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11th Pacific conference on Computer Graphics and Applications

作者： Granier, X Goesele, M Heidrich, W Seidel, HP Univ British Columbia Vancouver BC V5Z 1M9 Canada

ISBN: (纸本)0769520286

Interactive visualization of complex, real-world light sources has so far not been feasible. In this paper, we present an hardware accelerated direct lighting algorithm based on a recent high quality light source acquisition technique. By introducing an approximate reconstruction of the exact model, a multi-pass rendering approach, and a compact data representation, we are able to achieve interactive frame rates. The method is part of the processing pipeline from light source acquisition to high quality lighting of a virtual world.

关键词： local illumination light source modeling hardware rendering image-based rendering physically-based modeling and acquisition

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Multiplication-free architecture for daubechies wavelet transforms using algebraic integers

Multiplication-free architecture for daubechies wavelet tran...

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conference on Advanced Signal Processing Algorithms Architectures and Implementations XIII

作者： Wahid, K Dimitrov, v Jullien, G Univ Calgary Dept ECE ATIPS Lab Calgary AB Canada

ISBN: (纸本)0819450782

The 2-Dimensional Wavelet Transform has been proven to be a highly effective tool for image analysis and used in JPEG2000 standard. There are many publications which demonstrate that using wavelet transform in time and space, combined with a multiresolution approach, leads to an efficient and effective method of compression. In particular, the four and six coefficient Daubechies filters have excellent spatial and spectral locality, properties which make them useful in image compression. In this paper, we propose a multiplication-free and parallel vLSI architecture for Daubechies wavelets where the computations are free from round-off errors until the final reconstruction step. In our algorithm, error-free calculations are achieved by the use of Algebraic Integer encoding of the wavelet coefficients. Compared to other DWT algorithms such as: embedded zero-tree, recursive or semi-recursive and conventional fixed-point binary architecture, our technique has lower hardware cost, lower computational power and optimized data-bus utilization.

关键词： 2-D wavelet transforms algebraic integers daubechies wavelets image and video compression

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3D reconstruction of the human spine from bi-planar radiographs:: Using multi-scale wavelets analysis and splines interpolators for semi-automation

3D reconstruction of the human spine from bi-planar radiogra...

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Medical Imaging 2003 conference

作者： Deschênes, S Godbout, B Branchaud, D Mitton, D Pomero, v Bleau, A Skalli, W de Guise, J ETS CRCHUM Lab Rech Imagerie & Orthoped Montreal PQ H2L 4M1 Canada

ISBN: (纸本)0819448338

We propose a new fast stereoradiographic 3D reconstruction method for the spine. User input is limited to few points passing through the spine on two radiographs and two line segments representing the end plates of the limiting vertebrae. A 3D spline that hints the positions of the vertebrae in space is then generated We then use wavelet multi-scale analysis (WMSA) to automatically localize specific features in both lateral and frontal radiographs. The WMSA gives an elegant spectral investigation that leads to gradient generation and edge extraction. Analysis of the information contained at several scales leads to the detection of 1) two curves enclosing the vertebral bodies' walls and 2) inter-vertebral spaces along the spine. from this data, we extract four points per vertebra per view, corresponding to the corners of the vertebral bodies. These points delimit a hexahedron in space where we can match the vertebral body. This hexahedron is then passed through a 3D statistical database built using local and global information generated from a bank of normal and scohotic spines. Finally, models of the vertebrae are positioned with respect to these landmarks, completing the 3D reconstruction.

关键词： medical imaging 3D reconstruction bi-planar radiographs wavelets multi-scale spline spine vertebra model matching

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A position sensitive detector for SPIDR - a mission to map the cosmic web

A position sensitive detector for SPIDR - a mission to map t...

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6th International conference on Position Sensitive Detectors

作者： Lapington, JS Chakrabarti, S Cook, T Gsell, JC Gsell, vT Boston Univ Ctr Space Phys Boston MA 02215 USA

The primary goal of the Spectroscopy and Photometry of the IGM's Diffuse Radiation (SPIDR) mission is to detect and map the huge filamentary structures, the "cosmic web", predicted to be present in the IGM. To accomplish this task the SPIDR instrument comprises six imaging spectrographs providing high-resolution spatial maps of IGM features in the critical OvI and CIv lines at both rest and red-shifted wavelengths. Each spectrograph uses a two-dimensional position sensitive microchannel plate detector to image Uv dispersed by a normal incidence grating, encoding spectral and spatial information. Two-dimensional imaging is recovered by tomographic reconstruction of data from the slowly spinning spacecraft. The detector configuration utilizes an open faced microchannel plate stack coated with a Uv photocathode. The conservative imaging requirements are met by a wedge and strip anode whose performance has been enhanced by using the image charge technique. image charge provides a highly stable and predictable detector response which has enabled us to use software simulation to improve the linearity of the readout considerably. (C) 2003 Published by Elsevier B.v.

关键词： multi-spectral Uv spectrograph microchannel plate WSA detector image charge

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A position sensitive detector for SPIDR - a mission to map the cosmic web

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NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 2003年第1-2期513卷 159-162页

作者： Lapington, JS Chakrabarti, S Cook, T Gsell, JC Gsell, vT Boston Univ Ctr Space Phys Boston MA 02215 USA

关键词： multi-spectral Uv spectrograph microchannel plate WSA detector image charge

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Anisotropic diffusion of surface normals for feature preserving surface reconstruction

Anisotropic diffusion of surface normals for feature preserv...

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International conference on 3D Imaging, Modeling, Processing, visualization and Transmission (3DIMPvT)

作者： T. Tasdizen R. Whitaker School of Computing University of Utah USA

For 3D surface reconstruction problems with noisy and incomplete range data measured from complex scenes with arbitrary topologies, a low-level representation, such as level set surfaces, is used. Such surface reconstruction is typically accomplished by minimizing a weighted sum of datamodel discrepancy and model smoothness terms. We introduce a new nonlinear model smoothness term for surface reconstruction based on variations of the surface normals. A direct solution requires solving a fourth-order partial differential equation (PDE), which is very difficult with; conventional numerical techniques. Our solution is based on processing the normals separately from the surface, which allows us to separate the problem into two second-order PDEs. The proposed method can smooth complex, noisy surfaces, while preserving sharp, geometric features, and it is a natural generalization of edge-preserving methods in image processing, such as anisotropic diffusion.

关键词： Surface reconstruction Anisotropic magnetoresistance image reconstruction Layout Noise measurement Topology Level set Shape Density measurement Multi-stage noise shaping

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reconstruction of 3-D objects from raster altimeter data

Reconstruction of 3-D objects from raster altimeter data

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International conference on CAD Systems in Microelectronics (CADSM)

作者： A. Melnyk v. Emets I. Moroz v. Marchyvka INTRON Limited L'viv Ukraine INTRON Ltd. Lviv UKRAINE

In this paper we give a general scheme for investigation of the problem of analytical description of 3D objects using raster altimeter data. During the last few years, interest in 3D data describing of urban areas has increased. This data is needed for a variety of applications such as town planning, architecture, microclimate investigations or transmitter placement for telecommunication. Our investigations are concerned with the feasibility of building extraction using laser data, obtained by airborne laser scanners, as input data.

关键词： Algorithm design and analysis image reconstruction Buildings Pixel Urban areas Cities and towns Transmitters data mining Object detection Phase detection

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Conditional entropy maximization for PET

Conditional entropy maximization for PET

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IEEE International conference on Systems, Man and Cybernetics

作者： P.P. Mondal K. Rajan Department of Physics Indian Institute of Science Bangalore India

Maximum Likelihood (ML) estimation is extensively used for estimating emission densities from clumped and incomplete measurement data in Positron Emission Tomography (PET) modality. reconstruction produced by ML-algorithm has been found noisy because it does not make use of available prior knowledge. Bayesian estimation provides such a platform for the inclusion of prior knowledge in the reconstruction procedure. But modeling a prior distribution is a cumbersome task and needs a lot of insight. In this work, we have proposed a conditional entropy maximization algorithm for PET modality, which is a generalization of maximum likelihood algorithm. We have imposed self-normalization condition for the determination of prior distribution. It is found that as prior distribution tends to uniform distribution, the conditional entropy maximization algorithm reduces to maximum likelihood algorithm. Simulated experimental results have shown that images reconstructed using maximum entropy algorithm are qualitatively better than those generated by ML-algorithm.

关键词： Entropy Positron emission tomography Maximum likelihood estimation image reconstruction Bayesian methods Parameter estimation Physics Distribution functions Probability density function Density measurement

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3D vessel axis extraction using 2D calibrated x-ray projections for coronary modeling

3D vessel axis extraction using 2D calibrated x-ray projecti...

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Medical Imaging 2003 conference

作者： Young, S Movassaghi, B Weese, J Rasche, v Philips Res Labs D-22335 Hamburg Germany

ISBN: (纸本)0819448338

A new approach for 3D vessel centreline extraction using multiple, ECG-gated, calibrated X-ray angiographic projections of the coronary arteries is described. The proposed method performs direct extraction of 3D vessel centrelines, without the requirement to either first compute prior 2D centreline estimates, or perform a complete volume reconstruction. A front propagation-based algorithm, initialised with one or more 3D seed points, is used to explore a volume of interest centred on the projection geometry's isocentre. The expansion of a 3D region is controlled by forward projecting boundary points into all projection images to compute vessel response measurements, which are combined into a 3D propagation speed so that the front expands rapidly when all projection images yield high vessel responses. vessel centrelines are obtained by reconstructing the paths of fastest propagation. Based on these axes, a volume model of the coronaries can be constructed by forward projecting axis points into the 2D images where the borders axe detected. The accuracy of the method was demonstrated via a comparison of automatically extracted centrelines with 3D centrelines derived from manually segmented projection data.

关键词： 3D vessel centreline tracking 3D rotational angiography front propagation coronary arteries

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Combining intensity and range images for 3D modelling

Combining intensity and range images for 3D modelling

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IEEE International conference on image Processing

作者： P. Dias v. Sequeira F. vaz J.G.M. Goncalves IEETA University of Aveiro Portugal Joint Research Centre European Commission Italy

This paper presents a process combining range and intensity based techniques, in order to get better 3D models than those obtained using these techniques separately. The procedure needs an initial estimation for internal and external camera parameters for two or more intensity images. The technique uses passive triangulation to refine initial camera calibrations and ensure a good registration of range and video data sets. Afterwards, corresponding points from the intensity images are triangulated and introduced in the original range cloud of points. The objective is to complete the models in areas where data is missing or to increase the resolution in areas of high interest and 3D contents.

关键词： Cameras image edge detection Calibration Equations image reconstruction Spatial resolution Detectors Clouds Laser modes Position measurement

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