Two Algorithms for Fast Polyhedron Ray-Tracing

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Discrete Ray-Tracing of Huge Voxel Spaces

The quality of images produced by Discrete Ray-Tracing voxel spaces is highly dependent on 3d grid resolution. The huge amount of memory needed to store such grids often discards discrete Ray-Tracing as a practical visualization algorithm. The use of an octree can drastically change this when most of space is empty, as such is the case in most scenes. Although the memory problem can be bypassed using the octree, the performance problem still remains. A known fact is that the performance of discrete traversal is optimal for quite low resolutions. This problem can be easily solved by dividing the task in two steps, working in two low resolutions instead of just one high resolution, thus taking advantage of optimal times in both steps. This is possible thanks to the octree property of representing the same scene in several different resolutions. This article presents a two step Discrete Ray-Tracing method using an octree and shows, by comparing it with the single step version, that a substantial gain in performance is achieved.     

基于中介面加快光线跟踪计算

提出一种新的光线跟踪方法,以提高光线找到相交面片的效率.它在场景中生成一些面积较大的规整中介面片,然后为中介面上的每个点建立一个场,以记录到达该点的不同方向的光线将相交的面片.由此,光线跟踪时,一条光线可方便地找到相交的中介面,并通过查找中介面上所记录的内容,就能得到它所相交的面片.与已有方法相比,新方法不仅能很好加速主光线与阴影光线的计算,而且能很好地加速反射、折射等二次光线的计算.它能在GPU上方便地实现,并能有效地处理动态场景.     

基于声线跟踪法开发超声无损检测动态仿真软件

以“声线跟踪法”为基础，运用面向对象的编程语言VisualC＋＋和三维场景开发工具OpenGL，按照面向对象的程序设计思想开发了超声波无损检测仿真软件。该系统实现了超声检测过程的三维可视化并对超声波传播路径和A型显示进行了较为准确的模拟。该文对仿真过程中的三维介质建模和传播路径模拟计算等关键问题进行了详细的讨论，采用CSG／B-Rep混合模型表示法对三维介质模型进行快速建模，并且采用声线跟踪法对传播路径进行较为准确的模拟。最后通过仿真实例，验证了算法的有效性。     

Accelerating ARTS

A major fraction of ray-tracing computation time is spent on ray-object intersection calculation. To reduce this calculation cost, one method, ARTS, subdivides the 3-D object space into voxels and uses a 3-D line-drawing routine to simulate ray propagation in the subdivided space to select objects for intersection testing. Finer space subdivision gives better object selection resolution and fewer ray-object tests. However, as the subdivision increases, the improvement is offset by a linear degradation of the line-drawing-routine efficiency and a cubic growth of the memory requirement. We solve these time and memory scalability problems in ARTS using an adaptive 3-D line-drawing algorithm, which traverses space with multiple stepsizes, and a hybrid database that employs both the octree and the 3-D array data structures. The space traversal cost in our solution grows logarithmically with the subdivision increase, and the memory requirement grows only linearly.     

Generating High Quality Pictures by Ray-Tracing

Ray-casting techniques provide a very general framework in which many problems can be solved in a much easier way than with conventional methods. This is particularly true for the illumination model when a high level of realism is required. Another interesting feature of ray-casting is its ability to display a wide class of algebraic surfaces with a minimum of approximation. Both aspects are developed in this paper where a full lighting model, based on a theoretical approach, is presented. Then, an algorithm for the display of surfaces of revolution is described.
Computation time is the major drawback of ray-tracing. Special purpose parallel processors seem to offer a good price/performance ratio compared to the use of supercomputers.     

偏振光线跟踪绘制技术研究进展综述

光线跟踪是计算机图形学中一种高真实感绘制方法,传统的绘制算法忽略了光的偏振效应.而研究表明:在光线跟踪中加入光的偏振效应,能对绘制结果产生重要的影响.偏振光线跟踪是预测绘制技术的研究核心,它不仅可以提供高真实感的绘制效果,而且已被应用于偏振场景仿真和导航等领域.目前,偏振光线跟踪在国内尚未有相关工作.在预测绘制的框架下,根据偏振光线跟踪的流程,对偏振光线跟踪绘制技术的要点与关键问题进行了分析、总结与展望.     

采用GPU的视觉定位系统加速实验

计算机视觉在实际应用中的主要瓶颈是系统的准确性和实时性,而实时性的提高又受限于计算机中处理器的处理速度。在一个视觉定位伺服实际系统中,要求有很高的实时性,尝试研究使用GPU建立实时的视觉系统的实际性。视觉定位系统软件分为图像粗定位(目标识别)、图像精定位、运动解算等几部分。当识别图像像素为640×480时,采用单独GPU加速的方式,比CPU加速了2.1444倍,采用CPU和GPU相结合的方式,比CPU加速了4.1548倍。     

一种光线跟踪的包容性检测算法

提出了一维投影判别法和基于右手定则的空间多边形的包容性检测算法,该算法将空间多边形和线面交点投影至一维坐标轴并进行包容性的必要性判定,以少量逻辑比较即可排除大多数无关面片,然后利用基于右手定则的包容性检测算法,进行充分性判定。理论计算和模型中的应用表明,此算法用时显著减少。     

基于光线追迹的方形微通道X光器件模拟

为研究方形微通道X光器件的成像特性,基于光线追迹法建立了一种方形微通道X光器件的数学模型。利用数值模拟的方法对比了方形微通道X光器件和传统多毛细管X光器件的传输效率,研究了方形微通道X光器件的潜在光源位置分辨能力、光斑形貌等成像特性。证实了方形微通道X光器件在深空探测和空间X射线成像领域的潜在应用价值。     

Interactive-Rate Animation Generation by Parallel Progressive Ray-Tracing on Distributed-Memory Machines

We describe a dynamic load-balancing algorithm for ray-tracing by progressive refinement on a distributed-memory parallel computer. Parallelization of progressive ray-tracing for single images is difficult because of the inherent sequential nature of the sample location generation process, which is optimized (and different) for any given image. Parallelization of progressive ray-tracing when generating image sequences at a fixed interactive rate is even more difficult, because of the time and synchronization constraints imposed on the system. The fixed frame rate requirement complicates matters and even renders meaningless traditional measures of parallel system performance (e.g., speedup). We show how to overcome these problems, which, to the best of our knowledge, have not been treated before. Exploiting the temporal coherence between frames enables us to both accelerate rendering and improve the load-balance throughout the sequence. Our dynamic load-balance algorithm combines local and global methods to account not only for rendering performance, but also for communication overhead and synchronization issues. The algorithm is shown to be robust to the harsh environment imposed by a time-critical application, such as the one we consider.     

城市微小区射线跟踪定位原理与模型

文章把无线电波射线跟踪技术引入定位技术中,提出了射线跟踪场强、时延、到达角定位序列的概念,从原理上说明了场强、时延、到达角定位序列的正确性和实用性,并用模型验证了场强、时延定位序列的唯一性,证明了序列定位原理与方法的正确性。     

Filtering, Clustering and Hierarchy Construction: a New Solution for Ray-Tracing Complex Scenes

Data structures that handle very complex scenes (hundreds of thousands of objects) have in the past either been laboriously built by hand, or have required the determination of unintuitive parameter values by the user. It is often the case that an incorrect choice of these parameters can result in greedy memory requirements or severely degraded performance. As a remedy to this problem we propose a new data structure which is fully automatic since it does not require the user to determine any input parameters. The structure is built by first filtering the input objects by size, subsequently applying a clustering step to objects of the same size and finally building a hierarchy of uniform grids . We then show that this data structure can be efficiently constructed. The implementation of the shows that the new structure is stable since it's memory requirements grow linearly with the size of the scene, and that it presents a satisfactory compromise between memory usage and computational efficiency. A detailed comparison with previous data structures is also presented in the results.     

基于光路追踪法的激光能量沉积并行计算

在激光驱动惯性约束聚变的数值模拟中,通常使用光路追踪法来计算激光能量沉积。为了适应大规模、高效率的数值模拟需要,本文提出了分组流水线的光路追踪并行策略,能够充分提高大量光线在区域分解网格下的并行性。     

Seismic Ray-Tracing and Earth Mesh Modeling on Various Parallel Architectures

A major research topic in geophysics deals with the modelization of the Earth interior, and seismic tomography is a means to improve knowledge in this field. In order to improve the accuracy of existing methods, huge quantities of information must be computed. We present in this paper the design of a software program implementing a fast seismic ray-tracing in an Earth mesh. We show that massively parallel computational resources may be used to process huge quantity of data. We present experimentations on several computational equipments with various hardware architectures (a parallel computer, a cluster, and a Grid) and report which parallel programming paradigm best suits each of these equipments.     

一种面向机动的低成本姿态测量系统

载体作机动运动时,基于加速度计和磁传感器的姿态测量系统易受载体运动加速度的影响而导致测量精度降低.通过将GPS加速度引入重力观测方程,有效补偿了载体运动加速度造成的姿态测量误差.利用基于重力场和地磁场矢量观测的迭代最小二乘姿态确定算法得到修正罗德里格姿态参数.姿态信息通过互补滤波器与陀螺仪测量值融合以提高动态响应.实验结果表明,该低成本姿态测量系统可明显提高机动环境下的姿态测量精度,姿态角测量误差小于3°.     

AESS: Accelerated Exact Stochastic Simulation

The Stochastic Simulation Algorithm (SSA) developed by Gillespie provides a powerful mechanism for exploring the behavior of chemical systems with small species populations or with important noise contributions. Gene circuit simulations for systems biology commonly employ the SSA method, as do ecological applications. This algorithm tends to be computationally expensive, so researchers seek an efficient implementation of SSA. In this program package, the Accelerated Exact Stochastic Simulation Algorithm (AESS) contains optimized implementations of Gillespie?s SSA that improve the performance of individual simulation runs or ensembles of simulations used for sweeping parameters or to provide statistically significant results.

Program summary

Program title: AESSCatalogue identifier: AEJW_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJW_v1_0.htmlProgram obtainable from: CPC Program Library, Queen?s University, Belfast, N. IrelandLicensing provisions: University of Tennessee copyright agreementNo. of lines in distributed program, including test data, etc.: 10 861No. of bytes in distributed program, including test data, etc.: 394 631Distribution format: tar.gzProgramming language: C for processors, CUDA for NVIDIA GPUsComputer: Developed and tested on various x86 computers and NVIDIA C1060 Tesla and GTX 480 Fermi GPUs. The system targets x86 workstations, optionally with multicore processors or NVIDIA GPUs as accelerators.Operating system: Tested under Ubuntu Linux OS and CentOS 5.5 Linux OSClassification: 3, 16.12Nature of problem: Simulation of chemical systems, particularly with low species populations, can be accurately performed using Gillespie?s method of stochastic simulation. Numerous variations on the original stochastic simulation algorithm have been developed, including approaches that produce results with statistics that exactly match the chemical master equation (CME) as well as other approaches that approximate the CME.Solution method: The Accelerated Exact Stochastic Simulation (AESS) tool provides implementations of a wide variety of popular variations on the Gillespie method. Users can select the specific algorithm considered most appropriate. Comparisons between the methods and with other available implementations indicate that AESS provides the fastest known implementation of Gillespie?s method for a variety of test models. Users may wish to execute ensembles of simulations to sweep parameters or to obtain better statistical results, so AESS supports acceleration of ensembles of simulation using parallel processing with MPI, SSE vector units on x86 processors, and/or using NVIDIA GPUs with CUDA.     

基于分级缓存加速的高可靠高速星载固存设计

星上模块在模式切换过程会因为星载固态存储器启动过程缓慢而导致无法快速访问固存。分级缓存系统设计采用片内缓存结合小容量非易失存储器(MRAM)的硬件架构,通过在MRAM中存储文件对象头索引以及Nand Flash块元数据区索引等流程优化来加速文件系统启动操作。本设计通过数据建模和仿真实验来分析性能,并在硬件板卡上进行算法实现和测试验证,以对象为索引的启动方式耗时3.12 ms,以块元数据区为依据的启动方式耗时143.47 ms。对比传统设计架构下的耗时170.35s的启动操作,基于分级缓存加速的系统具有高可靠性同时大大缩短了固存启动时间。其系统性能提升为卫星在轨管控优化提供技术基础。