Smooth interpolation on homogeneous matrix groups for computer animation

Homogeneous matrices are widely used to represent geometric transformations in computer graphics, with interpo- lation between those matrices being of high interest for computer animation. Many approaches have been proposed to address this problem, including computing matrix curves from curves in Euclidean space by registration, representing one-parameter curves on manifold by rational representations, changing subdivisional methods generating curves in Euclidean space to corresponding methods working for matrix curve generation, and variational methods. In this paper, we propose a scheme to generate rational one-parameter matrix curves based on exponential map for interpolation, and demonstrate how to obtain higher smoothness from existing curves. We also give an iterative technique for rapid computing of these curves. We take the computation as solving an ordinary differential equation on manifold numerically by a generalized Euler method. Furthermore, we give this algorithm’s bound of the error and prove that the bound is proportional to the shift length when the shift length is sufficiently small. Compared to direct computation of the matrix functions, our Euler solution is faster.

Schematic interface of sound creation for computer animators

As an audiovisual medium, computer animations require superior image quality and professional soundtrack to lead audiences into their fascinating virtual world. Without sound, the impact of storytelling is reduced or the story is even not under- standable. Despite the importance of sound, most animators are unfamiliar with sound editing software. Limited budget projects such as independent or student works have difficulty hiring sound professionals to create tailor-made soundtrack. Therefore, we need a suitable sound tool to express their individual ideas. In this paper, we propose an approach using schematic for both computer animation and sound. Our approach provides (1) physical simulation on sound through animation parameters and (2) a new channel for animators to add aesthetic values in sound through their experience of using schematics in existing animation software. We demonstrate our idea through several examples, such as Doppler shift, obstacle effect, importance, energetic, and sputtering effect.

Modeling heterogeneous behaviors with different strategies in a terrorist attack

Existing simulations of terrorist attacks do not consider individual variations.To overcome this lim-itation,we propose a framework to model heterogeneous behavior of individuals during terrorist attacks.We constructed an emotional model that integrated personality and visual perception for pedestrians.The emotional model was then integrated with pedestrian relationship networks to establish a decision-making model that sup-ported pedestrians’altruistic behaviors.A mapping model has been developed to correlate antisocial personality traits with attack strategies employed by terrorists.Experiments demonstrate that the proposed algorithm can generate practical heterogeneous behaviors that align with existing psychological research findings.

Study on Virtual Human Skeleton System

A solution of virtual human skeleton system is proposed. Some issues on integration of anatomical geometry, biodynamics and computer animation are studied. The detailed skeleton system model that incorporates the biodynamic and geometric characteristics of a human skeleton system allows some performance studies in greater detail than that performed before. It may provide an effective and convenient way to analyze and evaluate the movement performance of a human body when the personalized anatomical data are used in the models. An example shows that the proposed solution is effective for the stated problems.

A motion retargeting algorithm based on model simplification

A new motion retargeting algorithm is presented, which adapts me motion capture data to a new character. To make the resulting motion realistic, the physically-based optimization method is adopted. However, the optimization process is difficult to converge to the optimal value because of high complexity of the physical human model. In order to address this problem, an appropriate simplified model automatically determined by a motion analysis technique is utilized, and then motion retargeting with this simplified model as an intermediate agent is implemented. The entire motion retargeting algorithm involves three steps of nonlinearly constrained optimization： forward retargeting, motion scaling and inverse retargeting. Experimental results show the validity of this algorithm.

ANGULAR VELOCITY INTERPOLATION USING QUATERNION

In simulation,sometimes we wish to stipulate a specified angular velocity applied to a given frame.Although position,linear velocity and orientation interpolations are well studied,less attention is paid on angular velocity interpolation.In this paper,a new method to smoothly interpolate angular velocity using quaternions is presented.This method can be easily incorporated into a key frame animation system.The angular velocity at an arbitrary time can be calculated easily by our method.This method can also be generalized to smoothly interpolate orientations.

A Knowledge Representation Model for Video-Based Animation

In this papert a brief survey on knowledge-based animation techniques is given.Then a VideoStream-based Knowledge Representation Model (VSKRM) for Joint Objects is presented which includes the knowledge representation of: Graphic Object,Action and VideoStream. Next a general description of the UI framework of a system is given based on the VSKRM model. Finally a conclusion is reached.

Surface Tension Model Based on Implicit Incompressible Smoothed Particle Hydrodynamics for Fluid Simulation

In order to capture stable and realistic microscopic features of fluid surface, a surface tension and adhesion method based on implicit incompressible SPH （smoothed particle hydrodynamics） is presented in this paper. It gives a steady and fast tension model and can solve the problem of not considering adhesion. Molecular cohesion and surface minimization are considered for surface tension, and adhesion is added to show the microscopic characteristics of the surface. To simulate surface tension and adhesion stably and efficiently, the surface tension and adhesion model is integrated to an implicit incompressible SPH method. The experimental results show that the method can better simulate surface features in a variety of scenarios compared with previous methods and meanwhile ensure stability and efficiency.

Simulation of Waters

This paper presents a model of the waters based on the hydraulic equations.Conditioning the initial values of the equations and solving the equations by finite-difference method, many kinds of waters and waves can be simulated,such as torrents, ripples, tides, the dam breach flood and tidal bores. Rendered examples are given and described.

Geometric Deformations Based on 3D Volume Morphing

This paper presents a new geometric deformation method based on 3D volume morphing by using a new concept called directional polar coordinate. The user specifies the source control object and the destination control object which act as the embedded spaces. The source and the destination control objects determine a 3D volume morphing which maps the space enclosed in the source control object to that of the destination control object. By embedding the object to be deformed into the source control object, the 3D volume morphing determines the deformed object automatically without the tiring moving of control points. Experiments show that this deformation model is efficient and intuitive, and it can achieve some deformation effects which are difficult to achieve for traditional methods.