Perception-based animation rendering

In most currently produced computer generated animation there is significant visual information that is literally never seen because of the characteristics of the human visual system. By tailoring the rendering of animation images to match the characteristics of human visual perception, significant computational and image storage savings can be obtained while retaining perceived animation quality. Vision research indicates that the human visual system processes two information channels. The transient channel rapidly processes low spatial resolution full colour information. The sustained channel processes high spatial resolution luminance information at a much slower rate. This paper discusses how the rendering of animation images can be accomplished to match these perception characteristics and achieve significant savings while maintaining animation quality. Computation and storage savings of up to 80 per cent are possible. Several animation segments have been produced to demonstrate the viability of this approach.     

Realistic animation of interactive trees

We present a mathematical model for animating trees realistically by taking into account the influence of natural frequencies and damping ratios. To create realistic motion of branches, we choose three basic mode shapes from the modal analysis of a curved beam, and combine them with a driven harmonic oscillator to approximate Lissajous curve which is observed in pull-and-release test of real trees. The forced vibration of trees is animated by utilizing local coordinate transformation before applying the forced vibration model of curved beams. In addition, we assume petioles are flexible to create natural motion of leaves. A wind field is generated by three-dimensional 1/f ^β noises to interact with the trees. Besides, our animation model allows users to interactively manipulate trees. We demonstrate several examples to show the realistic motion of interactive trees without using pre-computation or GPU acceleration. Various motions of trees can be achieved by choosing different combinations of natural frequencies and damping ratios according to tree species and seasons.     

Stylized highlights for cartoon rendering and animation

We propose a new highlight shader for the 3D objects used in cel animation. Without using a texture-mapping technique, our shader makes highlight shapes and animations in a cartoon style. Our shader makes an initial highlight shape using Blinn's (1977) traditional specular model. It then interactively modifies the initial shape through geometric, stylistic, and Boolean transformations for the highlight until we get our final desired shape. Moreover, once these operations specify highlight shapes for each keyframe, our shader automatically generates the highlight animation. In other words, our shader offers a new definition of highlighting 3D objects for cel animation.     

Realistic rendering with turbulent flows

This paper focuses on realistic rendering of scenes which include turbulent flows. In this respect we suggest solving the Navier–Stokes equations through a simple approach which offers better steadiness than classical methods. Then we adapt a ray‐tracing algorithm to treat convection motions by deflecting ray paths: we obtain effects of rendering through heat. Copyright © 2000 John Wiley & Sons, Ltd.     

三维地形场景的真实感绘制

三维地形场景的真实感绘制追求的两个目标是绘制的逼真度和绘制的实时性,需要在不明显降低图像质量的条件下保持较高的交互帧速率。为了满足实时性的需求,采用连续LOD算法和其它技术来加速地形绘制：为了满足逼真度的需求,采用SAR图像进行纹理映射,采用光照映射实现场景照明和明暗处理。     

A distributed rendering environment for teaching animation and scientific visualization

This article outlines the development of a DRE at Purdue University. Faculty and students are currently beta testing the DRE. The project's goal is to make DREs available to faculty and students throughout the US at no cost. The design addresses several pedagogical paradigms that are critical for enhanced positive learning outcomes. Critical to the development of Purdue's DRE is the notion of an enhanced positive user experience. To address this goal, the project team is focusing on engineering methods for one-touch job deployment; ease of job status monitoring; anywhere, anytime job submission; rendering and animation error correction; and reduced job wait times.     

Uncertainty visualization in medical volume rendering using probabilistic animation

Direct Volume Rendering has proved to be an effective visualization method for medical data sets and has reached wide-spread clinical use. The diagnostic exploration, in essence, corresponds to a tissue classification task, which is often complex and time-consuming. Moreover, a major problem is the lack of information on the uncertainty of the classification, which can have dramatic consequences for the diagnosis. In this paper this problem is addressed by proposing animation methods to convey uncertainty in the rendering. The foundation is a probabilistic Transfer Function model which allows for direct user interaction with the classification. The rendering is animated by sampling the probability domain over time, which results in varying appearance for uncertain regions. A particularly promising application of this technique is a "sensitivity lens" applied to focus regions in the data set. The methods have been evaluated by radiologists in a study simulating the clinical task of stenosis assessment, in which the animation technique is shown to outperform traditional rendering in terms of assessment accuracy.     

Physically-based modeling,simulation and rendering of fire for computer animation

We give an up-to-date survey on techniques and methods for fire simulation in computer graphics. Physically-based method prevails over traditional non-physical methods for realistic visual effect. In this paper, we explore visual simulation of fire-related phenomena in terms of physically modeling, numerical simulation and visual rendering. Firstly, we introduce a physical and chemical coupled mathematical model to explain fire behavior and motion. Several assumptions and constrains are put forward to simplify their implementations in computer graphics. We then give an overview of present methods to solve the most complicated processes in numerical simulation: velocity advection and pressure projection. In addition, comparisons of these methods are also presented respectively. Since fire is a participating medium as well as a visual radiator, we discuss techniques and problems of these issues as well. We conclude by addressing several open challenges and possible future research directions in fire simulation.     

R4: Realistic rain rendering in realtime

Realistic rain simulation is a challenging problem due to the variety of different phenomena to consider. In this paper we propose a new rain rendering algorithm that extends present state of the art in the field, achieving real-time rendering of rain streaks and splashes with complex illumination effects, along with fog, halos and light glows as hints of the participating media. Our algorithm creates particles in the scene using an artist-defined storm distribution (e.g., provided as a 2D cloud distribution). Unlike previous algorithms, no restrictions are imposed on the rain area dimension or shape. Our technique adaptively samples the storm area to simulate rain particles only in the relevant regions and only around the observer. Particle simulation is executed entirely in the graphics hardware, by placing the particles at their updated coordinates at each time-step, also checking for collisions with the scene. To render the rain streaks, we use precomputed images and combine them to achieve complex illumination effects. Several optimizations are introduced to render realistic rain with virtually millions of falling rain droplets.     

基于分形递归算法的树木真实感绘制

快速真实地模拟树在风中的摇曳一直是计算机图形学中的一个挑战性问题,作为自然场景的重要组成部分,树木的真实感模拟也得到人们的广泛重视.树木种类繁多,形态各异,复杂的结构使其无论在造形、存储还是在绘制上都存在着相当的困难.大多数园林设计软件很难构建模型参数可变的三维树.研究了一种简易的基于分形递归算法的建模方法,利用过程参数控制树的摇曳,使模型的真实感更强,变形计算更容易,得到了令人满意的实验效果.     

Realistic emotion visualization by combining facial animation and hairstyle synthesis

Facial expressions are one of most intuitive way for expressing emotions, and can facilitate human-computer interaction by enabling users to communicate with computers using more natural ways. Besides, the hair can be designed to enhance the expression of emotions particularly. To visualize the emotions in multiple aspects for completeness, we propose a realistic visual emotional synthesis system based on the combination of facial expression and hairstyle in this paper. Firstly, facial expression is synthesized by the anatomical model and parameterized model. Secondly, cartoonish hairstyle is synthesized to describe emotion implicitly by the mass-spring model and cantilever beam model. Finally, the synthesis results of facial expression and hairstyle are combined to produce a complete visual emotion synthesis result. Experiment results demonstrate the proposed system can synthesize realistic animation, and the emotion expressiveness by combining of face and hair outperform that by face or hair alone.     

Real-time feature-based image morphing for memory-efficient impostor rendering and animation on GPU

Real-time rendering of large animated crowds consisting of thousands of virtual humans is important for several applications including simulations, games, and interactive walkthroughs but cannot be performed using complex polygonal models at interactive frame rates. For that reason, methods using large numbers of precomputed image-based representations, called impostors, have been proposed. These methods take advantage of existing programmable graphics hardware to compensate for computational expense while maintaining visual fidelity. Thanks to these methods, the number of different virtual humans rendered in real time is no longer restricted by computational power but by texture memory consumed for the variety and discretization of their animations. This work proposes a resource-efficient impostor rendering methodology that employs image morphing techniques to reduce memory consumption while preserving perceptual quality, thus allowing higher diversity or resolution of the rendered crowds. Results of the experiments indicated that the proposed method, in comparison with conventional impostor rendering techniques, can obtain 38 % smoother animations or 87 % better appearance quality by reducing the number of key-frames required for preserving the animation quality via resynthesizing them with up to 92 % similarity on real time.     

MARS: A tool-based modeling,animation, and parallel rendering system

This paper describes a system for modeling, animating, previewing and rendering articulated objects. The system has a modeler of objects that consists of joints and segments. The animator interactively positions the articulated object in its stick, control vertex, or rectangular prism representation and previews the motion in real time. Then the data representing the motion and the models is sent to a multicomputer [iPSC/2 Hypercube (Intel)]. The frames are rendered in parallel, exploiting the coherence between successive frames, thus cutting down the rendering time significantly. Our main aim is to make a detailed study on rendering of a sequence of 3D scenes. The results show that due to an inherent correlation between the 3D scenes, an efficient rendering can be achieved.     

Realistic haptic rendering of interacting deformable objects in virtual environments

A new computer haptics algorithm to be used in general interactive manipulations of deformable virtual objects is presented. In multimodal interactive simulations, haptic feedback computation often comes from contact forces. Subsequently, the fidelity of haptic rendering depends significantly on contact space modeling. Contact and friction laws between deformable models are often simplified in up to date methods. They do not allow a "realistic" rendering of the subtleties of contact space physical phenomena (such as slip and stick effects due to friction or mechanical coupling between contacts). In this paper, we use Signorini's contact law and Coulomb's friction law as a computer haptics basis. Real-time performance is made possible thanks to a linearization of the behavior in the contact space, formulated as the so-called Delassus operator, and iteratively solved by a Gauss-Seidel type algorithm. Dynamic deformation uses corotational global formulation to obtain the Delassus operator in which the mass and stiffness ratio are dissociated from the simulation time step. This last point is crucial to keep stable haptic feedback. This global approach has been packaged, implemented, and tested. Stable and realistic 6D haptic feedback is demonstrated through a clipping task experiment.     

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.     

Realistic rendering of an organ surface in real-time for laparoscopic surgery simulation

Published online: 23 April 2002     

Modeling and visualization of knitwear

Visualization and modeling of textile materials has already been investigated in detail in the computer graphics literature. Most of the work, however, concentrates on woven fabrics. We present a novel approach to the modeling and rendering of knitwear. After the topological specification of a knitting pattern a subdivision into basic elements is done. The yarn microstructure within basic elements is approximated by volume data sets. The repetitive structure of knitted fabrics allows an efficient rendering technique. Resulting images are given that demonstrate the feasibility of our approach