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A NOVEL ray-tracing TECHNIQUE FOR INDOOR RADIO SIGNAL PREDICTION

JOURNAL OF ELECTROMAGNETIC WAVES AND APPLICATIONS 2011年第8-9期25卷 1179-1190页

作者： Sarker, M. S. Reza, A. W. Dimyati, K. Univ Malaya Fac Engn Dept Elect Engn Kuala Lumpur 50603 Malaysia

The potential implementation of personal communication systems inside buildings requires a thorough understanding of signal propagation within buildings. As practical measurements are costly, difficult in accuracy, and time consuming that translate into costly service for the consumer, there is an increasing demand for efficient and accurate simulation-based indoor radio propagation prediction tools. Therefore, this study explores a new, efficient, and faster ray-tracing technique based on the Binary Angle Division algorithm for indoor radio signal prediction. The obtained simulated results are compared with other existing techniques to prove the superiority of the proposed algorithm in terms of both computational efficiency and accuracy. The results obtained from this study show satisfactory performance and good agreement with the simulated results.

关键词： RADIO wave propagation PERSONAL communication service systems MEASUREMENT SIMULATION methods & models ray tracing algorithms MATHEMATICAL proofs PERFORMANCE evaluation

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A ray tracing Approach to Diffusion Curves

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COMPUTER GRAPHICS FORUM 2011年第4期30卷 1345-1352页

作者： Bowers, John C. Leahey, Jonathan Wang, Rui Univ Massachusetts Amherst Amherst MA 01003 USA

Diffusion curves [OBW+ 08] provide a flexible tool to create smooth-shaded images from curves defined with colors. The resulting image is typically computed by solving a Poisson equation that diffuses the curve colors to the interior of the image. In this paper we present a new method for solving diffusion curves by using ray tracing. Our approach is analogous to final gathering in global illumination, where the curves define source radiance whose visible contribution will be integrated at a shading pixel to produce a color using stochastic ray tracing. Compared to previous work, the main benefit of our method is that it provides artists with extended flexibility in achieving desired image effects. Specifically, we introduce generalized curve colors called shaders that allow for the seamless integration of diffusion curves with classic 2D graphics including vector graphics (e.g. gradient fills) and raster graphics (e.g. patterns and textures). We also introduce several extended curve attributes to customize the contribution of each curve. In addition, our method allows any pixel in the image to be independently evaluated, without having to solve the entire image globally (as required by a Poisson-based approach). Finally, we present a GPU-based implementation that generates solution images at interactive rates, enabling dynamic curve editing. Results show that our method can easily produce a variety of desirable image effects.

关键词： DIFFUSION LIGHTING ray tracing algorithms COMPUTER-generated imagery COMPUTER graphics

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Numerical Method of the ray tracing-Node Analyzing Method for Solving 2-D Transient Coupled Heat Transfer in a Rectangular Semitransparent Medium

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NUMERICAL HEAT TRANSFER PART A-APPLICATIONS 2009年第5期55卷 465-486页

作者： Luo, Jian-Feng Shen, Xi Natl Univ Def Technol Coll Sci Dept Phys Changsha 410073 Hunan Peoples R China

For the ray tracing-node analyzing method for solving 2-D transient coupled heat transfer, the transient differential energy equation is discretized using the fully implicit finite-difference method and the radiative source term is expressed by the radiative transfer coefficients (RTCs). The Patankar linearization method is used to linearize the radiative source term and the opaque boundary conditions, and then the opaque boundary conditions are dealt with the additional source term method (ASTM). The ADI method is applied to solve the nominal linearizing equations. This study shows that using ASTM to handle the opaque boundary conditions is necessary;otherwise, the solution diverges.

关键词： ray tracing algorithms HEAT transfer RADIATIVE transfer HEAT -- Radiation & absorption LINEAR differential equations FINITE differences

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ReduceM: Interactive and memory efficient ray tracing of large models

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COMPUTER GRAPHICS FORUM 2008年第4期27卷 1313-1321页

作者： Lauterbach, Christian Yoon, Sung-eui Tang, Ming Manocha, Dinesh Univ N Carolina Chapel Hill NC 27515 USA Korea Adv Inst Sci & Technol Taejon South Korea Zhejiang Univ Hangzhou Peoples R China

We present a novel representation and algorithm, ReduceM, for memory efficient ray tracing of large scenes. ReduceM exploits the connectivity between triangles in a mesh and decomposes the model into triangle strips. We also describe a new stripification algorithm, Strip-RT, that can generate long strips with high spatial coherence. Our approach uses a two-level traversal algorithm for ray-primitive intersection. In practice, ReduceM can significantly reduce the storage overhead and ray trace massive models with hundreds of millions of triangles at interactive rates on desktop PCs with 4-8GB of main memory.

关键词： algorithms Computer algorithms ray tracing algorithms Computer graphics Geometrical optics Memory

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An Improved Method of Linear Travel-Time Interpolation ray tracing Algorithm

ACTA PHYSICA POLONICA A

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ACTA PHYSICA POLONICA A 2010年第4期118卷 521-526页

作者： Hao-Quan, W. North Univ China Key Lab Instrument Sci & Dynam Measurement Minist Educ Natl Key Lab Sci & Technol Elect Test & Measureme Taiyuan 030051 Shanxi Peoples R China

The linear travel-time interpolation algorithm is improved by the method of ray tracing based on finite difference scheme of eikonal equation. It can simulate the more complex medium. Using the algorithm to calculate travel-time and paths of tracing rays, it is more rapid and accurate than the other conventional methods. The linear travel-time interpolation ray tracing algorithm has a drawback: rays cannot go round the low velocity area if the launching point, the receiving point and the low velocity area distribute on the same column (row). Aiming at the drawback, an improved algorithm is proposed on the basis of researching reconstruction theories. The given algorithm adopts a cross-scanning strategy to carry out forward processing and uses discrete points as the secondary sources to simplify backward processing. The numerical simulation experiments show that the rays can go round the low velocity areas located in the same column (row) of the launching points and the receiving points. rays scan over the global region only once.

关键词： TRAVEL time (Traffic engineering) INTERPOLATION ray tracing algorithms EIKONAL equation FINITE differences

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Modelling diffraction during ray tracing using the concept of energy flow lines

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JOURNAL OF QUANTITATIVE SPECTROSCOPY & RADIATIVE TRANSFER 2008年第8期109卷 1374-1383页

作者： Hesse, E. Univ Hertfordshire Sci & Technol Res Inst Hatfield AL10 9AB Herts England

The ray-tracing with diffraction on facets (RTDF) model is suitable for rapid computation of scattering on faceted dielectric objects such as ice crystals. It combines ray tracing with diffraction on flat facets. The model calculates diffraction using an approximation for the far-field direction of the Poynting vector. In this paper, an estimate based on an approximation by Prosser for the electric and magnetic fields describing diffraction at a slit is used to calculate energy flow lines and their far-field deflection angles. Best-fit formulas describing the dependence of the far-field deflection angle on the size parameter, angle of incidence and the position of the flow line in the plane of the slit are derived and incorporated into the RTDF model. Phase functions for hexagonal columns are presented and compared with an analytic technique, the separation of variables method, and geometric optics with projected area diffraction. (C) 2007 Elsevier Ltd. All rights reserved.

关键词： OPTICAL diffraction ray tracing algorithms ICE crystals OPTICS

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Development and verification of an MOC code employing assembly modular ray tracing and efficient acceleration techniques

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ANNALS OF NUCLEAR ENERGY 2009年第8期36卷 1013-1020页

作者： Tang, Chuntao Zhang, Shaohong Shanghai Jiao Tong Univ Sch Nucl Sci & Engn Shanghai 200240 Peoples R China

In this paper, we report the development and verification of a method of characteristics (MOC) code, PEACH, at Shanghai Jiao Tong University. Both the usual flat-source step characteristics (SC) scheme and the linear source (LS) approximation scheme are adopted for the tracking calculation along the neutron trajectory. The assembly-based modular ray tracing (AMRT) technique that possesses a good geometric flexibility and high efficiency is employed, which makes PEACH able to deal with practical LWR assembly and core problems. Moreover, in order to reduce the computational time of the MOC iteration process, both the multi/few-group two-level cell-based coarse mesh finite difference (CMFD) acceleration and the exponential function interpolation technique are used. This results in a significant acceleration. Numerical results for the OECD NEA C5G7 MOX benchmark problem and a 69-group BWR mini-core problem demonstrate that PEACH is accurate and efficient. Numerical results also demonstrate that the LS scheme is more efficient than the SC scheme, taking less time and system memory to generate results of comparable accuracy. In addition, we find that MOC with CMFD acceleration always converges with almost the same number of outer iterations regardless of the physical problem size and the discretization parameters used. This shows an ideal linear relationship between the run time and the geometric size of the problem. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： ray tracing algorithms CHARACTERISTIC functions CODING theory APPROXIMATION theory GEOMETRIC analysis ACCELERATION (Mechanics) ITERATIVE methods (Mathematics) FINITE differences EXPONENTIAL functions SHANGHAI Jiao Tong University (Shanghai, China)

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Spectral ray tracing in Problems of Photorealistic Imagery Construction

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PROGRAMMING AND COMPUTER SOFTWARE 2011年第5期37卷 236-244页

作者： Zhdanov, D. D. Potemin, I. S. Galaktionov, V. A. Barladyan, B. Kh. Vostryakov, K. A. Shapiro, L. Z. SI Vavilov State Opt Inst St Petersburg 199034 Russia Russian Acad Sci MV Keldysh Appl Math Inst Moscow 125047 Russia

This paper analyzes color rendering problems arising in computer imaging of scenes with complex optical properties. The sources of these errors for imagery constructed on the basis of the RGB space are analyzed and an efficient and correct algorithm is proposed for spectral imagery. These solutions are applied to problems of direct stochastic and inverse deterministic ray tracing. In addition, complex scenes with mixed optical properties defined in different (including RGB) models are proposed to be treated by an efficient and correct algorithm for reducing all optical properties into a single spectral model.

关键词： SPECTRAL energy distribution ray tracing algorithms LUMINANCE (Video) OPTICAL properties LIGHT sources DIGITAL images

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Model of Inhomogeneous building facade for ray tracing method

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ELECTRONICS LETTERS 2008年第23期44卷 1341-1342页

作者： Kwon, S. Koh, I-S. Moon, H-W. Lim, J-W. Yoon, Y. J. Yonsei Univ Dept Elect & Elect Engn Microwave & Antenna Lab Seoul 120749 South Korea Inha Univ Grad Sch Informat Technol & Telecommun Inchon South Korea Minist Informat & Commun Radio Res Lab Seoul 140848 South Korea

A model for considering the scattering effect of an inhomogeneous building facade as an effective reflection coefficient of a homogeneous surface in a ray tracing method is proposed. Hence, the computational complexity of a ray tracing method that considers the effect of inhomogeneous building facades can be preserved as in the conventional method.

关键词： Machine theory Scattering (Mathematics) Computational complexity Inhomogeneous materials ray tracing algorithms

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Full automatic preprocessing of digital map for 2.5D ray tracing propagation model in urban microcellular environment

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WAVES IN RANDOM AND COMPLEX MEDIA 2013年第3期23卷 267-278页

作者： Liu, Zhong-Yu Guo, Li-Xin Tao, Wei Xidian Univ Sch Sci Xian Peoples R China

Due to the importance of digital map to ray-tracing (RT) algorithm, intelligent preprocessing techniques for the geometric information of buildings are improved, taking into account the characteristic of quasi three-dimensional (2.5D) RT method. By using these techniques, the geometrical factors, which have little or no effect on the prediction results, are neglected from the digital map, and the reduction of the number of blocking test is achieved in the process of executing the RT routine. With the proposed preprocessing of the digital map in urban microcellular environments, the improvement in the computational efficiency is clearly demonstrated without sensibly affecting the accuracy of the propagation prediction.

关键词： DIGITAL mapping ray tracing algorithms MATHEMATICAL models GEOMETRIC analysis INFORMATION theory BLOCKING sets

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