Interactive Simulation of Rigid Body Dynamics in Computer Graphics

Interactive rigid body simulation is an important part of many modern computer tools, which no authoring tool nor game engine can do without. Such high‐performance computer tools open up new possibilities for changing how designers, engineers, modelers and animators work with their design problems. This paper is a self contained state‐of‐the‐art report on the physics, the models, the numerical methods and the algorithms used in interactive rigid body simulation all of which have evolved and matured over the past 20 years. Furthermore, the paper communicates the mathematical and theoretical details in a pedagogical manner. This paper is not only a stake in the sand on what has been done, it also seeks to give the reader deeper insights to help guide their future research.     

Sparse Localized Decomposition of Deformation Gradients

Sparse localized decomposition is a useful technique to extract meaningful deformation components out of a training set of mesh data. However, existing methods cannot capture large rotational motion in the given mesh dataset. In this paper we present a new decomposition technique based on deformation gradients. Given a mesh dataset, the deformation gradient field is extracted, and decomposed into two groups: rotation field and stretching field, through polar decomposition. These two groups of deformation information are further processed through the sparse localized decomposition into the desired components. These sparse localized components can be linearly combined to form a meaningful deformation gradient field, and can be used to reconstruct the mesh through a least squares optimization step. Our experiments show that the proposed method addresses the rotation problem associated with traditional deformation decomposition techniques, making it suitable to handle not only stretched deformations, but also articulated motions that involve large rotations.     

On‐the‐fly generation and rendering of infinite cities on the GPU

In this paper, we present a new approach for shape‐grammar‐based generation and rendering of huge cities in real‐time on the graphics processing unit (GPU). Traditional approaches rely on evaluating a shape grammar and storing the geometry produced as a preprocessing step. During rendering, the pregenerated data is then streamed to the GPU. By interweaving generation and rendering, we overcome the problems and limitations of streaming pregenerated data. Using our methods of visibility pruning and adaptive level of detail, we are able to dynamically generate only the geometry needed to render the current view in real‐time directly on the GPU. We also present a robust and efficient way to dynamically update a scene's derivation tree and geometry, enabling us to exploit frame‐to‐frame coherence. Our combined generation and rendering is significantly faster than all previous work. For detailed scenes, we are capable of generating geometry more rapidly than even just copying pregenerated data from main memory, enabling us to render cities with thousands of buildings at up to 100 frames per second, even with the camera moving at supersonic speed.     

IISPH‐FLIP for incompressible fluids

We propose to use Implicit Incompressible Smoothed Particle Hydrodynamics (IISPH) for pressure projection and boundary handling in Fluid‐Implicit‐Particle (FLIP) solvers for the simulation of incompressible fluids. This novel combination addresses two issues of existing SPH and FLIP solvers, namely mass preservation in FLIP and efficiency and memory consumption in SPH. First, the SPH component enables the simulation of incompressible fluids with perfect mass preservation. Second, the FLIP component efficiently enriches the SPH component with detail that is comparable to a standard SPH simulation with the same number of particles, while improving the performance by a factor of 7 and significantly reducing the memory consumption. We demonstrate that the proposed IISPH‐FLIP solver can simulate incompressible fluids with a quantifiable, imperceptible density deviation below 0.1%. We show large‐scale scenarios with up to 160 million particles that have been processed on a single desktop PC using only 15GB of memory. One‐ and two‐way coupled solids are illustrated.     

垂直管中油,气,水三相流总流量测量模型研究

基于集流型涡轮流量计与放射性低能源密度—持水率计在大庆生产测井研究所油、气、水三相流动环路中的实验响应结果，首先考察了用于气液两相流中涡轮流量计的Ａｙａ物理模型，进而提出了经过校正后用于确定油、气、水三相流总流量的测量模型，用此模型预测三相流总流量与流动环标定数据对比后其误差小于５％，满足了石油工业应用要求     

促进三峡库区和谐稳定发展评价方法研究

三峡库区已完成了百万移民的搬迁安置,进入了移民安稳致富的新阶段,库区社会和谐稳定对促进库区经济社会健康发展和实现全面建成小康社会的目标具有重要作用。本研究重点关注和谐库区建设思路及评价指标体系构建:一方面,从理论层面,重点论述与库区和谐社会相关的理论认识成果;另一方面,从实际管理运用层面,构建了库区和谐评价指标体系,可为移民动态管理提供有力的技术支撑。     

2016年长江第1号洪水预报及调度影响分析

通过分析2016长江第1号洪水的水雨情发展、洪水组成、水情预报、调度还原计算成果等,解析了该场洪水的暴雨洪水特性、预报对调度的支撑作用以及三峡水库调度对城陵矶河段水位的影响。分析表明：金沙江、乌江来水对第1号洪水起筑底作用,三峡区间洪水则为该场洪水造峰,三者最大1d洪量占三峡入库来水比率分别达26.1%,15.6%,38.1%;第1号洪水期间,水情预报为调度决策提供了长预见期、较高精度的前提支撑,78,54,30,6 h预见期的三峡入库洪峰预报误差分别仅为-20.0%,-10.0%,-4.0%,0;三峡水库在第1号洪水期间通过防洪调度将入库洪峰流量削峰38%,最大拦蓄洪量约29亿m3,削减莲花塘站洪峰水位0.39 m左右,避免了城陵矶河段出现超保证水位。     

库水升降速率对老蛇窝滑坡稳定性影响分析

通过监测资料分析和滑坡稳定性数值计算,探讨了三峡库水位在不同升降速率下对老蛇窝滑坡稳定性的影响规律。研究结果表明,理论上库水位上升有利于老蛇窝滑坡的稳定,但实际运行中库水位上升是不利于滑坡稳定的,因为库水浸泡会使滑坡前缘塌岸;老蛇窝滑坡为动水压力型滑坡,最主要诱发因素为库水位的下(骤)降;老蛇窝滑坡稳定性的临界库水位调度速率为0.9 m/d,即当库水位下降速率大于0.9 m/d时,滑坡K值小于1。     

Differential geometry properties of lines of curvature of parametric surfaces and their visualization

We present algorithms for computing the differential geometry properties of lines of curvature of parametric surfaces. We derive a unit tangent vector, curvature vector, binormal vector, torsion, and algorithms to evaluate their higher-order derivatives of lines of curvature of parametric surfaces. Among these quantities, it is shown that the curvature and its first derivative of the lines of curvature lend a hand for the formation of curved plates in shipbuilding. We also visualize the twist of lines of curvature, which enables us to observe how much the osculating plane of the line of curvature turns about the tangent vector.     

ASSESSMENT OF RED BLOOD CELL DEFORMABILITY BY CENTRIFUGAL SEDIMENTATION

A centrifugal sedimentation method (CSM) is proposed for the assessment of deformability of red blood cells. The method is based on the premise that a red blood cell (RBC) should deform in a centrifugal field due to the variation of the centrifugal acceleration with the distance from the center of rotation. This change in shape of the RBC leads to a change in the rate of sedimentation in the centrifugal field. The rate of sedimentation, which serves as a measure of deformability, is characterized by an apparent sedimentation coefficient (ASC) and its normalized value (NASC), which is calculated by comparison with a control group of normal RBCs. It has been shown that the NASC is sensitive to the speed of rotation, to treatments with glutaraldehyde, diamide, or chlorpromazine, to heat treatment and to osmotic pressure variations.