Fast Phong明暗处理算法的FPGA实现

Phong明暗处理算法是生成真实感3D图像的最佳算法之一。VLSI技术的发展以及对于高真实感实时图形的需求使得Phong明暗处理算法的实现成为可能。利用泰勒级数近似的Fast Phong明暗处理算法适合硬件实现。但是用硬件实现此算法需要存储大量数据的ROM表,这增加了实现的难度。通过误差分析,提出了优化的查找表结构。通过在FPGA上对所提结构进行验证,结果表明,该方案在提高速度、精度的同时减小了硬件资源的使用量。     

基于shader实现的光线透射效果

真实的模拟光线的透射效果是实时计算机图形学中一个非常令人关注的内容.对于这种自然现象的模拟所要达到的两个目标是真实性和实时性.为了达到这一要求,介绍了一种能够实时并且真实的模拟这种自然现象的算法,在Microsoft Visual Studio开发环境下,利用DirectX9.0软件包进行3D开发,并结合shader技术编程实现,运行的结果表明此算法是可行的和高效的.     

Solving aliasing from shading with selective shader supersampling

Existing GPU antialiasing techniques, such as MSAA or MLAA, focus on reducing aliasing artifacts along silhouette boundaries or edges in image space. However, they neglect aliasing from shading in case of high-frequency geometric detail. This may lead to a shading aliasing artifact that resembles Bailey's Bead Phenomenon—the degradation of continuous specular highlights to a string of pearls. These types of artifacts are particularly striking for high-quality surfaces. So far, the only way of removing aliasing from shading is by globally supersampling the entire image with a large number of samples. However, globally supersampling the image is slow and significantly increases bandwidth consumption. We propose three adaptive approaches that locally supersample triangles only where necessary on the GPU. Thereby, we efficiently remove artifacts from shading while aliasing along silhouettes is reduced by efficient hardware MSAA.     

面向移动设备的可编程像素渲染器的设计

传统的图形处理器中的像素混合单元是用功能固定的电路来实现的,实现了一个高性能的面向移动设备的可编程像素渲染器的设计。该处理器采用定点数操作,实现了4路共128位的单指令多数据的运算单元和具备数据旁路功能的8级流水线。这些结构特性有效地减少了电路面积,提高了像素渲染器的运算速度。该像素渲染器在FPGA平台上的实验结果表明,用户可以通过编程实现自定义的像素混合算法,以渲染出各种不同的特殊效果。     

Social evaluations of embodied agents and avatars

The purpose of this study was to examine social evaluations (i.e., perceptions of empathy and positivity) following peoples’ interactions with digital human representations. Female research participants engaged in a 3-min interaction while immersed in a 3-D immersive virtual environment with a “peer counselor.” Participants were led to believe that the peer counselor was either an embodied agent (i.e., computer algorithm) or an avatar (i.e., another person). During the interaction, the peer counselor either smiled or not. As predicted, a digitally-rendered smile was found to affect participants’ social evaluations. However, these effects were moderated by participants’ beliefs about their interaction partner. Specifically, smiles enhanced social evaluations of embodied agents but degraded them for avatars. Although these results are consistent with other findings concerning the communicative realism of embodied agents and avatars they uniquely demonstrate that people’s beliefs alone, rather than actual differences in virtual representations, can impact social evaluations.     

Parametric editing of clothed 3D avatars

Easy editing of a clothed 3D human avatar is central to many practical applications. However, it is easy to produce implausible, unnatural looking results, since subtle reshaping or pose alteration of avatars requires global consistency and agreement with human anatomy. Here, we present a parametric editing system for a clothed human body, based on use of a revised SCAPE model. We show that the parameters of the model can be estimated directly from a clothed avatar, and that it can be used as a basis for realistic, real-time editing of the clothed avatar mesh via a novel 3D body-aware warping scheme. The avatar can be easily controlled by a few semantically meaningful parameters, 12 biometric attributes controlling body shape, and 17 bones controlling pose. Our experiments demonstrate that our system can interactively produce visually pleasing results.     

Dynamic shader generation for GPU-based multi-volume ray casting

Real-time performance for rendering multiple intersecting volumetric objects requires the speed and flexibility of modern GPUs. This requirement has restricted programming of the necessary shaders to GPU experts only. A visualization system that dynamically generates GPU shaders for multi-volume ray casting from a user-definable abstract render graph overcomes this limitation.     

A flexible multi-volume shader framework for arbitrarily intersecting multi-resolution datasets

We present a powerful framework for 3D-texture-based rendering of multiple arbitrarily intersecting volumetric datasets. Each volume is represented by a multi-resolution octree-based structure and we use out-of-core techniques to support extremely large volumes. Users define a set of convex polyhedral volume lenses, which may be associated with one or more volumetric datasets. The volumes or the lenses can be interactively moved around while the region inside each lens is rendered using interactively defined multi-volume shaders. Our rendering pipeline splits each lens into multiple convex regions such that each region is homogenous and contains a fixed number of volumes. Each such region is further split by the brick boundaries of the associated octree representations. The resulting puzzle of lens fragments is sorted in front-to-back or back-to-front order using a combination of a view-dependent octree traversal and a GPU-based depth peeling technique. Our current implementation uses slice-based volume rendering and allows interactive roaming through multiple intersecting multi-gigabyte volumes.     

Signing avatars: making education more inclusive

Universal Access in the Information Society - In Brazil, there are approximately 9.7 million inhabitants who are deaf or hard of hearing. Moreover, about 30% of the Brazilian deaf community is...     

Efficient multi-view ray tracing using edge detection and shader reuse

Stereoscopic rendering and 3D stereo displays are quickly becoming mainstream. The natural extension is autostereoscopic multi-view displays which, by the use of parallax barriers or lenticular lenses, can accommodate many simultaneous viewers without the need for active or passive glasses. As these displays, for the foreseeable future, will support only a rather limited number of views, there is a need for high-quality interperspective antialiasing. We present a specialized algorithm for efficient multi-view image generation from a camera line using ray tracing, which builds on previous methods for multi-dimensional adaptive sampling and reconstruction of light fields. We introduce multi-view silhouette edges to detect sharp geometrical discontinuities in the radiance function. These are used to significantly improve the quality of the reconstruction. In addition, we exploit shader coherence by computing analytical visibility between shading points and the camera line, and by sharing shading computations over the camera line.     

The avatars of a package for calendars in ada

This paper shows the evolution of components for calendars written in Ada, starting from a classic form and evolving by the effect of some choices of software engineering. The first choice is to specify separate components when they do not have to be coupled in only one. This choice transforms a one-component form into a three-component one. The second choice is to hide all entities that are not required by the modelling of the real world. This choice modifies many declarations into forms which are complex to specify but which introduce no additional complexity to the user. In addition to the development of this component for the current legal calendar, it is indicated how others can be defined and converted from any one to the other. The design of a deep automatic test is illustrated. Finally, the paper illustrates how the new features of Ada-95 can be used to specify these calendars in another form, but which is not essentially different from the Ada-83 text.     

An instruction-systolic programmable shader architecture for multi-threaded 3D graphics processing

In order to guarantee both performance and programmability demands in 3D graphics applications, vector and multithreaded SIMD architectures have been employed in recent graphics processing units. This paper introduces a novel instruction-systolic array architecture, which transfers an instruction stream in a pipelined fashion to efficiently share the expensive functional resources of a graphics processor. Specifically, cache misses and dynamic branches can cause additional latencies and complicated management in these parallel architectures. To address this problem, we combine a systolic execution scheme with on-demand warp activation that handles cache miss latency and branch divergence efficiently without significantly increasing hardware resources, either in terms of logic or register space. Simulation indicates that the proposed architecture offers 25% better performance than a traditional SIMD architecture with the same resources, and requires significantly fewer resources to match the performance of a typical modern vector multi-threaded GPU architecture.     

UHP lamps for projection

UHP lamps are now standard equipment in highly efficient projection systems. These systems are moving toward smaller displays, brighter screens, and ultra‐compactness. Consequently, a range of UHP lamps has been developed to fulfil these ever‐increasing demands. This paper describes the basic principles of UHP lamps and reviews the major achievements made over the last several years, which include reduction in arc size, arc stabilization, and ignition voltage reduction.     

Anti-smoking educational game using avatars as visualized possible selves

Few social smokers envision themselves being affected by the negative consequences of smoking despite well-known facts that smoking causes serious illnesses and death. However, as smoking habits quickly develop, social smokers cannot be free from the negative consequences of smoking. In this study, we pose the following question: “Would showing social smokers’ possible future as a consequence of smoking help them alter their current smoking behaviors?” Thus, using the theoretical concept of possible selves, an anti-smoking educational game was created in which players could see changes to the appearance of their future selves as a consequence of smoking. We used a 2 (Future face: Showing vs. Not showing) × 2 (Self avatar: Self-avatar vs. Other-avatar) between-subjects design for the experiment. Results indicated that participants who viewed the future face, compared to who did not, reported more negative attitudes toward social smoking and greater intention to quit smoking. The main effect of the self avatar was insignificant; however, seeing the future face in the self-avatar condition led to an increase in perceived risks compared to other-avatar condition. The implications of using avatars as visualized possible selves in health promotion are discussed.     

Using avatars to tailor ideation process to innovation strategy

To face innovation challenges of the twenty-first century, companies should learn from proven successful strategies and draw on technological evolutions as well. Our proposal consists in aligning ideation to innovation strategies through the use of avatars in a virtual world. On the basis of the Persona method and the Proteus effect, we design avatars’ appearance so as to implement a Need-seeker or a Technology-driver innovation strategy. To test the effectiveness of this avatar-mediated innovation tool, we conducted an experiment in a French company. Two groups of highly qualified employees from the innovation department had to find applications for smart windows in public transportation. Both groups experienced immersion in a virtual transportation situation: one group embodied avatars resembling Inventors, whereas the other group embodied Personas representing users of public transportation. As expected, avatars’ appearance proved to influence the creative production: the Inventor condition led to a techno-centered ideation profile, oriented toward technological solutions, while the Persona condition led to more user-centered, needs-oriented ideas. Consistently, Inventors’ production tended to be better evaluated through industrial criteria and Personas’ production tended to be better evaluated by transportation users. We discuss the use of avatar-mediated creativity as a strategic tool for companies seeking to innovate.     

Cross-modal compensation between name and visual aspect in socially active avatars

Avatars serve for humans immersed in virtual settings as the interface between real and virtual worlds. The avatar-creation process involves numerous choices, including choice of visual representation, and choices to imbue the character with personality. Here, we hypothesised that these choices are not independent, and that a cross-modal talk may occur between the different components of the avatar identity. Specifically, we investigated whether name properties may be affected by the visual aspect (human vs. non-human) of the avatar. We analyzed names structure of players characters from the popular massively multiplayer online role-playing game (MMORPG) World of Warcraft, which display both human and non-human avatars. We selected 1261 names of characters actively engaged in the in-game and out-game social networks. Analysis of the names revealed that female names presented more variability than male names, and contained systematically more vowels than male names. However, the strategy used to enrich the vowel composition of female names differed between human-like and non-human characters, suggesting that a lesser proximity with human regular appearance was compensated by an increase of “feminization” of the name. Altogether, our results suggest that a cross-modal compensation occurs between name and visual aspect in the creation of socially active avatars.     

Cognitive and synthetic behavior of avatars in intelligent virtual environments

In intelligent virtual environments (IVEs), it is a challenging research issue to provide the intelligent virtual actors (or avatars) with the ability of visual perception and rapid response to virtual world events. Modeling an avatar’s cognitive and synthetic behavior appropriately is of paramount important in IVEs. We propose a new cognitive and behavior modeling methodology that integrates two previously developed complementary approaches. We present expression cloning, walking synthetic behavior modeling, and an autonomous agent cognitive model for driving an avatar’s behavior. Facial expressions are generated using our own-developed rule-based state transition system. Facial expressions are further personalized for individuals by expression cloning. An avatar’s walking behavior is modeled using a skeleton model that is implemented by seven-motion sequences and finite state machines (FSMs). We discuss experimental results demonstrating the benefits of our approach.     

On generating realistic avatars: dress in your own style

The use of 3D avatars is becoming more frequent with the development of computer technology and the internet. To meet users?? requirements, some software or programs have allowed users to customize the avatar. However, users are only able to customize the avatar using the pre-defined accessories such as hair, clothing and so on. That is, users have limited chance to customize the avatar according to their own styles. It will be of interest to users if they are able to change the appearance of the avatar by their own design, such as creating garments for avatars themselves. This paper provides an easy solution to dressing realistic 3D avatars for non-professional users based on a sketch interface. After a user drawing a 2D garment profile around the avatar, the prototype system can generate an elaborate 3D geometric garment surface dressed on the avatar. The construction of the garment surface is constrained by key body features. And the garment shape is then optimized to remove artefacts. The proposed method can generate a uniform mesh for processing such as mesh refinement, 3D decoration and so on.     

Public speaking in virtual reality: facing an audience of avatars

What happens when someone talks in public to an audience they know to be entirely computer generated-to an audience of avatars? If the virtual audience seems attentive, well-behaved, and interested, if they show positive facial expressions with complimentary actions such as clapping and nodding, does the speaker infer correspondingly positive evaluations of performance and show fewer signs of anxiety? On the other hand, if the audience seems hostile, disinterested, and visibly bored, if they have negative facial expressions and exhibit reactions such as head-shaking, loud yawning, turning away, falling asleep, and walking out, does the speaker infer correspondingly negative evaluations of performance and show more signs of anxiety? We set out to study this question during the summer of 1998. We designed a virtual public speaking scenario, followed by an experimental study. We wanted mainly to explore the effectiveness of virtual environments (VEs) in psychotherapy for social phobias. Rather than plunge straight in and design a virtual reality therapy tool, we first tackled the question of whether real people's emotional responses are appropriate to the behavior of the virtual people with whom they may interact. The project used DIVE (Distributive Interactive Virtual Environment) as the basis for constructing a working prototype of a virtual public speaking simulation. We constructed as a Virtual Reality Modeling Language (VRML) model, a virtual seminar room that matched the actual seminar room in which subjects completed their various questionnaires and met with the experimenters     

Program-based dynamic precision selection framework with a dual-mode unified shader for mobile GPUs

To extend the life of battery-driven mobile devices while maintaining image quality, this work proposes a Program-based Dynamic Precision Selection (PDPS) framework with a dual-mode unified shader. Since fixed-point arithmetic can be performed faster and more energy-efficiently than floating-point arithmetic on power-limited devices, the use of fixed-point rather than floating-point rendering is a critical concern. The proposed PDPS framework is composed of a runtime profile-based mechanism for automatically determining the precision of each shading program in fixed-point arithmetic. Additionally, a scene change detection mechanism is developed to recalculate the rendering precision whenever a 3D scene changes. The results reveal an average 18% reduction in energy and 35% faster performance under fixed-point rendering. The degradation in rendered image quality under the proposed PDPS cannot be detected by the naked eye, and the PSNR is an average of 15% better than that achieved using related approach.