虚拟展览馆系统中冲突检测的实现

冲突检测是虚拟环境系统中一个重要的基本功能模块。也是给用户提供真实感的重要手段之一。然而，它的实现往往伴随着大量的资源开销。该文介绍了虚拟展览馆系统中采用的基本冲突检测算法。以及作出的改进；并阐述了在此基础上构造的一个基于层次场景的冲突检测功能模块。提出了一个基于场景的连续冲突检测方法。实验结果表明虚拟展览馆系统中的冲突检测功能部件能较为理想地检测出场景中三维物体移动中的冲突情况。     

柔性物体仿真的研究

柔性物体的模拟是计算机图形学的一个研究课题,同时非常重要和前沿。在人们的日常生活中,柔性物体无处不在,处处可见,如流水、绳索、织物等,如何利用计算机高效灵活复原柔性物体在现实中的运动是计算机图形学的挑战。该文分析柔性物体仿真的两种技术几何模型、物理模型法的优缺点,以及简要介绍冲突检测与响应。     

柔性物体仿真的研究

柔性物体的模拟是计算机图形学的一个研究课题,同时非常重要和前沿。在人们的日常生活中,柔性物体无处不在,处处可见,如流水、绳索、织物等,如何利用计算机高效灵活复原柔性物体在现实中的运动是计算机图形学的挑战。该文分析柔性物体仿真的两种技术几何模型、物理模型法的优缺点,以及简要介绍冲突检测与响应。     

RegLang监管合约规则冲突检测方法

RegLang是一种面向监管规则设计的智能合约编程语言，旨在支撑监管规则数字化与合约化，已在金融等领域取得初步应用。然而，在实际应用中，金融监管领域的“适用冲突”“多轨规制”等规则冲突问题可能对区块链金融应用造成严重影响，在增加从业机构合规成本的同时，对监管合约的有效性带来挑战。针对上述问题，提出监管合约变量类型依赖分析方法与基于依赖图的变量类型传播分析方法，推断监管合约中所有变量的可能类型，并根据可满足性模理论求解器支持的符号类型实现监管合约中变量、语句和规则的符号化。基于符号分析的规则冲突检测方法，将监管规则冲突问题转换为可满足性问题，从而检测监管合约中规则的自冲突、完全冲突和局部冲突，并针对多个监管规则间完全冲突检测中的状态空间爆炸问题提出子集划分算法进行优化。实验结果表明，RegLang监管合约规则冲突检测方法可以有效检测各类监管规则冲突，在对代码行数为300行的监管规则进行冲突检测时，自冲突、完全冲突和局部冲突的平均检测耗时分别为1 234.9 ms、1 977.8 ms和2 364.5 ms，在实际应用中是可接受的，能够为实现监管规则数字化提供有效保障。     

一种无线动态位移在线监测系统的研究与设计

研究设计了一种动态位移在线监测系统,可以测量物体的某个表面或某点相对于参考表面或参考点之间的距离或位置的变化,广泛应用于物体容积形变、橡胶生产中橡胶厚度以及容积表面形变等的在线监控.位移传感器由安装伸缩尺的位移探测单元、信息处理单元、无线传输单元、电源管理单元及面板控制单元组成.伸缩尺内部有弹簧,当尺头接触被测物时,尺子由于弹簧弹力缩进,当尺头离开被测物时,尺子自动伸长.信息处理单元是将尺子的伸缩信息转换成数字信息,然后通过面板显示出来,亦可通过无线传输模块将数据发送到远程监控主机.本系统的研究与设计为相关应用提供了一种新型动态位移测量的方法和设备,具有重要的经济及社会价值.     

基于XACML的策略冲突检测与消解方法

基于XACML(extensible access control markup language)的访问控制策略在云计算服务中得到广泛使用,其存在的问题也日益凸显,策略集的冲突检测与冲突消解问题就是其中之一。然而,目前学术界在冲突消解方面研究较少,现有的研究也仅能对冲突进行逐对消解,没有针对大量冲突的一次性消解方法,这在大规模云计算环境中是很难适用的。针对这个问题,从算法的角度出发,改进了原有的策略冲突检测方法,并设计了一种新的策略冲突一次性消解算法。该算法将安全规则映射到N维空间中,每一个维度表示一个属性,将定义复杂的安全策略在每一个属性上统一表示为几种基本数据类型的属性值集合,通过对简单集合的交集运算来进行冲突和冗余检测。在冲突消解时,将所有的冲突汇集到一起,运用有向无环图的拓扑排序来计算规则优先级,按优先级的顺序为每个规则构建一棵空间区域选择树,选取其对应的消解后的N维空间区域,完成大量冲突的一次性消解。实验表明,冲突检测和一次性消解算法是正确、高效和可行的。     

基于三角剖分和纹理映射的物体表面重建算法

提出一种简便的物体表面重建算法,该算法用立体匹配获得的物体表面三维特征点和原匹配图像来重建物体的真实表面,主要步骤是:将物体表面三维特征点集映射到某个平面上,在此平面上完成三角剖分,将剖分的结果映射回物体表面,用空间三角片来表示物体的几何模型,最后在OpenGL环境下将物体原匹配图像贴到几何模型上,这样就真实地重建了物体表面.最后给出了重建物体真实表面的所需条件.     

货叉运动机械冲突光电型检测装置

为了准确检测堆垛机货叉伸缩时是否与其他物体发生机械冲突,防止冲突造成损害,设计了一种无连线型机械冲突检测装置.装置由偏振滤波型光电传感器、梳齿挡块和多块反射板构成.安装在货叉侧面可滑动的梳齿挡块与物体发生冲突时将遮挡反射板.光电传感器通过检测反射板是否被遮挡来检测是否发生机械冲突.相对于基于摩擦离合器、过流检测以及以往的光电检测和保护方式,该装置不易漏检误检,且与货叉无连线.     

基于交互式方法的飞行器短期冲突检测模型

为了提高航空器的短期冲突检测的准确性和可靠性,对传统算法与模型进行了研究,在此基础上设计了具有机动检测的交互式UKF算法,提出了短期冲突检测模型。该模型对飞行器的航迹进行了分析,然后对飞行器的冲突域检测、冲突脱离、机动检测和冲突确认进行了讨论,并根据该模型设计了冲突检测算法。仿真结果表明,该算法能够精确、实时的检测飞行器的航迹,克服了传统算法的冲突盲警告和轨迹不变问题,提高了冲突预警的准确性,为管制员提供了可靠的保障。     

基于PERT图的冲突检测的研究

冲突是协同设计过程中一个不可避免的实际问题,产生的原因是协同设计环境下不同设计群体之间存在各个方面的差异性。基于以上原因,提出了一种冲突检测模型,并在此基础上提出了冲突的分类和基于PERT图的冲突检测算法,此方法通过组合不同设计者的设计方案PERT图找出他们之间存在的冲突问题,进而进行消解。最后通过实例验证此方法的有效性。     

基于线性规划的碰撞检测算法研究

介绍了虚拟环境中一种基于凸多面体面信息对偶线性规划模型(DualModel)的快速旋转和移动物体之间干涉碰撞实时检测方法。该文详细介绍了建模过程和求解步骤,物体由构成凸多面体的三角形面信息表示,而物体的运动由一组虚拟现实环境中的全局移动和旋转矩阵表示。这种数学编程方法具有数据结构简单、算法可靠和速度快等优点,同时能够很好地解决高速(运动帧)碰撞的问题。这一方法通过使用主-对偶(primal-dual)内点方法来解线性规划方程,具有很好的效果,能够检测多物体对之间的碰撞。实验结果表明,基于数学编程的方法相对两种著名的工具包I-COLLIDE和SOLID,具有速度快和稳定可靠的优点,而I-COLLIDE和SOLID工具包基于两种著名的算法:LinCanny(LC)最近特征算法和GJK算法(EnhancedGilbertJohnsonandKeethialgorithm)。     

Fast Collision Detection Algorithms with Applications to Particle Flow

In this paper, we present efficient algorithms for collision detection of arbitrarily shaped rigid moving objects in a variety of interactive as well as non-interactive environments. The algorithms primarily consist of two stages. The first stage involves finding candidate objects for possible collisions. The second stage involves detecting exact (within a prespecified tolerance) collision between these candidates. The primary data structure used in the algorithms is an octree. In the first stage, we build an octree for the enclosure containing the objects, which is used to detect possible collisions. Assuming spatial/temporal coherence i.e., that the particles move slowly or that the time sampling is fast enough, the average time complexity of this stage can be shown to be O(n) (excluding the time complexity for a one time octree construction), where n is the number of particles. In the second stage, we build a surface-octree for each object. If the objects are convex and assuming coherence, the expected time complexity to detect precise (within a prespecified tolerance) collision for each pair is a constant (excluding the time complexity for a one time surface-octree construction). Therefore, the overall expected time complexity for convex object collision detection is linear with respect to n. For the concave objects, complexity analysis is nontrivial to perform and instead we provide a very practical (almost linear time) algorithm. We apply our algorithms to particle flow simulations by simulating flow density conditions often arising in granular flows.     

Fast collision detection between complex solids using rasterizing graphics hardware

We present an efficient method for detecting collisions between complex solid objects. The method features a stable processing time and low sensitivity to the complexity of contact between objects. The algorithm handles both concave and convex objects; however, the best performance is achieved when at least one object is convex in the proximity of the collision zone (our techniques check the required convexity property as a byproduct of the calculations). The method achieves real-time performance when calculations are supported by the standard functionality of graphics hardware available on high-end workstations.     

Effectiveness and driver acceptance of a semi-autonomous forward obstacle collision avoidance system

This paper proposes a semi-autonomous collision avoidance system for the prevention of collisions between vehicles and pedestrians and objects on a road. The system is designed to be compatible with the human-centered automation principle, i.e., the decision to perform a maneuver to avoid a collision is made by the driver. However, the system is partly autonomous in that it turns the steering wheel independently when the driver only applies the brake, indicating his or her intent to avoid the obstacle. With a medium-fidelity driving simulator, we conducted an experiment to investigate the effectiveness of this system for improving safety in emergency situations, as well as its acceptance by drivers. The results indicate that the system effectively improves safety in emergency situations, and the semi-autonomous characteristic of the system was found to be acceptable to drivers.     

一种快速计算三维空间中物体碰撞接触面的方法

介绍了一种利用三维空间中物体运动的时空相关性 ,以碰撞检测取得的两物体碰撞三角面为计算域 ,快速寻找凸多面体发生碰撞时接触面的方法。该方法利用特征点来描述接触面 ;根据接触面的拓扑结构计算碰撞三角面间的点 -面、边 -边的最小距离 ,从而快速确定碰撞位置、接触面特征点及接触面的法线 ,并简要叙述了点 -面、边 -边接触的计算流程。该方法通过缩小接触面的计算范围 ,简化接触面法线 ,提高了碰撞测定的实时性。通过实际应用 ,证明了该方法的可行性 ,适用于三维游戏制作、虚拟现实中的物理仿真等各项应用研究。     

一个计算凸多面体间碰撞点的快速算法

计算两个物体之间的碰撞点是碰撞响应的基础,也是一项系统开销很大的任务.因此,研究碰撞点快速求解算法对碰撞响应的实时性具有重要意义.该文提出了一个算法,当在虚拟环境中检测到碰撞时,应用此算法可以在碰撞响应之前快速计算出两个物体之间的准确碰撞时间,并能计算出此时两个物体之间的碰撞点.     

虚拟现实中手与虚拟物体碰撞检测的一种算法

在虚拟现实技术中，人与虚拟空间物体的碰撞检测是非常重要的研究课题之一。由于空间物体结构的复杂性和碰撞响应的多样性，故找出一种通用检测算法是极为困难的。该文针对飞机机舱内的可操纵物体：开关，按钮，油门杆，停车杆等，实现了一种实时精确的碰撞检测算法。     

Distant Collision Response in Rigid Body Simulations

We use a finite element model to predict the vibration response of objects in a rigid body simulation, such that rigid objects are augmented to provide a plausible elastic collision response between distant objects due to vibration. We start with a generalized eigenvalue decomposition of the elastic model to precompute a response to an impact at any point on an elastic object with fixed boundary conditions. Then, given a collision between objects, we generate an approximate response impulse to distribute to other objects already in contact with the colliding bodies. This can lead to distant impacts causing an object to slip, or a delicate stack of objects to fall. We also use a geodesic distance based spatial attenuation approximation for travelling waves in objects to respond to an impact at one contact with an impulse at other locations. This response ultimately allows a long distance relationship between contacts, both across a single object being struck, but also traversing the contact graph of a larger collection of objects. We qualitatively validate our approach with a ground truth simulation, and demonstrate a number of scenarios where a long distance relationship between contacts is valuable.     

Real-time knot-tying simulation

The real-time simulation of rope, and knot tying in particular, raises difficult issues in contact detection and management. Some practical knots can only be achieved by complicated crossings of the rope, yielding multiple simultaneous contacts, especially when the rope is pulled tight. This paper describes a graphical simulator that allows a user to grasp and smoothly manipulate a virtual rope and to tie arbitrary knots, including knots around other objects, in real time. A first component of the simulator computes the global configuration of the rope based on user interactions. Another component of the simulator precisely detects self-collisions in the rope as well as collisions with other objects. Finally, a third component manages collisions to prevent penetration, while making the rope slide with some friction along itself and other objects, so that knots can be pulled tight in a realistic manner. An additional module uses recent results from knot theory to identify, also in real time, which topological knots have been tied. This work was motivated by surgical suturing, but simulation in other domains, such as sailing and rock climbing, could also benefit from it.     

VoxColliDe: Voxel collision detection for virtual environments

Collision detection is fundamental in achievingnatural dynamics in virtual environments, but current algorithms are too slow, causing a major bottleneck in processing and hindering the building of interactive simulation environments. This paper provides an overview of the collision detection problem and current attempted solutions. A voxel-based approach to rigid-body collision detection is presented, with its potential high performance explained.Voxel collision detection takes place on a pair-wise basis, involving two additional representations of a polygonal object, a Voxmap and a Point Shell. These are constructed in a pre-processing step and allow fast collision detection through a simple look-up reference of points into voxels. Collision performance depends upon the number of points in the shell, and can trade accuracy for speed. A range ofpruning techniques, needed to cut down the number of objects undergoing collision testing, are reviewed and implemented. These allow most effective use of the voxel collision detection algorithm in multi-body simulations, such as virtual environments.Performance evaluations demonstrate the voxel collision detection algorithm's ability to achieve interactive rates (above 20 Hz) for both high precision pair-wise collision tests, and for large numbers of objects in multi-body environments. The voxel collision detection algorithm is suitable for parallel, hardware implementation. This provides the potential for great enhancements to already extremely high performance, rendering the voxel-based approach to collision detection all the more promising.