Guijuan Zhang

Skeleton-based control of fluid animation

We present a skeleton-based control method for fluid animation. Our method is designed to provide an easy and intuitive control approach while producing visually plausible fluid behavior. In our method, users are allowed to control animated fluid with skeleton keyframes. Expected results are then obtained by driving fluid towards a sequence of targets specified in these keyframes. In order to solve for an optimal driving solution, we propose a keyframe matching model based on the transportation principle. Moreover, to ensure that the fluid actors move as rigid bodies while preserving liquid properties during animation, we introduce an approach of driving solid-like liquid motion. Finally, we embed the skeleton-based control method into the standard fluid animation, and apply it to control fluid actors’ motion as well as liquid shape deformation. Experimental results show that our method can generate natural-looking interesting fluid behavior with little additional cost.

Rigid‐motion‐inspired liquid character animation

We present a rigid‐motion‐inspired method for animating liquid characters in this paper. Our method allows an animator to control the motion of liquid characters with motion capture data that is widely used in rigid body animation. It animates the most visual interesting part of liquid character, that is, to preserve characters shape as well as produce enough liquid details. To this end, we build a two‐layer model to represent the character by two coaxial layers: the rigid kernel and the liquid shell. Different control paradigms are used for the two layers instead of applying homogeneous force that is common in previous approaches. By embedding the control algorithm to the Navier–Stokes equations, we compute the fluid velocity that drives the motion of the liquid character. Results show that the method is easy and intuitive to use while incurring little additional cost.Copyright

Visualization of fluid simulation: An SPH-based multi-resolution method: Visualization of fluid simulation: An SPH-based multi-resolution method

Fluid simulation is an important research topic since it is widely used in virtual training, education, computer games, and digital entertainment. Generating fluid simulation results with high degree of visual realism is challenging in these applications. We present a visualization approach for fluid simulation in this paper. Our method allows students to understand the complex natural phenomena so as to solve the fluid engineering problems intuitively. In this study, an SPH (Smoothed Particle Hydrodynamics)‐based multi‐resolution method is proposed for fluid simulation. The method can keep the accuracy while improve the efficiency significantly. We construct a multi‐resolution fluid model from bottom to top by combining fluid computation and surface reconstruction. We first compute multi‐resolution particles with a novel adaptive SPH model in the bottom layer. Next, surface particles are extracted and pre‐processed to provide samples for surface extraction. Then, the multi‐resolution surface reconstruction model is built in the top layer. Meshes from different reconstruction resolutions are merged to obtain the final fluid surface. Experimental results show that our approach can effectively represent multi‐scale fluid details and efficiently produce visual‐pleasing fluid simulation results.

A grouping approach based on non-uniform binary grid partitioning for crowd evacuation simulation

Small social groups based on kinship or friendships are ubiquitous in human crowds. Therefore, the effect of social groups on crowd evacuations and that of crowd evacuations on social groups must be investigated. To simulate the group phenomenon when an emergency occurs, we propose an improved social force model that takes into account the social group relationship among the population, and based on our proposed model, a novel grouping algorithm predicated on non‐uniform binary grid partitioning is put forward. The approach initially maps the individuals into the plane space, and then it adopts top‐down binary grid partitioning iteratively until the divided grid contains only the individuals with relations; then, the values of the relation and density of the non‐empty grid cells are calculated, and the grids are sorted according to these values. After sorting, selecting, merging, and forming the core grids, the other grids are merged to the core grids. We have compared the algorithm with the hierarchical classification algorithm and the grid‐based algorithm. The results show that the accuracy, speed, and scalability are all advantages. We also establish a simulation platform to illustrate the proposed grouping algorithm and the improved social force model for crowd evacuation simulation.

An efficient parallel method for photo-realistic fluid animation

ABSTRACTFluid animation often appears in applications such as games, films and cartoons. How to animate photo-realistic fluid motion efficiently is an important issue. We present an efficient parallel method for photo-realistic fluid animation in this paper. Our method is designed to generate fluid animation results with high efficiency on a cluster system. To do this, we categorize the computers in our cluster system into two classes, the server and the client. The server controls the process of the fluid animation while the clients are responsible for numerical computation. Given 3D virtual environment and fluid initial condition, we make pre-processing on the server so as to decompose the fluid animation task into several subtasks. Thus, the computation domain is divided into blocks and each client executes numerical computation for one block. The blocks of two adjacent clients are overlapped to keep the continuity of the solution across subdomain interface. We demonstrate the efficiency of our method ...

A visualization method in virtual educational system

We present a visualization-based knowledge expression approach for virtual educational system in this paper. Our method allows teachers and students to understand complex algorithms and procedures more intuitively and conveniently during the process of teaching and learning. We take the decision tree and the random forest algorithm in the field of Data mining as examples in this paper. In our method, the decision tree is represented by a virtual 3D tree model that both the structure and the classification results can be showed clearly. In addition, random forest is represented by a group of virtual 3D trees and their positions denote the similarity between the decision trees. We also provide several user-interaction tools in our system. The tools help users to browse the forest, select a tree, delete a tree and even see the detail information of the decision tree. The effective and understandable results show the feasibility of applying visualization method in virtual educational system.

Animation of the Biological Pollutants Propagation on Large-Scale Water Surface

We present a method to animate the propagation of biological pollutants (e.g., algae, water hyacinth etc.) on large-scale water surface. In this paper, we focus on the clusters and large patches of aquatic plants rather than each single aquatic plant. The interface between water surface and the patches is represented by 2D dynamic curve. We present a 2D level set based model to animate the dynamic evolution and propagation of the interface. To handle boundaries in large-scale virtual environment, we propose a 2D voxelization method which provides the boundary condition for the level set based propagation model. Finally, we simulate the algae propagation phenomenon in Taihu Lake. The application results show that our method is intuitively implemented and convenient to produce visually interesting results.

On Exploring the Secure Connectivity of Wireless Ad Hoc Networks

Connectivity of Wireless Ad hoc Networks (WANETs) has received considerable attention in the past several years. In WANETs, achieving a secure connectivity is more challenging since all the communications should operate on secure links. In this paper, we investigate the characterization of the critical density λ c for Poisson random geometric graphs which is the central problem of secure connectivity. By combining the continuum percolation theory with the clustering coefficient method, we derive a tighter lower bound on λ c which provides fundamental understanding on the secure connectivity of WANETs.