Livro publicado em 2011, o autor Claudio Roberto da Silva trata sobre a riqueza e a grandeza do A... more Livro publicado em 2011, o autor Claudio Roberto da Silva trata sobre a riqueza e a grandeza do Amor de Deus que é e foi capaz de chegar ao extremo por amor de nossas almas. Baseado na espiritualidade e os ensinamentos católicos!
We advocate the use of point sets to represent shapes. We provide a definition of a smooth manifo... more We advocate the use of point sets to represent shapes. We provide a definition of a smooth manifold surface from a set of points close to the original surface. The definition is based on local maps from differential geometry, which are approximated by the method of moving least squares (MLS). We present tools to increase or decrease the density of the points, thus, allowing an adjustment of the spacing among the points to control the fidelity of the representation.
In this chapter, we present a high performance multi-scale 3D image processing framework to explo... more In this chapter, we present a high performance multi-scale 3D image processing framework to exploit the parallel processing power of multiple graphic processing units (Multi-GPUs) for medical image analysis. We developed GPU algorithms and data structures that can be applied to a wide range of 3D image processing applications and efficiently exploit the computational power and massive bandwidth offered by modern GPUs. Our framework helps scientists solve computationally intensive problems which previously required super computing power. To demonstrate the effectiveness of our framework and to compare to existing techniques, we focus our discussions on atlas construction -the application of understanding the development of the brain and the progression of brain diseases.
2008 IEEE International Conference on Shape Modeling and Applications, 2008
We address the problem of bandwidth selection in MLS surfaces. While the problem has received rel... more We address the problem of bandwidth selection in MLS surfaces. While the problem has received relatively little attention in the literature, we show that appropriate selection plays a critical role in the quality of reconstructed surfaces. We formulate the MLS polynomial fitting step as a kernel regression problem for both noiseless and noisy data. Based on this framework, we develop fast algorithms to find optimal bandwidths for a large class of weight functions. We show experimental comparisons of our method, which outperforms heuristically chosen functions and weights previously proposed. We conclude with a discussion of the implications of the Levin's two-step MLS projection for bandwidth selection.
ACM SIGGRAPH 2006 Sketches on - SIGGRAPH '06, 2006
: A sequence of progressive volume rendering steps for the SF1 dataset consisting of about 14 mil... more : A sequence of progressive volume rendering steps for the SF1 dataset consisting of about 14 million tetrahedra.
We introduce a robust moving least-squares technique for reconstructing a piecewise smooth surfac... more We introduce a robust moving least-squares technique for reconstructing a piecewise smooth surface from a potentially noisy point cloud. We use techniques from robust statistics to guide the creation of the neighborhoods used by the moving least squares (MLS) computation. This leads to a conceptually simple approach that provides a unified framework for not only dealing with noise, but also for enabling the modeling of surfaces with sharp features.
: A summary graph (middle) constructed from four graphs of molecules; colors indicate which input... more : A summary graph (middle) constructed from four graphs of molecules; colors indicate which input graphs contain a given feature with gray indicating the feature is common to all graphs.
2011 IEEE Symposium on Large Data Analysis and Visualization, 2011
Greetings and welcome to HotCloud '09, the first USENIX Workshop on Hot Topics in Cloud Computing... more Greetings and welcome to HotCloud '09, the first USENIX Workshop on Hot Topics in Cloud Computing! Our goal is to make HotCloud the premier forum for stimulating discussions on cloud computing research; we have attempted to keep its scope broad to encourage participation from both academia and industry. We are very pleased with the community response to this first edition of the workshop. HotCloud '09 has an exciting technical program which includes papers in the areas of platforms and architectures, resource management, storage cloud, virtual appliances, cloud applications, and pricing.
ACM SIGGRAPH 2006 Sketches on - SIGGRAPH '06, 2006
: (a) Wireframe model rendered using our real-time algorithm entirely on a GPU (GeForce 7800 GTX)... more : (a) Wireframe model rendered using our real-time algorithm entirely on a GPU (GeForce 7800 GTX) at 15.2 fps. Image resolution: 800 × 600. Shadow map resolution: 1024 2 . Num. samples per pixel: 88. (b) Opaque model rendered using the same technique at 15.8 fps.
We review the cell projection method of volume rendering, discussing back-to-front cell sorting, ... more We review the cell projection method of volume rendering, discussing back-to-front cell sorting, and approximations involved in hardware color computation and interpolation. We describe how the method accommodates cells with non-planar faces using view dependent subdivision into tetrahedra.
2008 IEEE Fourth International Conference on eScience, 2008
Provenance is essential in scientific experiments. It contains information that is key to preserv... more Provenance is essential in scientific experiments. It contains information that is key to preserving the data and to determine it's quality and authorship. In complex experiments and analyses, where multiple tools are used to derive data products, provenance captured by these tools must be combined in order to determine the complete lineage of the derived products. We propose a mediator-based architecture to integrate provenance information from multiple sources, which contains two key components: a global mediated schema that is general and capable of representing provenance information represented in different models; and an expressive query interface that supports complex queries over provenance information spread over multiple different sources. We also present a case study where we show how this model was applied to integrate provenance from three provenance-enabled systems.
: Our system is composed of many linked views. Structural MRI data is presented in a 3D visualiza... more : Our system is composed of many linked views. Structural MRI data is presented in a 3D visualization (top left) whose transfer function is manipulated using 2D widgets (bottom right). Users may select individual EEG sensors (yellow sphere) in the 3D visualization to explore its raw signal (bottom left) and time-frequency representation (middle right). The user also interacts with the time-frequency query area (top right) to generate spectral queries. The time-frequency display and query area are colormapped using an interactive widget (middle left). Combined with the settings in the parameter dialog, the query is issued and relevant sensors are colored blue according to their correlation with the query.
We propose a fast algorithm for rendering general irregular grids. Our method uses a sweep-plane ... more We propose a fast algorithm for rendering general irregular grids. Our method uses a sweep-plane approach to accelerate ray casting, and can handle disconnected and nonconvex (even with holes) unstructured irregular grids with a rendering cost that decreases as the "disconnectedness" decreases. The algorithm is carefully tailored to exploit spatial coherence even if the image resolution differs substantially from the object space resolution.
IEEE Transactions on Visualization and Computer Graphics, 2005
Harvesting the power of modern graphics hardware to solve the complex problem of real-time render... more Harvesting the power of modern graphics hardware to solve the complex problem of real-time rendering of large unstructured meshes is a major research goal in the volume visualization community. While, for regular grids, texture-based techniques are well-suited for current GPUs, the steps necessary for rendering unstructured meshes are not so easily mapped to current hardware. We propose a novel volume rendering technique that simplifies the CPU-based processing and shifts much of the sorting burden to the GPU, where it can be performed more efficiently. Our hardware-assisted visibility sorting algorithm is a hybrid technique that operates in both object-space and image-space. In object-space, the algorithm performs a partial sort of the 3D primitives in preparation for rasterization. The goal of the partial sort is to create a list of primitives that generate fragments in nearly sorted order. In image-space, the fragment stream is incrementally sorted using a fixed-depth sorting network. In our algorithm, the object-space work is performed by the CPU and the fragment-level sorting is done completely on the GPU. A prototype implementation of the algorithm demonstrates that the fragment-level sorting achieves rendering rates of between one and six million tetrahedral cells per second on an ATI Radeon 9800.
The first Provenance Challenge was set up in order to provide a forum for the community to unders... more The first Provenance Challenge was set up in order to provide a forum for the community to understand the capabilities of different provenance systems and the expressiveness of their provenance representations. To this end, a Functional Magnetic Resonance Imaging workflow was defined, which participants had to either simulate or run in order to produce some provenance representation, from which a set of identified queries had to be implemented and executed. Sixteen teams responded to the challenge, and submitted their inputs. In this paper, we present the challenge workflow and queries, and summarise the participants contributions.
IEEE Transactions on Visualization and Computer Graphics, 2007
While there have been advances in visualization systems, particularly in multi-view visualization... more While there have been advances in visualization systems, particularly in multi-view visualizations and visual exploration, the process of building visualizations remains a major bottleneck in data exploration. We show that provenance metadata collected during the creation of pipelines can be reused to suggest similar content in related visualizations and guide semi-automated changes. We introduce the idea of query-by-example in the context of an ensemble of visualizations, and the use of analogies as first-class operations in a system to guide scalable interactions. We describe an implementation of these techniques in VisTrails, a publiclyavailable, open-source system.
Computational Geometry: Theory and Applications, 1999
We present a method for compressing non-manifold polygonal meshes, i.e., polygonal meshes with si... more We present a method for compressing non-manifold polygonal meshes, i.e., polygonal meshes with singularities, which occur very frequently in the real-world. Most efficient polygonal compression methods currently available are restricted to a manifold mesh: they require converting a non-manifold mesh to a manifold mesh, and fail to retrieve the original model connectivity after decompression.The present method works by converting the original model to a manifold model, encoding the manifold model using an existing mesh compression technique, and clustering, or stitching together during the decompression process vertices that were duplicated earlier to faithfully recover the original connectivity. This paper focuses on efficiently encoding and decoding the stitching information. Using a naive method, the stitching information would incur a prohibitive cost, while our methods guarantee a worst case cost of bits per vertex replication, where m is the number of non-manifold vertices. Furthermore, when exploiting the adjacency between vertex replications, many replications can be encoded with an insignificant cost.By interleaving the connectivity, stitching information, geometry and properties, we can avoid encoding repeated vertices (and properties bound to vertices) multiple times; thus a reduction of the size of the bit-stream of about 10% is obtained compared with encoding the model as a manifold.
Livro publicado em 2011, o autor Claudio Roberto da Silva trata sobre a riqueza e a grandeza do A... more Livro publicado em 2011, o autor Claudio Roberto da Silva trata sobre a riqueza e a grandeza do Amor de Deus que é e foi capaz de chegar ao extremo por amor de nossas almas. Baseado na espiritualidade e os ensinamentos católicos!
We advocate the use of point sets to represent shapes. We provide a definition of a smooth manifo... more We advocate the use of point sets to represent shapes. We provide a definition of a smooth manifold surface from a set of points close to the original surface. The definition is based on local maps from differential geometry, which are approximated by the method of moving least squares (MLS). We present tools to increase or decrease the density of the points, thus, allowing an adjustment of the spacing among the points to control the fidelity of the representation.
In this chapter, we present a high performance multi-scale 3D image processing framework to explo... more In this chapter, we present a high performance multi-scale 3D image processing framework to exploit the parallel processing power of multiple graphic processing units (Multi-GPUs) for medical image analysis. We developed GPU algorithms and data structures that can be applied to a wide range of 3D image processing applications and efficiently exploit the computational power and massive bandwidth offered by modern GPUs. Our framework helps scientists solve computationally intensive problems which previously required super computing power. To demonstrate the effectiveness of our framework and to compare to existing techniques, we focus our discussions on atlas construction -the application of understanding the development of the brain and the progression of brain diseases.
2008 IEEE International Conference on Shape Modeling and Applications, 2008
We address the problem of bandwidth selection in MLS surfaces. While the problem has received rel... more We address the problem of bandwidth selection in MLS surfaces. While the problem has received relatively little attention in the literature, we show that appropriate selection plays a critical role in the quality of reconstructed surfaces. We formulate the MLS polynomial fitting step as a kernel regression problem for both noiseless and noisy data. Based on this framework, we develop fast algorithms to find optimal bandwidths for a large class of weight functions. We show experimental comparisons of our method, which outperforms heuristically chosen functions and weights previously proposed. We conclude with a discussion of the implications of the Levin's two-step MLS projection for bandwidth selection.
ACM SIGGRAPH 2006 Sketches on - SIGGRAPH '06, 2006
: A sequence of progressive volume rendering steps for the SF1 dataset consisting of about 14 mil... more : A sequence of progressive volume rendering steps for the SF1 dataset consisting of about 14 million tetrahedra.
We introduce a robust moving least-squares technique for reconstructing a piecewise smooth surfac... more We introduce a robust moving least-squares technique for reconstructing a piecewise smooth surface from a potentially noisy point cloud. We use techniques from robust statistics to guide the creation of the neighborhoods used by the moving least squares (MLS) computation. This leads to a conceptually simple approach that provides a unified framework for not only dealing with noise, but also for enabling the modeling of surfaces with sharp features.
: A summary graph (middle) constructed from four graphs of molecules; colors indicate which input... more : A summary graph (middle) constructed from four graphs of molecules; colors indicate which input graphs contain a given feature with gray indicating the feature is common to all graphs.
2011 IEEE Symposium on Large Data Analysis and Visualization, 2011
Greetings and welcome to HotCloud '09, the first USENIX Workshop on Hot Topics in Cloud Computing... more Greetings and welcome to HotCloud '09, the first USENIX Workshop on Hot Topics in Cloud Computing! Our goal is to make HotCloud the premier forum for stimulating discussions on cloud computing research; we have attempted to keep its scope broad to encourage participation from both academia and industry. We are very pleased with the community response to this first edition of the workshop. HotCloud '09 has an exciting technical program which includes papers in the areas of platforms and architectures, resource management, storage cloud, virtual appliances, cloud applications, and pricing.
ACM SIGGRAPH 2006 Sketches on - SIGGRAPH '06, 2006
: (a) Wireframe model rendered using our real-time algorithm entirely on a GPU (GeForce 7800 GTX)... more : (a) Wireframe model rendered using our real-time algorithm entirely on a GPU (GeForce 7800 GTX) at 15.2 fps. Image resolution: 800 × 600. Shadow map resolution: 1024 2 . Num. samples per pixel: 88. (b) Opaque model rendered using the same technique at 15.8 fps.
We review the cell projection method of volume rendering, discussing back-to-front cell sorting, ... more We review the cell projection method of volume rendering, discussing back-to-front cell sorting, and approximations involved in hardware color computation and interpolation. We describe how the method accommodates cells with non-planar faces using view dependent subdivision into tetrahedra.
2008 IEEE Fourth International Conference on eScience, 2008
Provenance is essential in scientific experiments. It contains information that is key to preserv... more Provenance is essential in scientific experiments. It contains information that is key to preserving the data and to determine it's quality and authorship. In complex experiments and analyses, where multiple tools are used to derive data products, provenance captured by these tools must be combined in order to determine the complete lineage of the derived products. We propose a mediator-based architecture to integrate provenance information from multiple sources, which contains two key components: a global mediated schema that is general and capable of representing provenance information represented in different models; and an expressive query interface that supports complex queries over provenance information spread over multiple different sources. We also present a case study where we show how this model was applied to integrate provenance from three provenance-enabled systems.
: Our system is composed of many linked views. Structural MRI data is presented in a 3D visualiza... more : Our system is composed of many linked views. Structural MRI data is presented in a 3D visualization (top left) whose transfer function is manipulated using 2D widgets (bottom right). Users may select individual EEG sensors (yellow sphere) in the 3D visualization to explore its raw signal (bottom left) and time-frequency representation (middle right). The user also interacts with the time-frequency query area (top right) to generate spectral queries. The time-frequency display and query area are colormapped using an interactive widget (middle left). Combined with the settings in the parameter dialog, the query is issued and relevant sensors are colored blue according to their correlation with the query.
We propose a fast algorithm for rendering general irregular grids. Our method uses a sweep-plane ... more We propose a fast algorithm for rendering general irregular grids. Our method uses a sweep-plane approach to accelerate ray casting, and can handle disconnected and nonconvex (even with holes) unstructured irregular grids with a rendering cost that decreases as the "disconnectedness" decreases. The algorithm is carefully tailored to exploit spatial coherence even if the image resolution differs substantially from the object space resolution.
IEEE Transactions on Visualization and Computer Graphics, 2005
Harvesting the power of modern graphics hardware to solve the complex problem of real-time render... more Harvesting the power of modern graphics hardware to solve the complex problem of real-time rendering of large unstructured meshes is a major research goal in the volume visualization community. While, for regular grids, texture-based techniques are well-suited for current GPUs, the steps necessary for rendering unstructured meshes are not so easily mapped to current hardware. We propose a novel volume rendering technique that simplifies the CPU-based processing and shifts much of the sorting burden to the GPU, where it can be performed more efficiently. Our hardware-assisted visibility sorting algorithm is a hybrid technique that operates in both object-space and image-space. In object-space, the algorithm performs a partial sort of the 3D primitives in preparation for rasterization. The goal of the partial sort is to create a list of primitives that generate fragments in nearly sorted order. In image-space, the fragment stream is incrementally sorted using a fixed-depth sorting network. In our algorithm, the object-space work is performed by the CPU and the fragment-level sorting is done completely on the GPU. A prototype implementation of the algorithm demonstrates that the fragment-level sorting achieves rendering rates of between one and six million tetrahedral cells per second on an ATI Radeon 9800.
The first Provenance Challenge was set up in order to provide a forum for the community to unders... more The first Provenance Challenge was set up in order to provide a forum for the community to understand the capabilities of different provenance systems and the expressiveness of their provenance representations. To this end, a Functional Magnetic Resonance Imaging workflow was defined, which participants had to either simulate or run in order to produce some provenance representation, from which a set of identified queries had to be implemented and executed. Sixteen teams responded to the challenge, and submitted their inputs. In this paper, we present the challenge workflow and queries, and summarise the participants contributions.
IEEE Transactions on Visualization and Computer Graphics, 2007
While there have been advances in visualization systems, particularly in multi-view visualization... more While there have been advances in visualization systems, particularly in multi-view visualizations and visual exploration, the process of building visualizations remains a major bottleneck in data exploration. We show that provenance metadata collected during the creation of pipelines can be reused to suggest similar content in related visualizations and guide semi-automated changes. We introduce the idea of query-by-example in the context of an ensemble of visualizations, and the use of analogies as first-class operations in a system to guide scalable interactions. We describe an implementation of these techniques in VisTrails, a publiclyavailable, open-source system.
Computational Geometry: Theory and Applications, 1999
We present a method for compressing non-manifold polygonal meshes, i.e., polygonal meshes with si... more We present a method for compressing non-manifold polygonal meshes, i.e., polygonal meshes with singularities, which occur very frequently in the real-world. Most efficient polygonal compression methods currently available are restricted to a manifold mesh: they require converting a non-manifold mesh to a manifold mesh, and fail to retrieve the original model connectivity after decompression.The present method works by converting the original model to a manifold model, encoding the manifold model using an existing mesh compression technique, and clustering, or stitching together during the decompression process vertices that were duplicated earlier to faithfully recover the original connectivity. This paper focuses on efficiently encoding and decoding the stitching information. Using a naive method, the stitching information would incur a prohibitive cost, while our methods guarantee a worst case cost of bits per vertex replication, where m is the number of non-manifold vertices. Furthermore, when exploiting the adjacency between vertex replications, many replications can be encoded with an insignificant cost.By interleaving the connectivity, stitching information, geometry and properties, we can avoid encoding repeated vertices (and properties bound to vertices) multiple times; thus a reduction of the size of the bit-stream of about 10% is obtained compared with encoding the model as a manifold.
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Papers by Claudio Silva