Background In actual surgery, smoke and bleeding due to cauterization processes provide important visual cues to the surgeon, which have been proposed as factors in surgical skill assessment. While several virtual rea...
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Background In actual surgery, smoke and bleeding due to cauterization processes provide important visual cues to the surgeon, which have been proposed as factors in surgical skill assessment. While several virtual reality (VR)-based surgical simulators have incorporated the effects of bleeding and smoke generation, they are not realistic due to the requirement of real-time performance. To be interactive, visual update must be performed at at least 30 Hz and haptic (touch) information must be refreshed at 1 kHz. Simulation of smoke and bleeding is, therefore, either ignored or simulated using highly simplified techniques, since other computationally intensive processes compete for the available Central Processing Unit (CPU) resources. Methods In this study we developed a novel low-cost method to generate realistic bleeding and smoke in VR-based surgical simulators, which outsources the computations to the graphical processing unit (GPU), thus freeing up the CPU for other time-critical tasks. This method is independent of the complexity of the organ models in the virtual environment. User studies were performed using 20 subjects to determine the visual quality of the simulations compared to real surgical videos. Results The smoke and bleeding simulation were implemented as part of a laparoscopic adjustable gastric banding (LAGB) simulator. For the bleeding simulation, the original implementation using the shader did not incur noticeable overhead. However, for smoke generation, an input/output (I/O) bottleneck was observed and two different methods were developed to overcome this limitation. Based on our benchmark results, a buffered approach performed better than a pipelined approach and could support up to 15 video streams in real time. Human subject studies showed that the visual realism of the simulations were as good as in real surgery (median rating of 4 on a 5-point Likert scale). Conclusions Based on the performance results and subject study, both bleeding and
Previous research has shown multihue scales to be well-suited to code categorical features and shown lightness scales to be well-suited to code ordinal quanti. ties. We introduce an algorithm, Motley, that produces co...
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Previous research has shown multihue scales to be well-suited to code categorical features and shown lightness scales to be well-suited to code ordinal quanti. ties. We introduce an algorithm, Motley, that produces color scales varying in both hue and lightness, intended to be effective for both categorical and ordinal coding, allowing users to determine both absolute and relative quantities efficiently and accurately. The algorithm first determines the lightnesses of scale colors to maximize perceived lightness differences and establish the lightness ordering, generating separate search spaces for each scale position. It then selects hues by heuristic search to maximize the discriminability of the scale. It produces scales that are ordered with respect to lightness but unordered with respect to hue and thus more discriminable than typical multihue lightness scales. In an experimental evaluation on human subjects, Motley's scales enabled accurate judgments of relative quantity, with response times superior to unordered multihue scales and comparable to ordered lightness scales, and enabled accuracy and speed of judgments of absolute quantity superior to lightness scales and comparable to multihue scales. (dagger)Published 2009 Wiley Periodicals, Inc. Col Res Appl, 35, 18-28, 2010;Published online 17 November 2009 in Wiley InterScience (***). DOI 10.1002/col.20559
Methods: This new GPU implementation has been designed from the ground-up to use the graphics card's strengths and to avoid its weaknesses. The CS GPU algorithm takes into account beam hardening, off-axis softenin...
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Methods: This new GPU implementation has been designed from the ground-up to use the graphics card's strengths and to avoid its weaknesses. The CS GPU algorithm takes into account beam hardening, off-axis softening, kernel tilting, and relies heavily on raytracing through patient imaging data. Implementation details are reported as well as a multi-GPU solution. Results: An overall single-GPU acceleration factor of 908x was achieved when compared to a nonoptimized version of the CS algorithm implemented in PlanUNC in single threaded central processing unit (CPU) mode, resulting in approximatively 2.8 s per beam for a 3D dose computation on a 0.4 cm grid. A comparison to an established commercial system leads to an acceleration factor of approximately 29x or 0.58 versus 16.6 s per beam in single threaded mode. An acceleration factor of 46x has been obtained for the total energy released per mass (TERMA) calculation and a 943x acceleration factor for the CS calculation compared to PlanUNC. Dose distributions also have been obtained for a simple water-lung phantom to verify that the implementation gives accurate results. Conclusions: These results suggest that GPUs are an attractive solution for radiation therapy applications and that careful design, taking the GPU architecture into account, is critical in obtaining significant acceleration factors. These results potentially can have a significant impact on complex dose delivery techniques requiring intensive dose calculations such as intensity-modulated radiation therapy (IMRT) and arc therapy. They also are relevant for adaptive radiation therapy where dose results must be obtained rapidly.
Improving performance in sports requires a better understanding of the perception-action loop employed by athletes. Because of its inherent limitations, video playback doesn't permit this type of in-depth analysis...
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Improving performance in sports requires a better understanding of the perception-action loop employed by athletes. Because of its inherent limitations, video playback doesn't permit this type of in-depth analysis. Interactive, immersive virtual reality can overcome these limitations and foster a better understanding of sports performance.
Many multimedia collections include only metadata such as date created and file size and remain largely unannotated. So, browsing them is cumbersome. Automatic content-analysis techniques yield metadata in the form of...
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Many multimedia collections include only metadata such as date created and file size and remain largely unannotated. So, browsing them is cumbersome. Automatic content-analysis techniques yield metadata in the form of high-level content-based descriptors. However, these techniques' accuracy is insufficient to automate collection categorization. A human is essential to validate and organize automated techniques' results. MediaTable helps users efficiently categorize an image or video collection. A tabular interface gives an overview of multimedia items and associated metadata, and a bucket list lets users quickly categorize materials. MediaTable uses familiar interface techniques for sorting, filtering, selection, and visualization. Evaluations with expert and nonexpert users indicate that MediaTable supports efficient categorization and provides valuable insight into the collection.
We present a novel representation and rendering method for free-viewpoint video of human characters based on multiple input video streams. The basic idea is to approximate the articulated 3D shape of the human body us...
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We present a novel representation and rendering method for free-viewpoint video of human characters based on multiple input video streams. The basic idea is to approximate the articulated 3D shape of the human body using a subdivision into textured billboards along the skeleton structure. Billboards are clustered to fans such that each skeleton bone contains one billboard per source camera. We call this representation articulated billboards. In the paper we describe a semi-automatic, data-driven algorithm to construct and render this representation, which robustly handles even challenging acquisition scenarios characterized by sparse camera positioning, inaccurate camera calibration, low video resolution, or occlusions in the scene. First, for each input view, a 2D pose estimation based on image silhouettes, motion capture data, and temporal video coherence is used to create a segmentation mask for each body part. Then, from the 2D poses and the segmentation, the actual articulated billboard model is constructed by a 3D joint optimization and compensation for camera calibration errors. The rendering method includes a novel way of blending the textural contributions of each billboard and features an adaptive seam correction to eliminate visible discontinuities between adjacent billboards textures. Our articulated billboards do not only minimize ghosting artifacts known from conventional billboard rendering, but also alleviate restrictions to the setup and sensitivities to errors of more complex 3D representations and multi-view reconstruction techniques. Our results demonstrate the flexibility and the robustness of our approach with high quality free-viewpoint video generated from broadcast footage of challenging, uncontrolled environments.
The AniViz tool for making visualization animations is based on two principles. First, it's desirable to directly turn the results of data exploration and visualization into animation content. Second, users can cr...
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The AniViz tool for making visualization animations is based on two principles. First, it's desirable to directly turn the results of data exploration and visualization into animation content. Second, users can create a complex animation sequence by blending several simple effects. AniViz provides a set of motion templates; users create desirable effects as instances of those templates. It also provides a set of operators to edit an instance or combine multiple instances into a sequence of effects. Users can fine-tune parameters associated with an instance or a sequence in a keyframe style. Users can specify the length of each segment in the animation, or AniViz can automatically allocate the length on the basis of a distance metric. AniViz offers these functionalities through a simple, easy-to-use interface. The Web extra is a video that shows the author's animation tool, AniViz. [ABSTRACT FROM PUBLISHER]
This paper explains the development of a highly efficient progressive 3-D mesh geometry coder based on the region adaptive transform in the spectral mesh compression method. A hierarchical set partitioning technique, ...
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This paper explains the development of a highly efficient progressive 3-D mesh geometry coder based on the region adaptive transform in the spectral mesh compression method. A hierarchical set partitioning technique, originally proposed for the efficient compression of wavelet transform coefficients in high-performance wavelet-based image coding methods, is proposed for the efficient compression of the coefficients of this transform. Experiments confirm that the proposed coder employing such a region adaptive transform has a high compression performance rarely achieved by other state of the art 3-D mesh geometry compression algorithms. A new, high-performance fixed spectral basis method is also proposed for reducing the computational complexity of the transform. Many-to-one mappings are employed to relate the coded irregular mesh region to a regular mesh whose basis is used. To prevent loss of compression performance due to the low-pass nature of such mappings, transitions are made from transform-based coding to spatial coding on a per region basis at high coding rates. Experimental results show the performance advantage of the newly proposed fixed spectral basis method over the original fixed spectral basis method in the literature that employs one-to-one mappings.
A perspective image represents the spatial relationships of objects in a scene as they appear from a single viewpoint. In contrast, a multi-perspective image combines what is seen from several viewpoints into a single...
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A perspective image represents the spatial relationships of objects in a scene as they appear from a single viewpoint. In contrast, a multi-perspective image combines what is seen from several viewpoints into a single image. Despite their incongruity of view, effective multi-perspective images are able to preserve spatial coherence and can depict, within a single context, details of a scene that are simultaneously inaccessible from a single view, yet easily interpretable by a viewer. In computer vision, multi-perspective images have been used for analysing structure revealed via motion and generating panoramic images with a wide field-of-view using mirrors. In this STAR, we provide a practical guide on topics in multi-perspective modelling and rendering methods and multi-perspective imaging systems. We start with a brief review of multi-perspective image techniques frequently employed by artists such as the visual paradoxes of Escher, the Cubism of Picasso and Braque and multi-perspective panoramas in cel animations. We then characterize existing multi-perspective camera models, with an emphasis on their underlying geometry and image properties. We demonstrate how to use these camera models for creating specific multi-perspective rendering effects. Furthermore, we show that many of these cameras satisfy the multi-perspective stereo constraints and we demonstrate several multi-perspective imaging systems for extracting 3D geometry for computer vision. The participants learn about topics in multi-perspective modelling and rendering for generating compelling pictures for computer graphics and in multi-perspective imaging for extracting 3D geometry for computer vision. We hope to provide enough fundamentals to satisfy the technical specialist without intimidating curious digital artists interested in multi-perspective images. The intended audience includes digital artists, photographers and computer graphics and computer vision researchers using or building multi-perspe
Urban spaces consist of a complex collection of buildings, parcels, blocks and neighbourhoods interconnected by streets. Accurately modelling both the appearance and the behaviour of dense urban spaces is a significan...
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Urban spaces consist of a complex collection of buildings, parcels, blocks and neighbourhoods interconnected by streets. Accurately modelling both the appearance and the behaviour of dense urban spaces is a significant challenge. The recent surge in urban data and its availability via the Internet has fomented a significant amount of research in computer graphics and in a number of applications in urban planning, emergency management and visualization. In this paper, we seek to provide an overview of methods spanning computer graphics and related fields involved in this goal. Our paper reports the most prominent methods in urban modelling and rendering, urban visualization and urban simulation models. A reader will be well versed in the key problems and current solution methods.
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