Path Tracing) and demonstrate the wide range of control this technique allows on various lighting effects, from low-frequency color bleeding to high-frequency caustics as well as view-dependent reflections. [ABSTRACT FROM AUTHOR]

While improved visual realism is known to enhance training effectiveness in virtual surgery simulators, the advances on realistic rendering for these simulators is slower than similar simulations for man-made scenes. One of the main reasons for this is that in vivo data is hard to gather and process. In this paper, we propose the analysis of videolaparoscopy data to compute the Bidirectional Reflectance Distribution Function (BRDF) of living organs as an input to physically based rendering algorithms. From the interplay between light and organic matter recorded in video images, we propose the definition of a process capable of establishing the BRDF for inside-the-body organic surfaces. We present a case study around the liver with patient-specific rendering under global illumination. Results show that despite the limited range of motion allowed within the body, the computed BRDF presents a high-coverage of the sampled regions and produces plausible renderings. [ABSTRACT FROM AUTHOR]

With the advances in three-dimensional (3-D) display technology, stereo conversion has attracted much attention as it can alleviate the problem of stereoscopic content shortage. In two-dimensional (2-D) to 3-D conversion, the most difficult and challenging problem is depth estimation from a single image. In order to recover a perceptually plausible depth map from a single image, a depth estimation algorithm based on a data-driven method and depth cues is presented. Based on the human visual system mechanism, which is sensitive to the foreground object, this study classifies the image into one of two classes, i.e., nonobject image and object image, and then leverages different strategies on the basis of image type. The proposed strategies efficiently extract the depth information from different images. Moreover, depth image-based rendering technology is utilized to generate stereoscopic views by combining 2-D images with their depth maps. The proposed method is also suitable for 2-D to 3-D video conversion. Qualitative and quantitative evaluation results demonstrate that the proposed depth estimation algorithm is very effective for generating stereoscopic content and producing visually pleasing and realistic 3-D views. [ABSTRACT FROM AUTHOR]

Several scalable many-light rendering methods have been proposed recently for the efficient computation of global illumination. However, gathering contributions of virtual lights in participating media remains an inefficient and time-consuming task. In this paper, we present a novel sparse sampling and reconstruction method to accelerate the gathering step of the many-light rendering for participating media. Our technique explores the observation that the scattered lightings are usually locally coherent and of low rank even in heterogeneous media. In particular, we first introduce a matrix formation with light segments as columns and eye ray segments as rows, and formulate the gathering step into a matrix sampling and reconstruction problem. We then propose an adaptive matrix column sampling and completion algorithm to efficiently reconstruct the matrix by only sampling a small number of elements. Experimental results show that our approach greatly improves the performance, and obtains up to one order of magnitude speedup compared with other state-of-the-art methods of many-light rendering for participating media. [ABSTRACT FROM AUTHOR]

This paper proposes new models of GPU energy consumption from the perspectives of hardware architects and graphics programmers by performing an architecture-independent analysis of the classical graphics rendering pipeline which is still in widespread use today. The detailed analysis includes graphics rendering workload, memory bandwidth and energy consumption . Although the models are derived from classical 3D pipeline, they are extensible to programmable pipelines. There are many factors that affect the performance and energy consumption of 3D graphics rendering, such as the number of textures, vertex sharing, level of details, and rendering algorithms. The proposed models are validated by our simulation study and used to guide our 3D graphics hardware design and 3D graphics programming in order to optimize performance and energy consumption of our GPU prototypes which have been successfully fabricated in SMIC 0.13 μm CMOS technology. [ABSTRACT FROM AUTHOR]

The depth-image-based rendering (DIBR) algorithms used for 3D video applications introduce new types of artifacts mostly located around the disoccluded regions. As the DIBR algorithms involve geometric transformations, most of them introduce non-uniform geometric distortions affecting the edge coherency in the synthesized images. Such distortions are not handled efficiently by the common image quality assessment metrics which are primarily designed for other types of distortions. In order to better deal with specific geometric distortions in the DIBR-synthesized images, we propose a full-reference metric based on multi-scale image decomposition applying morphological filters. Using non-linear morphological filters in multi-scale image decomposition, important geometric information such as edges is maintained across different resolution levels. Edge distortion between the multi-scale representation subbands of the reference image and the DIBR-synthesized image is measured precisely using mean squared error. In this way, areas around edges that are prone to synthesis artifacts are emphasized in the metric score. Two versions of morphological multiscale metric have been explored: (a) Morphological Pyramid Peak Signal-to-Noise Ratio metric (MP-PSNR) based on morphological pyramid decomposition, and (b) Morphological Wavelet Peak Signal-to-Noise Ratio metric (MW-PSNR) based on morphological wavelet decomposition. The performances of the proposed metrics have been tested using two databases which contain DIBR-synthesized images: the IRCCyN/IVC DIBR image database and MCL-3D stereoscopic image database. Proposed metrics achieve significantly higher correlation with human judgment compared to the state-of-the-art image quality metrics and compared to the tested metric dedicated to synthesis-related artifacts. The proposed metrics are computationally efficient given that the morphological operators involve only integer numbers and simple computations like min, max, and sum as well as simple calculation of MSE. MP-PSNR has slightly better performances than MW-PSNR. It has very good agreement with human judgment, Pearson's 0.894, Spearman 0.77 when it is tested on the MCL-3D stereoscopic image database. We have demonstrated that PSNR has particularly good agreement with human judgment when it is calculated between images at higher scales of morphological multi-scale representations. Consequently, simplified and in essence reduced versions of multi-scale metrics are proposed, taking into account only detailed images at higher decomposition scales. The reduced version of MP-PSNR has very good agreement with human judgment, Pearson's 0.904, Spearman 0.863 using IRCCyN/IVC DIBR image database. [ABSTRACT FROM AUTHOR]

Specular BRDF rendering traditionally approximates surface microstructure using a smooth normal distribution, but this ignores glinty effects, easily observable in the real world. While modeling the actual surface microstructure is possible, the resulting rendering problem is prohibitively expensive. Recently, Yan et al. [2014] and Jakob et al. [2014] made progress on this problem, but their approaches are still expensive and lack full generality in their material and illumination support. We introduce an efficient and general method that can be easily integrated in a standard rendering system. We treat a specular surface as a four-dimensional position-normal distribution, and fit this distribution using millions of 4D Gaussians, which we call elements. This leads to closed-form solutions to the required BRDF evaluation and sampling queries, enabling the first practical solution to rendering specular microstructure. [ABSTRACT FROM AUTHOR]

We propose an efficient technique for rendering visually plausible real-time soft shadows in screen space. First, we propose a novel blocker estimation technique based on a separable filter. Second, our technique performs a separable Gaussian blur in screen space over the hard shadows produced by the standard shadow mapping technique. Although blurring the hard shadows with a separable filter was done before in the literature using bilateral filtering, we use an alternative approach that minimizes artifacts. Since separated calculation is not possible for all cases, we provide data reutilization criteria based on two user-defined error thresholds called $$\alpha $$ and $$\beta $$ . As a consequence of using separable approaches for both stages of the light visibility estimation, our technique is able to improve rendering performance, especially when high-resolution shadow maps and filtering kernels are used. [ABSTRACT FROM AUTHOR]

Maps are widely used to visualize geo-information so that map users can develop related understandings about the real world. Such a process for communicating information is largely dependent on the rendering of map elements using different symbols (points and linear and area symbols). To meet the demand of more dynamic and comprehensive visualization in map rendering, it is essential to improve the rendering efficiency. This paper focuses on these research topics, especially the difficulty in constructing and drawing linear map symbols. By employing shader language, a function-based linear symbol building and rendering method is presented in this paper. The basic idea of this function-based method is to build a map-rendering solution that employs graphic processing unit (GPU) acceleration technology to improve the rendering efficiency. A ‘function’ is used to represent the algorithm that draws certain simple or complex linear map symbols. This function reflects the structure of a linear map symbol (describing the symbol construction information) and also the rendering process of the symbolized linear map elements (handled on a per-pixel basis by the shader program). Based on the Open Geospatial Consortium (OGC), Styled Layer Descriptor (SLD) specifications, four basic line types (i.e., solid lines, dashed lines, gradient color lines, and transition lines) are implemented in the proposed method, and the implementation of line markers, line joins and line caps is also discussed. Three experiments are conducted to demonstrate improvements in map rendering. The results show that a variety of linear map symbols can be constructed in a uniform way, which suggests that the proposed method addresses the difficulty in drawing linear map symbols. With this method, the efficiency of rendering linear map elements is substantially improved compared to using the graphics device interface plus (GDI+) and anti-grain geometry (AGG) methods; it also provides an applicable approach for developing map rendering systems. Using this function-based concept, the complexity of building linear map symbols and drawing linear map elements can be decreased. [ABSTRACT FROM AUTHOR]

A round-view autostereoscopic display is proposed based on an adaptive subpixel pre-rendering (ASPR) tracking algorithm. In the ASPR-based round-view system, 3D scene is rotated adaptively in a floating viewing zone by changing parallax image array (PIA) in real-time corresponding to the viewer's position. To verify and evaluate the achievements, an ASPR-based round-view autostereoscopic display prototype is developed. The results in both quality and quantity show that a round-view 3D perception is achieved in 90° ortho-stereoscopy viewing angle without pseud-3D effect, viewing zone flipping, and time delay. [ABSTRACT FROM AUTHOR]

Terrain visualization is an important aspect of many applications, especially of 3D geographic information systems, which try to preserve the accuracy of the applied terrain model. A discrepancy of data representation, efficient streaming and the application to a chosen mathematical model of the whole planet, still imposes a challenge to a number of large terrain rendering engines. In this paper, we present ellipsoidal clipmaps – a new way to apply geometry clipmaps to an ellipsoid. The ellipsoid is divided into three partitions, seamlessly stitched together. Unlike previous geometry clipmap approaches, based on preloaded grid upon which the terrain is elevated, the underlying ellipsoidal grid is generated on the fly in the vertex shader. The proposed method guarantees sub-pixel precision of the planet Earth reference ellipsoid surface calculation, exploiting GPU single precision floating-point arithmetic. A tight coupling with the implementation of clipmaps enables consistent caching and fast data streaming, while the usage of equidistant cylindrical projection for the source data minimizes preprocessing and preserves low-to-moderate texture distortion. [ABSTRACT FROM AUTHOR]

Bidirectional path tracing is known to perform poorly for the rendering of highly occluded scenes. Indeed, the connection strategy between light and eye subpaths does not take into account the visibility factor, presenting no contribution for many sampled paths. To improve the efficiency of bidirectional path tracing, we propose a new method for adaptive resampling of connections between light and eye subpaths. Aiming for this objective, we build discrete probability distributions of light subpaths based on a skeleton of the empty space of the scene. In order to demonstrate the efficiency of our algorithm, we compare our method to both standard bidirectional path tracing and a recent important caching method. [ABSTRACT FROM AUTHOR]

In recent year, 3DTV displays have become more popular in the consumer market. However, the visual discomfort is still the common problem when audiences view the stereoscopic 3D video for a long time period. Most of the discomfort comes from the excessive or improper disparity. To ease this problem, the comfortable disparity modification for existing depth-image-based rendering (DIBR) system is proposed in this paper. The proposed method contains several main parts such as degree-dependent algorithm, disparity range determination, and zero-parallax region based disparity remapping. To achieve customized 3D perception, a novel 3D adjustment mechanism is also proposed. Experimental results reveal that the proposed method can adjust the disparity effectively, which will be a great help for existing DIBR systems to generate comfortable 3D videos. [ABSTRACT FROM AUTHOR]

In this paper, a first hardware design for the 2D-compatible format and an architecture for the depth-image-based rendering (DIBR) is proposed. Compared to the format that uses one view plus one depth, the advanced 2D-compatible format reduces the bitrates of both color and depth frames. In order to achieve 3D image generation in real time, a hardware architecture of 2D-compatible format is firstly designed in this paper. In this paper, an edge-based DIBR algorithm is also proposed and implemented in to hardware architecture. The proposed edge-based DIBR algorithm achieves better image quality than the original DIBR algorithm. This paper combines these two architecture in to the advanced video and depth depacking architecture which can reduce the bitrates and increase the image quality of 3D video. Simulation results also show that image quality of the proposed system is better than that of the original DIBR algorithm. For the hardware cost, the proposed system requires 6.34k gates. The operation frequency can reach 100 MHz, which can supports the maximum frame size up to FHD (1920 x 1088) in real time. [ABSTRACT FROM AUTHOR]

A new stereoscopic image quality assessment database rendered using the 2D-image- plus-depth source, called MCL-3D, is described and the performance benchmarking of several known 2D and 3D image quality metrics using the MCL-3D database is presented in this work. Nine image-plus-depth sources are first selected, and a depth image-based rendering (DIBR) technique is used to render stereoscopic image pairs. Distortions applied to either the texture image or the depth image before stereoscopic image rendering include: Gaussian blur, additive white noise, down-sampling blur, JPEG and JPEG-2000 (JP2K) compression and transmission error. Furthermore, the distortion caused by imperfect rendering is also examined. The MCL-3D database contains 693 stereoscopic image pairs, where one third of them are of resolution 1024*768 and two thirds are of resolution 1920*1080. The pair-wise comparison was adopted in the subjective test for user friendliness, and the Mean Opinion Score (MOS) were computed accordingly. Finally, we evaluate the performance of several 2D and 3D image quality metrics applied to MCL-3D. All texture images, depth images, rendered image pairs in MCL-3D and their MOS values obtained in the subjective test are available to the public (http: //mcl.usc.edu/mcl-3d-database/) for future research and development. [ABSTRACT FROM AUTHOR]

We propose a novel approach to synthesizing images that are effective for training object detectors. Starting from a small set of real images, our algorithm estimates the rendering parameters required to synthesize similar images given a coarse 3D model of the target object. These parameters can then be reused to generate an unlimited number of training images of the object of interest in arbitrary 3D poses, which can then be used to increase classification performances.A key insight of our approach is that the synthetically generated images should be similar to real images, not in terms of image quality, but rather in terms of features used during the detector training. We show in the context of drone, plane, and car detection that using such synthetically generated images yields significantly better performances than simply perturbing real images or even synthesizing images in such way that they look very realistic, as is often done when only limited amounts of training data are available. [ABSTRACT FROM AUTHOR]

We propose a new adaptive rendering algorithm that enhances the performance of Monte Carlo ray tracing by reducing the noise, i.e., variance, while preserving a variety of high-frequency edges in rendered images through a novel prediction based reconstruction. To achieve our goal, we iteratively build multiple, but sparse linear models. Each linear model has its prediction window, where the linear model predicts the unknown ground truth image that can be generated with an infinite number of samples. Our method recursively estimates prediction errors introduced by linear predictions performed with different prediction windows, and selects an optimal prediction window minimizing the error for each linear model. Since each linear model predicts multiple pixels within its optimal prediction interval, we can construct our linear models only at a sparse set of pixels in the image screen. Predicting multiple pixels with a single linear model poses technical challenges, related to deriving error analysis for regions rather than pixels, and has not been addressed in the field. We address these technical challenges, and our method with robust error analysis leads to a drastically reduced reconstruction time even with higher rendering quality, compared to state-of-the-art adaptive methods. We have demonstrated that our method outperforms previous methods numerically and visually with high performance ray tracing kernels such as OptiX and Embree. [ABSTRACT FROM AUTHOR]