Simulating the structure and dynamics of human hair: Modelling,rendering and animation

We develop and present a new approach to modelling the characteristics of human hair, considering not only its structure, but also the control of its motion and a technique for rendering it in a realistic form. The approach includes a system for interactively defining the global positioning of the strands of hair on the head. Special attention is paid to the self shadowing of the hair. A mass/spring/hinge system is used to control a single strand's position and orientation. We demonstrate that this approach results in a believable rendition of the hair and its dynamics.     

Rendering optimal solar shadows with plural sunlight depth buffers

We propose a novel method, based on the two-pass Z-buffer algorithm, to calculate shadows with sufficient precision and efficiency for rendering a daytime landscape with solar penumbrae. The special feature of the proposed method is that the shadows can be preserved with a precision superior to that of any visible surface. We use the optimal number of plural shadow buffers to do this; it gives a fairly satisfying trade–off between computation time and quality of shadows.     

An effective hybrid PSO-based algorithm for flow shop scheduling with limited buffers

In this paper, an effective hybrid algorithm based on particle swarm optimization (HPSO) is proposed for permutation flow shop scheduling problem (PFSSP) with the limited buffers between consecutive machines to minimize the maximum completion time (i.e., makespan). First, a novel encoding scheme based on random key representation is developed, which converts the continuous position values of particles in PSO to job permutations. Second, an efficient population initialization based on the famous Nawaz–Enscore–Ham (NEH) heuristic is proposed to generate an initial population with certain quality and diversity. Third, a local search strategy based on the generalization of the block elimination properties, named block-based local search, is probabilistically applied to some good particles. Moreover, simulated annealing (SA) with multi-neighborhood guided by an adaptive meta-Lamarckian learning strategy is designed to prevent the premature convergence and concentrate computing effort on promising solutions. Simulation results and comparisons demonstrate the effectiveness of the proposed HPSO. Furthermore, the effects of some parameters are discussed.     

Drawing human hair using the Wisp model

This paper presents a new powerful method for hair-image generation. A simplified computer graphics (CG) model of human hair is presented to describe and render various kinds of hair images with a small number of parameters. Practical methods for handling hair styles and for generating realistic images are presented. A notable feature of the proposed method is that it is run on the conventional z-buffer algorithm. Experiments have proven that the proposed algorithm is very useful for generating various human-hair images.     

Occlusion culling and z-fail for soft shadow volume algorithms

This paper presents a significant improvement of our previously proposed soft shadow volume algorithm for simulating soft shadows. By restructuring the algorithm, we can considerably simplify the computations, introduce efficient occlusion culling with speedups of 3–4 times, thus approaching real-time performance. We can also generalize the algorithm to produce correct shadows even when the eye is inside a shadowed region (using z-fail). We present and evaluate a three pass implementation of the restructured algorithm for near real-time rendering of soft shadows on a computer with a commodity graphics accelerator. However, preferably the rendering of the wedges should be implemented in hardware, and for this we suggest and evaluate a single pass algorithm.     

Minimizing makespan for flow shop scheduling problem with intermediate buffers by using hybrid approach of artificial immune system

In this study, three new meta-heuristic algorithms artificial immune system (AIS), iterated greedy algorithm (IG) and a hybrid approach of artificial immune system (AIS-IG) are proposed to minimize maximum completion time (makespan) for the permutation flow shop scheduling problem with the limited buffers between consecutive machines. As known, this category of scheduling problem has wide application in the manufacturing and has attracted much attention in academic fields. Different from basic artificial immune systems, the proposed AIS-IG algorithm is combined with destruction and construction phases of iterated greedy algorithm to improve the local search ability. The performances of these three approaches were evaluated over Taillard, Carlier and Reeves benchmark problems. It is shown that the AIS-IG and AIS algorithms not only generate better solutions than all of the well-known meta heuristic approaches but also can maintain their quality for large scale problems.     

Unsupervised motion detection with background update and shadow suppression

An algorithm is developed to detect moving object and suppress shadow.According to motion variations caused by some moving objects in a scene,a background update approach is proposed.The developed update method efficiently prevents undesired corruption of background and does not consider the adaptation coefficient or the learning rate used in some existing algorithms.A multi-scale wavelet transform methodology is used to segment foreground from a clutter background.The optimal selection of threshold value is automatically determined which does not require any complex supervised training or manual calibration.According to photometric invariant,a color ratio difference is proposed to suppress shadow.Some complete foreground motion object regions are extracted by integrating moving object segmentation in the multi-scale wavelet with shadow suppression in the color ratio difference.The mentioned method is less affected by the presence of moving objects in a scene.Experimental results show that the proposed approach is efficient in detecting motion objects and suppressing shadows by comparisons.     

Silicon shadow mask fabrication for patterned metal deposition with microscale dimensions using a novel corner compensation scheme

Pattern deposition of metals with controlled and microscale dimensions can be a challenging task if traditional photolithography is not a practical option. This is a particularly valid concern for the case of certain polymer substrates, which are gaining in importance in the microelectronics and related industries. Therefore, a novel design and process flow for batch fabricating low cost reusable silicon shadow masks was developed. Of note was the corner compensation scheme employed to avoid over-etching of the convex corners in the design. These shadow masks enabled deposition of metals or other suitable materials with feature sizes ranging from approximately 3 to 250 μm and were successfully utilized to form patterned metal heater lines and pads on various samples. The heaters, required for conducting thermal conductivity measurements of the underlying films/substrates using the three omega (3ω) method, showed resistance–temperature linearity, confirming theoretical estimates to within 0.2%. Moreover, the room temperature thermal conductivity of an amorphous SiO₂ film as well as a polyaniline thick film were measured, further validating the deposition through shadow mask technique.     

皮影艺术在现代服饰设计中的应用与创新

从我国皮影艺术现状和现代设计领域对传统文化的研究现状入手,分析了现代服饰设计中对传统文化元素的传承与创新的重要性,提出了以设计推动传承,以设计促进发展的观点。文章着重对皮影艺术与现代服饰设计进行融合的途径进行了分析,使其在展现出新的时代特色及民族传统文化精髓的同时,实现民间传统艺术元素在现代服饰作品中的应用与创新。     

Improvement of the evaluation of closed-loop production systems with unreliable machines and finite buffers

A closed-loop production system, or loop, is a system in which a constant amount of material flows through a single fixed cycle of workstations and storage buffers. Manufacturing processes that utilize pallets or fixtures can be viewed as loops. Control policies such as CONWIP and Kanban create conceptual loops. Gershwin and Werner (2007) developed a decomposition algorithm that accurately evaluates Buzacott type closed-loop systems of any size. However there are cases where the evaluated production rate, as a function of some system parameter, is discontinuous. Such a discontinuity may give misleading results for loop system design and optimization method. We present two modifications that improve the algorithm of Gershwin and Werner (2007). Two new special types of two-machine one-buffer building blocks are developed for the decomposition, and analytical solutions for them are found. Numerical experiments are provided to show the improvement of the evaluation accuracy as compared with the existing algorithm. The discontinuity in production rate is greatly diminished with these modifications.     

A shadow fraction method for mapping biomass of northern boreal black spruce forests using QuickBird imagery

We have developed and tested a method for mapping above-ground forest biomass of black spruce (Picea mariana (Mill.) B.S.P.) stands in northern boreal forests of eastern Canada. The method uses QuickBird images and applies image processing algorithms to extract tree shadow fraction (SF) as a predictive variable for estimating biomass. Three QuickBird images acquired over three test sites and 108 ground sample plots (GSP) were used to develop and test the method. SF was calculated from the fraction of tree shadow area over the area of a reference square overlaid on the images. Linear regressions between biomass of GSP and SF from the images for each test site resulted in R² in the range from 0.85 to 0.87 (except one case at 0.41), RMSE of 11 to 18 t/ha and bias of 2 to 5 t/ha. Statistical tests demonstrated that local regressions for the three test sites were not statistically significantly different. Consequently, a global regression was calculated with all GSP and produced R², RMSE, and bias of 0.84, 14.2 t/ha and 4.2 t/ha, respectively. While generalization of these results to extended areas of the boreal forest would require further assessment, the SF method provided an efficient means for mapping biomass of black spruce stands for three test areas that are characteristic of the northern boreal forest of eastern Canada (boreal and taiga shield ecozones).     

A probabilistic approach for foreground and shadow segmentation in monocular image sequences

This paper presents a novel method of foreground and shadow segmentation in monocular indoor image sequences. The models of background, edge information, and shadow are set up and adaptively updated. A Bayesian network is proposed to describe the relationships among the segmentation label, background, intensity, and edge information. A maximum a posteriori—Markov random field estimation is used to boost the spatial connectivity of segmented regions.     

实时毛发建模和动画

提出了基于3D晶格的毛发机械模型和机械变形方法,表现毛发串的体行为,晶格被作为粒子系统采用数学计算变形.毛发机械模型被作为与晶格模型中的各单独头发串片段弹性相关的一系列线性黏弹性晶格弹簧定义.发型足以快速实时表现,同时保留了毛发的特定行为,获得足够的多样性模拟各种复杂发型.用多项式元球模型处理毛发和身体表面之间碰撞.毛发模型具有很高的实时性能和通用性,可达到准确性和计算速度之间的最佳折中.     

Multi-Level Memory Structures for Simulating and Rendering Smoothed Particle Hydrodynamics

In this paper, we present a novel hash map-based sparse data structure for Smoothed Particle Hydrodynamics, which allows for efficient neighbourhood queries in spatially adaptive simulations as well as direct ray tracing of fluid surfaces. Neighbourhood queries for adaptive simulations are improved by using multiple independent data structures utilizing the same underlying self-similar particle ordering, to significantly reduce non-neighbourhood particle accesses. Direct ray tracing is performed using an auxiliary data structure, with constant memory consumption, which allows for efficient traversal of the hash map-based data structure as well as efficient intersection tests. Overall, our proposed method significantly improves the performance of spatially adaptive fluid simulations and allows for direct ray tracing of the fluid surface with little memory overhead.     

Cloud detection in Landsat imagery of ice sheets using shadow matching technique and automatic normalized difference snow index threshold value decision

This work presents a new algorithm designed to detect clouds in satellite visible and infrared (IR) imagery of ice sheets. The approach identifies possible cloud pixels through the use of the normalized difference snow index (NDSI). Possible cloud pixels are grown into regions and edges are determined. Possible cloud edges are then matched with possible cloud shadow regions using knowledge of the solar illumination azimuth. A scoring index quantifies the quality of each match resulting in a classified image. The best value of the NDSI threshold is shown to vary significantly, forcing the algorithm to be iterated through many threshold values. Computational efficiency is achieved by using sub-sampled images with only minor degradation in cloud-detection performance. The algorithm detects all clouds in each of eight test Landsat-7 images and makes no incorrect cloud classifications.     

Modelling and animating faces using scanned data

This paper extends a physically-based approach to the realistic modelling and animation of human heads using scanned data. A three-step procedure is proposed which begins with geometry and colour data acquired from a subject's head using a radial laser scanner, continues with the construction of a 3D model of the head with complete colour texture mapping, and culminates in real-time, interactive facial animation. First, an adaptive meshing technique is described that creates non-uniform facial meshes from the densely sampled data. These geometrically accurate facial meshes adapt to features of interest in the data, increasing polygon density over articulate face regions and areas of high curvature. Secondly, the mesh is transformed into a physically-based head model of the subject. This incorporates a physical approximation to facial tissue and a set of anatomically-motivated facial muscle actuators. Finally, these components are integrated in a facial modelling and animation system.     

虚拟环境中池塘雨景雪景的构造与绘制

虚拟环境中的池塘雨景、雪景能增强人在虚拟环境中的沉浸感.如何对雨滴、雪片的运动建模,以及怎样实现其在计算机上的动态模拟,是室外仿真领域需要解决的重要问题.在粒子系统中引入粒子的运动模型,通过修改运动模型中粒子质量、风速和风向等关键参数的取值,实现了在不同风吹动条件下雨滴、雪片随风飞舞的实时模拟;同时通过对雨滴、雪片下落位置的判断,在其与池塘水面的接触点,利用特殊的幅度值平均算法实现了池塘水面受到粒子扰动后所产生的波动效果;最后通过读取外部模型参数的信息,生成了池塘周围的辅助景观.绘制的结果证明这些构造和绘制方法是有效可行的.     

Monolithic Friction and Contact Handling for Rigid Bodies and Fluids Using SPH

We propose a novel monolithic pure SPH formulation to simulate fluids strongly coupled with rigid bodies. This includes fluid incompressibility, fluid–rigid interface handling and rigid–rigid contact handling with a viable implicit particle-based dry friction formulation. The resulting global system is solved using a new accelerated solver implementation that outperforms existing fluid and coupled rigid–fluid simulation approaches. We compare results of our simulation method to analytical solutions, show performance evaluations of our solver and present a variety of new and challenging simulation scenarios.     

A general framework for three-dimensional surface reconstruction by self-consistent fusion of shading and shadow features

In this paper a novel framework for three-dimensional surface reconstruction by self-consistent fusion of shading and shadow features is presented. Based on the analysis of at least two pixel-synchronous images of the scene under different illumination conditions, this framework combines a shape from shading approach for estimating surface gradients and altitude variations on small scales with a shadow analysis method that allows for the determination of the large-scale properties of the surface. As a first step, the result of shadow analysis is used for selecting a consistent solution of the shape from shading reconstruction algorithm. As a second step, an additional error term derived from the fine-structure of the shadow is incorporated into the reconstruction algorithm. This approach is extended to the analysis of two or more shadows under different illumination conditions leading to an appropriate initialization of the shape from shading algorithm. The framework is applied to the astrogeological task of three-dimensional reconstruction of regions on the lunar surface using ground-based CCD images and to the machine vision task of industrial quality inspection.     

带不相关并行机和有限缓冲MHFS调度的混合启发式算法

研究每阶段含不相关并行机的多阶段混合流水车间问题(MHFSP),工件的加工时间取决于所分配的机器,相邻阶段之间缓冲区能力有限.鉴于直接求解该NP-hard问题较为困难,将其转化为带阻塞和不相关并行机的MHFSP (BMHFSP-UPM),建立整数规划模型,基于遗传算法(GA)和禁忌搜索(TS)提出一种混合启发式算法(HHGA&TS)进行求解.在该算法中,设计基于多阶段并行加工的二维矩阵编码方案,继而基于二维矩阵元胞组的初始解群体表述设计参数自适应策略;引入基于工件位-基因位的单点倒置交叉以及基于机器号的单点变异过程,利用GA求解机制完成解更新过程;设计机器号次序交换(MNE)、工件位置交换(JNE)、工件工序变异(JNM)三种邻域解移动规则,从而完成基于MNE-JNE-JNM的TS二次优化.仿真实验测试了多达120个工件的720组不同规模实例,结果表明,相较于GA、TS及NEH-IGA,所提出的混合启发式算法在解的质量方面表现更佳.