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International symposium on Symbolic and Numeric Algorithms for Scientific Computing (SYNASC)

作者： Sebastian-Aurelian Stefaniga Mihail Gaianu Computer Science Department UVT Timisoara Romania

ISBN: (纸本)9781538626276

As far as the problem of processing real time images studies showed that there can be two ways of analyze. On one hand is about the central processing unit (CPU) and the other is about the graphics processing unit (GPU). To obtain the highest possible performance they have to be used at the same time. Comparing the two processes, the result is that in the CPU, assignments as sequential operations and input-output are involved, in contrast to the GPU which is used for processes that can be made at the same time. Transposing these concepts of the real-time processing in medical digital images can be proved that the processing of an image is a response aproved within a certain time. The time we are speaking about lasts a few seconds or more less and images can be evaluated in a real-time medical side. Real-time image processing has become a very important objective and studied on the strength of its use in innovative media production, video calls, mobile phone cameras and video communication. The main purpose of this work is to improve the researching of a real-time digital image processing system applied on medical images. In this paper we try to present a method which is going to expose healthy and malignant tissues. Even if the physicians decisions remain the common method of detecting nonpalpable cancer, the method proposed in this paper plan to generate the fastest, easiest, and more accurate route, than in the case with classical techniques, by means of medical procedures. Our method of digital image processing by real-time processing is performed in order to allow medical specialists in radiology to detect abnormal tissues or cells, and then determine if a tumor is a malign or benign. The research illustrated in this paper involves an application toolbox with different filters, including segmentation, as well as various new tools for morphological filtering. More specifically, this paper focuses on CUDA as its parallel programming platform.

关键词： graphics processing units Central processing Unit Biomedical imaging Real-time systems Random access memory image processing Instruction sets

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[POSTER] Background image Registration as a Post-processing Technique in Diminished Reality Rendering Procedures

[POSTER] Background Image Registration as a Post-Processing ...

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IEEE International symposium on Mixed and Augmented Reality Workshops (ISMARW)

作者： Shohei Mori Jianing Qie Sei Ikeda Fumihisa Shibata Asako Kimura Hideyuki Tamura Keio University Ritsumeikan University

ISBN: (纸本)9781538614549

Diminished reality (DR) is a technique to remove undesirable objects from a video stream in real time. DR methods calculate a user's camera pose using vision- or sensor-based approaches to recover and overlay a background image to the camera view. Relying on 6DoF camera registration methods, DR results are often ruined due to misregistration. To solve this problem, we propose a registration framework as a post-processing technique in diminished reality rendering procedures to reduce the misalignment in an image space. We also reproduce motion blur to improve the image space alignment in the post-processing. The results showed remarkable improvement compared to sensor-based DR results. We argue that this postprocessing-based approach can be applied to almost all existing DR methods to improve their quality.

关键词： Cameras Rendering (computer graphics) Sensors Tracking Streaming media image sensors Pose estimation

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Crawl through Neighbors: A Simple Curve Reconstruction Algorithm

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computer graphics FORUM 2016年第5期35卷 177-186页

作者： Parakkat, Amal Dev Muthuganapathy, Ramanathan Indian Inst Technol Dept Engn Design Adv Geometr Comp Lab Madras 600036 Tamil Nadu India

Given a planar point set sampled from an object boundary, the process of approximating the original shape is called curve reconstruction. In this paper, a novel non-parametric curve reconstruction algorithm based on Delaunay triangulation has been proposed and it has been theoretically proved that the proposed method reconstructs the original curve under epsilon-sampling. Starting from an initial Delaunay seed edge, the algorithm proceeds by finding an appropriate neighbouring point and adding an edge between them. Experimental results show that the proposed algorithm is capable of reconstructing curves with different features like sharp corners, outliers, multiple objects, objects with holes, etc. The proposed method also works for open curves. Based on a study by a few users, the paper also discusses an application of the proposed algorithm for reconstructing hand drawn skip stroke sketches, which will be useful in various sketch based interfaces.

关键词： Categories and Subject Descriptors (according to ACM CCS) I 3 3 [computer graphics]: Picture image GenerationLine and curve generation

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Common Carotid Artery Lumen Segmentation from Cardiac Cycle-Resolved Cine Fast Spin Echo Magnetic Resonance Imaging

Common Carotid Artery Lumen Segmentation from Cardiac Cycle-...

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brazilian symposium on computer graphics and image processing (SIBGRAPI)

作者： Lıvia Rodrigues Roberto Medeiros De Souza Letícia Rittner Richard Frayne Roberto De Alencar Lotufo Faculty of Electrical and Computer Engineering Medical Image Computing Lab University of Campinas Campinas SP Brazil Department of Radiology and Clinical Neuroscience Hotchkiss Brain Institute University of Calgary Calgary AB Canada

Atherosclerosis is a disease responsible for millions of deaths each year, primarily due to heart attack and stroke. Magnetic resonance (MR) imaging is a non-invasive method that can be used to analyze the carotid artery and detect signs of atherosclerosis. Most MR methods acquire high contrast, static images. These methods, however, are sensitive to artifacts from cardiac motion, produce time-averaged images, and do not allow for carotid distensibility analysis. Carotid distensibility is an important, systematic measure of vascular health. Cine fast spin echo (FSE) is a new MR imaging that can obtain dynamic MR data (i.e., cardiac phase-resolved datasets). Dynamic imaging, however, comes at the cost of lower spatial resolution and signal-to-noise ratio, making these data potentially more difficult to segment. This paper introduces a semi-automated segmentation method that segments the common carotid artery (CCA) lumen across the cardiac cycle from dynamic MR images. To the best of our knowledge, this work is the first proposed technique for segmenting cardiac cycle-resolved cine FSE images. It combines a priori knowledge about the size and shape of the CCA, with the max-tree data structure, the tie-zone watershed transform (using identified internal and external markers) and supervised classification, to segment the carotid artery wall-lumen boundary. The user has to select only a seed point (centred in the carotid artery lumen). Technique performance was assessed using forty-five cine FSE data sets, each consisting of images reconstructed at sixteen temporal bins across the cardiac cycle. The automatic segmentation results were compared against the consensus of three different manual segmentation results. Our technique achieved an average Dice coefficient, sensitivity and false positive rate of 0.928±0.031 (mean ± standard deviation), 0.915 ± 0.037 and 0.056 ± 0.049, respectively. Our method achieved higher agreement versus the consensus of the three manual segmen

关键词： image segmentation Carotid arteries Imaging Transforms Atherosclerosis Histograms Shape

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Topology-aware image Compositing using NVLink 6

Topology-aware Image Compositing using NVLink

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6th IEEE symposium on Large Data Analysis and Visualization (LDAV)

作者： Christensen, Cameron Fogal, Thomas Luehr, Nathan Woolley, Cliff Univ Utah SCI Inst Salt Lake City UT 84112 USA NVIDIA Santa Clara CA USA

ISBN: (纸本)9781509056590

Compositing is a significant factor in distributed visualization performance at scale on high-performance computing (HPC) systems. For applications such as Para VieworVisIt, the common approach is “sort-last” rendering. For this approach, data are split up to be rendered such that each MPI rank has one or more portions of the over-all domain. After rendering its individual piece(s), each rank has one or more partial images that must be composited with the others to form the final image. The common approach for this step is to use a tree-like communication pattern to reduce the rendered images down to a single image to be displayed to the user. A variety of algorithms have been explored to perform this step efficiently in order to achieve interactive rendering on massive systems [7, 3, 8, 4].

关键词： graphics processing units Libraries Rendering (computer graphics) Data visualization computer architecture Bandwidth Topology Data visualisation computer Architecture COMPOSITE imageS Rendering Bandwidth topology Libraries graphics processing Unit High Performance Computing images

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Bayesian Collaborative Denoising for Monte Carlo Rendering

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computer graphics FORUM 2017年第4期36卷 137-153页

作者： Boughida, Malik Boubekeur, Tamy Paris Saclay Univ LTCI Telecom ParisTech Paris France

The stochastic nature of Monte Carlo rendering algorithms inherently produces noisy images. Essentially, three approaches have been developed to solve this issue: improving the ray-tracing strategies to reduce pixel variance, providing adaptive sampling by increasing the number of rays in regions needing so, and filtering the noisy image as a post-process. Although the algorithms from the latter category introduce bias, they remain highly attractive as they quickly improve the visual quality of the images, are compatible with all sorts of rendering effects, have a low computational cost and, for some of them, avoid deep modifications of the rendering engine. In this paper, we build upon recent advances in both non-local and collaborative filtering methods to propose a new efficient denoising operator for Monte Carlo rendering. Starting from the local statistics which emanate from the pixels sample distribution, we enrich the image with local covariance measures and introduce a nonlocal bayesian filter which is specifically designed to address the noise stemming from Monte Carlo rendering. The resulting algorithm only requires the rendering engine to provide for each pixel a histogram and a covariance matrix of its color samples. Compared to state-of-the-art sample-based methods, we obtain improved denoising results, especially in dark areas, with a large increase in speed and more robustness with respect to the main parameter of the algorithm. We provide a detailed mathematical exposition of our bayesian approach, discuss extensions to multiscale execution, adaptive sampling and animated scenes, and experimentally validate it on a collection of scenes.

关键词： CCS Concepts •Computing methodologies → Ray tracing image processing

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Multiple Axis-Aligned Filters for Rendering of Combined Distribution Effects

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computer graphics FORUM 2017年第4期36卷 155-166页

作者： Wu, Lifan Yan, Ling-Qi Kuznetsov, Alexandr Ramamoorthi, Ravi Univ Calif San Diego San Diego CA 92103 USA Univ Calif Berkeley Berkeley CA 94720 USA

Distribution effects such as diffuse global illumination, soft shadows and depth of field, are most accurately rendered using Monte Carlo ray or path tracing. However, physically accurate algorithms can take hours to converge to a noise-free image. A recent body of work has begun to bridge this gap, showing that both individual and multiple effects can be achieved accurately and efficiently. These methods use sparse sampling, GPU raytracers, and adaptive filtering for reconstruction. They are based on a Fourier analysis, which models distribution effects as a wedge in the frequency domain. The wedge can be approximated as a single large axis-aligned filter, which is fast but retains a large area outside the wedge, and therefore requires a higher sampling rate;or a tighter sheared filter, which is slow to compute. The state-of-the-art fast sheared filtering method combines low sampling rate and efficient filtering, but has been demonstrated for individual distribution effects only, and is limited by high-dimensional data storage and processing. We present a novel filter for efficient rendering of combined effects, involving soft shadows and depth of field, with global (diffuse indirect) illumination. We approximate the wedge spectrum with multiple axis-aligned filters, marrying the speed of axis-aligned filtering with an even more accurate (compact and tighter) representation than sheared filtering. We demonstrate rendering of single effects at comparable sampling and frame-rates to fast sheared filtering. Our main practical contribution is in rendering multiple distribution effects, which have not even been demonstrated accurately with sheared filtering. For this case, we present an average speedup of 6x compared with previous axis-aligned filtering methods.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.7 [computer graphics]: Three-Dimensional graphics and Realism—Color, shading, shadowing, and texture

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Space-Efficient Pointwise Computation of the Distance Transform on GPUs

Space-Efficient Pointwise Computation of the Distance Transf...

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IEEE International symposium on Parallel and Distributed processing Workshops and Phd Forum (IPDPSW)

作者： Numair Khan Mohamed Zahran Computer Science Department Brown University Providence Rhode Island Computer Science Department New York University New York New York

To minimize the amount of computation, traditional approaches to calculating the distance transform (DT) on a discrete volume propagate distance values in a local neighborhood. This results in recursive dependencies across the volume, requiring the DT to be calculated for all points in the domain en mass and stored as static values in memory. On the other hand, the ability to calculate the distance transform point-wise not only offers the prospect of efficient memory usage and scalability, but also a high degree of flexibility in accommodating the unique requirements of new application domains. However, among the current DT algorithms, the computationally intensive brute-force algorithm is the only one that allows point-wise computation. We demonstrate that the by decomposing it into a map and a reduction pattern on the massively parallel architecture of a modern graphics processing Unit (GPU), the brute-force distance transform algorithm achieves the threefold goals of memory efficiency, flexibility, and performance. We discuss a memory constrained implementation in the CUDA parallel programming model. The flexibility of point-wise computation at runtime is demonstrated by presenting an approximate and an anisotropic variant of the standard distance transform algorithm, and using these variants for the rendering of a CT scan image. Our approach allows the distance transform to be calculated for 1024 query points and up to 16 million feature points in 141.25 milliseconds while allowing direct control over the memory working-set size. These results demonstrate the potential of pointwise computation of the DT at runtime and the need for future algorithms to incorporate this capability.

关键词： Transforms graphics processing units Approximation algorithms Memory management Runtime Parallel processing Measurement

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Identifying Style of 3D Shapes using Deep Metric Learning

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computer graphics FORUM 2016年第5期35卷 207-215页

作者： Lim, Isaak Gehre, Anne Kobbelt, Leif Rhein Westfal TH Aachen Visual Comp Inst Aachen Germany

We present a method that expands on previous work in learning human perceived style similarity across objects with different structures and functionalities. Unlike previous approaches that tackle this problem with the help of hand-crafted geometric descriptors, we make use of recent advances in metric learning with neural networks (deep metric learning). This allows us to train the similarity metric on a shape collection directly, since any low- or high-level features needed to discriminate between different styles are identified by the neural network automatically. Furthermore, we avoid the issue of finding and comparing sub-elements of the shapes. We represent the shapes as rendered images and show how image tuples can be selected, generated and used efficiently for deep metric learning. We also tackle the problem of training our neural networks on relatively small datasets and show that we achieve style classification accuracy competitive with the state of the art. Finally, to reduce annotation effort we propose a method to incorporate heterogeneous data sources by adding annotated photos found online in order to expand or supplant parts of our training data.

关键词： Categories and Subject Descriptors (according to ACM CCS) I 3 5 [computer graphics]: Computational Geometry and Object Modeling style similarity deep metric learning

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A Study of Scientific Visualization on Heterogeneous Processors Using Legion 6

A Study of Scientific Visualization on Heterogeneous Process...

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6th IEEE symposium on Large Data Analysis and Visualization (LDAV)

作者： Yu, Lina Yu, Hongfeng Univ Nebraska Lincoln NE 68503 USA

ISBN: (纸本)9781509056590

We present a study of scientific visualization on heterogeneous processors using the Legion runtime system. We describe the main functions in our approach to conduct scientific visualization that can consist of multiple operations with different data requirements. Our approach can help users simplify programming on the data partition, data organization and data movement for distributed-memory heterogeneous architectures, thereby facilitating a simultaneous execution of multiple operations on modern and future supercomputers. We demonstrate the scalable performance and the easy usage of our approach by a hybrid data partitioning and distribution scheme for different data types using both CPUs and GPUs on a heterogeneous system.

关键词： Rendering (computer graphics) Data visualization graphics processing units Indexes Runtime image resolution Data visualisation Runtime image resolution graphics processing Unit data types MULTIPLE HEAD OPERATIONS PROCESSOR central processing units

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