Ray-tracing Acceleration Techniques Research Articles

Coupling radiative, conductive and convective heat-transfers in a single Monte Carlo algorithm: A general theoretical framework for linear situations.

It was recently shown that radiation, conduction and convection can be combined within a single Monte Carlo algorithm and that such an algorithm immediately benefits from state-of-the-art computer-graphics advances when dealing with complex geometries. The theoretical foundations that make this coupling possible are fully exposed for the first time, supporting the intuitive pictures of continuous thermal paths that run through the different physics at work. First, the theoretical frameworks of propagators and Green's functions are used to demonstrate that a coupled model involving different physical phenomena can be probabilized. Second, they are extended and made operational using the Feynman-Kac theory and stochastic processes. Finally, the theoretical framework is supported by a new proposal for an approximation of coupled Brownian trajectories compatible with the algorithmic design required by ray-tracing acceleration techniques in highly refined geometry.

Modified wavefront decomposition method for fast and accurate ray-tracing simulation

This study presents the modified wavefront decomposition method as a new ray-tracing acceleration technique for indoor propagation modelling. In this method, the exact propagation paths of the rays that reach the receiver after multiple reflections and/or refractions are calculated. Thus, the electromagnetic field at the receiver is obtained with a high accuracy. When only reflections are considered, our method simplifies to the multiple image theory or shooting and bouncing ray/image approach already available in the literature. However, the modified wavefront decomposition method calculates the exact propagation paths toward the receiver even if the rays encounter multiple refractions or a sequence of reflections and refractions. This novel contribution is specially important in indoor applications where through-the-wall propagation is usually noticeable. The significance of the proposed method is that the accuracy in the received field is obtained by shooting a few rays to the space around the transmitter. Consequently, a considerable reduction of the simulation time is achieved. The simulations show that the proposed method outperforms the traditional wavefront decomposition method. Furthermore, concurrent application of the proposed method and the previously published acceleration techniques is shown possible, which results in simulation time reduction of more than 11 times for a typical simulated indoor environment.

Accuracy and computational efficiency improvement of ray tracing using line search theory

This study presents a new ray tracing acceleration technique for site-specific propagation modelling in indoor environments. It overcomes one of the major problems regarding the computational efficiency of shooting-and-bouncing-ray (SBR) method, that is most of the rays emitted from the source do not reach the receiver whereas all of them must be traced. Our proposed method solves this problem in a two-step procedure based on the idea of line search theory. In the first step, called the bracketing phase, the solid angles around the transmitter that transport electromagnetic power to the receiver are determined. In the second step, called the sectioning or zoom phase, the accuracy is improved by iteratively increasing the tessellation frequency of the source in the power-transporting solid angles. No ray will be sent through non-power-transporting solid angles in the sectioning phase. Applying the method to a typical indoor problem is presented and the results are compared with fully 3-D SBR simulation. It is observed that power-transporting solid angles constitute only a small fraction of the total space around the source through which the rays are launched. Therefore a high gain in terms of computational efficiency (about 550–800% saving in the simulation time) is achieved.

Use of geometry in finite element thermal radiation combined with ray tracing

In heat transfer for space applications, the exchanges of energy by radiation play a significant role. In this paper, we present a method which combines the geometrical definition of the model with a finite element mesh. The geometrical representation is advantageous for the radiative component of the thermal problem while the finite element mesh is more adapted to the conductive part. Our method naturally combines these two representations of the model. The geometrical primitives are decomposed into cells. The finite element mesh is then projected onto these cells. This results in a ray tracing acceleration technique. Moreover, the ray tracing can be performed on the exact geometry, which is necessary if specular reflectors are present in the model. We explain how the geometrical method can be used with a finite element formulation in order to solve thermal situation including conduction and radiation. We illustrate the method with the model of a satellite.

Efficient Time-Domain Ray-Tracing Technique for the Analysis of Ultra-Wideband Indoor Environments including Lossy Materials and Multiple Effects

This paper presents an efficient application of the Time-Domain Uniform Theory of Diffraction (TD-UTD) for the analysis of Ultra-Wideband (UWB) mobile communications for indoor environments. The classical TD-UTD formulation is modified to include the contribution of lossy materials and multiple-ray interactions with the environment. The electromagnetic analysis is combined with a ray-tracing acceleration technique to treat realistic and complex environments. The validity of this method is tested with measurements performed inside the Polytechnic building of the University of Alcala and shows good performance of the model for the analysis of UWB propagation.

Theory and application of specular path perturbation

In this paper we apply perturbation methods to the problem of computing specular reflections in curved surfaces. The key idea is to generate families of closely related optical paths by expanding a given path into a high-dimensional Taylor series. Our path perturbation method is based on closed-form expressions for linear and higher-order approximations of ray paths, which are derived using Fermat's Variation Principle and the Implicit Function Theorem (IFT). The perturbation formula presented here holds for general multiple-bounce reflection paths and provides a mathematical foundation for exploiting path coherence in ray tracing acceleration techniques and incremental rendering. To illustrate its use, we describe an algorithm for fast approximation of specular reflections on curved surfaces; the resulting images are highly accurate and nearly indistinguishable from ray traced images.

Ray-tracing acceleration techniques

Site-specific software tools for propagation predictions in multipath environments for modern mobile radio communications require computationally efficient procedures. In this paper, an acceleration technique and its associated software package are described. They present a relevant execution time saving. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 25: 363–365, 2000.

Ray-tracing acceleration techniques

Ray-tracing acceleration techniques

Analyzing Parallel Ray Tracing Algorithms

The research on Photo-Realistic rendering intends to develop algorithms in order to render images of synthetic or artificial high quality models. One of the most popular methods that allows to obtain this kind of images is ray tracing. This technique requires the evaluation of a very large number of light contributions in a scene that could be defined by several hundred thousand objects. To this end, the ray tracing algorithm must calculate a large number of ray-object intersections, which makes this algorithm very expensive in computation time. Fortunately, ray tracing is an algorithm intrinsically parallel which offers several potential acceleration techniques to reduce such higher rendering time in generating one single image. This paper presents a survey of the parallel processing for the image synthesis by means of ray tracing. Firstly, we describe the ray tracing algorithm and the different sequential acceleration techniques briefly. This paper focuses on the different parallelization strategies of ray tracing. These strategies are presented from the point of view of their main differences, as well as their advantages and disadvantages. Afterward, we analyze the main interesting and promising research fields on the ray tracing acceleration technique, although these same fields can also help in other rendering algorithms.

Efficient ray-tracing acceleration techniques for radio propagation modeling

Ray-tracing and uniform theory of diffraction techniques are already widely applied to site-specific radio propagation modeling for wireless applications. Software tools using such techniques may take considerable computation time in the analysis of the propagation conditions in a given environment even for a short mobile terminal route. Efficient acceleration techniques are required to make such analysis tools practical for the design of modern radio systems. To reduce computation time, ray-tracing routines must be applied only to those areas where rays are likely to exist. This is achieved by using ray-path search algorithms prior to performing any actual ray tracing. An efficient ray-path search algorithm is presented. First, a two-dimensional version is described, which is valid for indoor and microcell studies. Then, an extension to the three-dimensional case is explained in detail. Finally, the software tool Radio Tracer using such techniques is briefly described, and some comparisons between experimental results and computed predictions for indoor and outdoor scenarios are shown.

Análisis de propagación inalámbrica usando una nueva técnica 3D de aceleración de trazado de rayos

El rápido crecimiento en las comunicaciones inalámbricas ha llevado a la necesidad de evaluar de un modo eficazla radiopropagación. Las densas áreas urbanas y los ambientes interiores tienden a ser entornos complejos querequieren una gran cantidad de obstáculos para ser modelados. En tales entornos, la radiopropagación de las ondases un fenómeno extremadamente complicado y las técnicas de trazado de rayos han sido ampliamente usadas paraanalizar estos problemas. Sin embargo, el principal problema del algoritmo de trazado de rayos es su lentitud. Por lotanto, el proceso del trazado de rayos se debe realizar con técnicas que mejoran la eficiencia de las simulaciones. Eneste artículo se presenta una nueva técnica de aceleración de trazado de rayos que combina las técnicas AZB y octreepara la subdivisión del espacio. Esta nueva técnica se validó mediante mediciones de propagación en dos ambienteshospitalarios, encontrando que el máximo error entre los valores medidos y calculados fue inferior al 8%. La nuevatécnica permitió reducir el tiempo de cálculo a la mitad comparado con la técnica AZB. Sin embargo, a medida quecrece el número de interacciones que se evalúan, crece el tiempo computacional.