Haptic rendering for dental training system

Immersion and interaction are two key features of virtual reality systems, which are especially important for medical applications. Based on the requirement of motor skill training in dental surgery, haptic rendering method based on triangle model is investigated in this paper. Multi-rate haptic rendering architecture is proposed to solve the contradiction between fidelity and efficiency requirements. Realtime collision detection algorithm based on spatial partition and time coherence is utilized to enable fast contact determination. Proxy-based collision response algorithm is proposed to compute surface contact point. Cutting force model based on piecewise contact transition model is proposed for dental drilling simulation during tooth preparation. Velocity-driven levels of detail haptic rendering algorithm is proposed to maintain high update rate for complex scenes with a large number of triangles. Hapticvisual collocated dental training prototype is established using half-mirror solution. Typical dental operations have been realized including dental caries exploration, detection of boundary within dental cross-section plane, and dental drilling during tooth preparation. The haptic rendering method is a fundamental technology to improve immersion and interaction of virtual reality training systems, which is useful not only in dental training, but also in other surgical training systems. Supported by National Natural Science Foundation of China (Grant Nos. 60605027, 50575011), National High-Tech Research & Development Program of China (Grant No. 2007AA01Z310)     

Interactive visualization of medical volume models in mobile devices

Interactive visualization of volume models in standard mobile devices is a challenging present problem with increasing interest from new application fields like telemedicine. The complexity of present volume models in medical applications is continuously increasing, therefore increasing the gap between the available models and the rendering capabilities in low-end mobile clients. New and efficient rendering algorithms and interaction paradigms are required for these small platforms. In this paper, we propose a transfer function-aware compression and interaction scheme, for client-server architectures with visualization on standard mobile devices. The scheme is block-based, supporting adaptive ray-casting in the client. Our two-level ray-casting allows focusing on small details on targeted regions while keeping bounded memory requirements in the GPU of the client. Our approach includes a transfer function-aware compression scheme based on a local wavelet transformation, together with a bricking scheme that supports interactive inspection and levels of detail in the mobile device client. We also use a quantization technique that takes into account a perceptive metrics of the visual error. Our results show that we can have full interaction with high compression rates and with transmitted model sizes that can be of the order of a single photographic image.     

Feature lines extraction for remote rendering on point model

In this paper, we propose a method to extract feature lines on point model via an implicit fitting process at various scales. Based on these feature lines, we present a feature-based remote rendering scheme to interactively display large-scale point models on mobile devices over a low-bandwidth wireless network. By quickly loading and rendering the feature-line representations, users can well capture the general shape and main features of a model. Further a hybrid rendering of point and feature line helps to interactively display regions of interest. If with a powerful rendering capability, clients can also approximately reconstruct the model guided by the features. Experiments show that a small amount of feature lines can hold the ruling perceptual details and deliver a good visual impression.     

IETF softwire unicast and multicast framework for IPv6 transition

IPv6 protocol plays an important role in the next generation of Internet （NGI）. It is expected that the elegant coexistence of IPv4 and IPv6 is the key point of IPv6 transition. To solve the transition problem, we propose a mesh unicast framework and a multicast framework in this paper. We describe two reference models for the mesh unicast framework, and put forward two potential solutions for the multicast framework. A Linux-based prototype is implemented for IPv4 over IPv6 scenario and a test bed is deployed with 8 nodes on CERNET2. The deployment demon- strates the advantages of the framework.     

ASEHM: a new transmission control mechanism for remote rendering system

Digital 3D models have emerged as a new type of multimedia following sound, image and video. This media type has been distributed and processed widely on desktop PCs. However, processing 3D models on mobile devices is more difficult, mainly due to their physical constraints. Though the remote rendering framework is able to make up for some deficiencies, previous methods based on this framework suffered from high transmission frequency, which just imposes a high power demand on mobile devices’ already limited battery life. In this paper, a new transmission control method, Adaptive Splitting and Error Handling Mechanism, is proposed to be integrated with canonical remote rendering system. Our mechanism is able to reduce transmission frequency by trading transmission with splitting operations. According to relevant research findings, reducing frequency will result in a decline in power consumption. Finally, the effectiveness of our method in terms of frequency reduction is validated by comparison with state of the art method.     

A framework for remote rendering of 3-D scenes on limited mobile devices

This paper describes a networked three-dimensional (3-D) rendering framework that allows low-powered mobile devices to simulate the interactive rendering of remote dense 3-D environment. The framework is based on 3-D image warping, especially suited to low-resolution screens and involves the transmission of sparse residual images. The use of an oversized reference image, superview, to cope with the visibility gap errors and the acceleration techniques aimed at improving the frame-rates are explored. It is shown that the described framework offers a potential alternative for interactive rendering of remote 3-D environment on low-powered clients where the triangle mesh display is impractical.     

Demand-Driven Memory Leak Detection Based on Flow- and Context-Sensitive Pointer Analysis

We present a demand-driven approach to memory leak detection algorithm based on flow- and context-sensitive pointer analysis. The detection algorithm firstly assumes the presence of a memory leak at some program point and then runs a backward analysis to see if this assumption can be disproved. Our algorithm computes the memory abstraction of programs based on points-to graph resulting from flow- and context-sensitive pointer analysis. We have implemented the algorithm in the SUIF2 compiler infrastructure and used the implementation to analyze a set of C benchmark programs. The experimental results show that the approach has better precision with satisfied scalability as expected. This work is supported by the National Natural Science Foundation of China under Grant Nos. 60725206, 60673118, and 90612009, the National High-Tech Research and Development 863 Program of China under Grant No. 2006AA01Z429, the National Basic Research 973 Program of China under Grant No. 2005CB321802, the Program for New Century Excellent Talents in University under Grant No. NCET-04-0996, and the Hunan Natural Science Foundation under Grant No. 07JJ1011.     

Lumiproxy: A Hybrid Representation of Image-Based Models

In this paper,we present a hybrid representation of image-based models combining the textured planes and the hierarchical points.Taking a set of depth images as input,our method starts from classifying input pixels into two categories,indicating the planar and non-planar surfaces respectively.For the planar surfaces,the geometric coefficients are reconstructed to form the uniformly sampled textures.For nearly planar surfaces,some textured planes,called lumiproxies, are constructed to represent the equiva...     

Clustered Chain Path Index for XML Document: Efficiently Processing Branch Queries

Branch query processing is a core operation of XML query processing. In recent years, a number of stack based twig join algorithms have been proposed to process twig queries based on tag stream index. However, in tag stream index, each element is labeled separately without considering the similarity among elements. Besides, algorithms based on tag stream index perform inefficiently on large document. This paper proposes a novel index, named Clustered Chain Path Index, based on a novel labeling scheme. This index provides efficient support for processing branch queries. It also has the same cardinality as 1-index against tree structured XML document. Based on CCPI, efficient algorithms, KMP-Match-Path and Related-Path-Segment-Join, are proposed to process queries efficiently. Analysis and experimental results show that proposed query processing algorithms based on CCPI outperform other algorithms and have good scalability. This paper is partially supported by Natural Science Foundation of Heilongjiang Province, Grant No. zjg03-05 and National Natural Science Foundation of China, Grant No. 60473075 and Key Program of the National Natural Science Foundation of China, Grant No. 60533110.     

Multiresolution and fast decompression for optimal web-based rendering

Limited bandwidth is a strong constraint when efficient transmission of 3D data to Web clients and mobile applications is needed. In this paper we present a novel multi-resolution WebGL based rendering algorithm which combines progressive loading, view-dependent resolution and mesh compression, providing high frame rates and a decoding speed of million of triangles per second in JavaScript. The method is parallelizable and scalable to very large models.The algorithm is based on the local multi-resolution approaches provided by the community, but ad-hoc solutions had to be studied and implemented to provide adequate performances. In particular, a compression mechanism that reached very high compression rate without impact on rendering performance was implemented. Moreover, the data partition strategy was modified in order to be able to load different types of data (i.e. point clouds) and better adapt to the potentials and limitations of web-based rendering.     

保留细节特征的轮廓线远程绘制算法

目前,智能掌上电脑、个人数字助理和智能手机等移动终端因为其便携性和可移动性,越来越多地被应用于分布式虚拟环境中,但是因为移动终端自身的局限性,在移动终端上的3维模型实时绘制问题仍未得到很好的解决。结合多分辨率网格模型和基于轮廓线的远程绘制的优点,提出了一种保留细节特征的轮廓线远程绘制算法。该算法预处理阶段,在原始精细网格模型上提取细节特征线,并进行多分辨率网格模型的预处理;运行时阶段,根据视点、帧率等交互信息使用选取策略对细节特征线进行选取,然后构建合适的多分辨率网格模型,并在该模型上提取出外围轮廓线,最后发送这两种轮廓线到移动终端进行绘制。实验结果表明,该算法在基于轮廓线的远程绘制中较好地保留了模型的细节特征,并保证了在移动终端的实时绘制。     

Asymmetric and selective object rendering for optimized Cloud Mobile 3D Display Gaming user experience

Cloud Mobile 3D Display Gaming has been recently proposed where 3D video rendering and encoding are performed on cloud servers, with the resulting 3D video streamed wirelessly to mobile devices with 3D displays. This approach has the advantage of relieving high computation, power and storage requirements of 3D display gaming from mobile devices, while enabling game developers to focus on a single rich version of the game which can be experienced from any mobile device and platform. However, it is challenging to stream 3D video over dynamically fluctuating and often constrained mobile networks. In this paper, we propose a novel technique called Asymmetric and Selective Object Rendering (ASOR) which proves to be more powerful than previous solutions for Cloud based Mobile 3D display gaming. Specifically, this technique will enable rendering engine to intelligently decide whether or not to render an individual object and how good the corresponding texture detail will be if rendered, and the settings can be asymmetric for two views. Thus, unimportant objects can trade quality for reduced bitrate while important objects can remain high quality so that the overall user experience is optimized given certain bandwidth constraints. To quantitatively measure the user experience and bitrate by applying different rendering settings, we develop a user experience model and a bitrate model. We further propose an optimization algorithm which uses the above two models to automatically decide the optimal rendering settings for left view and right view to ensure the best user experience given the network conditions. Experiments conducted using real 4G-LTE network profiles on commercial cloud service with different genres of games demonstrate significant improvement in user experience when the proposed optimization algorithm is applied.     

Super-resolution image reconstruction for mobile devices

With advanced mobile devices, the mobile applications of the high-definition display attract a lot of attentions nowadays. The existing image super-resolution methods are computationally inefficient for the high-definition display on the mobile devices. In this paper, we point out that the above critical issue deteriorates the display quality of the high-definition mobile devices. We propose an efficient and effective algorithm to reconstruct the high-resolution images for the mobile devices. Our algorithm outperforms previous approaches in not only smaller running time but also the higher quality of the super-resolution image reconstruction for the mobile devices.     

A mobile crowd sensing ecosystem enabled by CUPUS: Cloud-based publish/subscribe middleware for the Internet of Things

Mobile crowd sensing (MCS) is a novel class of mobile Internet of Things (IoT) applications for community sensing where sensors and mobile devices jointly collect and share data of interest to observe phenomena over a large geographic area. The inherent device mobility and high sensing frequency has the capacity to produce dense and rich spatiotemporal information about our environment, but also creates new challenges due to device dynamicity and energy constraints, as well as large volumes of generated raw sensor data which need to be processed and analyzed to extract useful information for end users. The paper presents an ecosystem for mobile crowd sensing which relies on the CloUd-based PUblish/Subscribe middleware (CUPUS) to acquire sensor data from mobile devices in a flexible and energy-efficient manner and to perform near real-time processing of Big Data streams. CUPUS has unique features compared to other MCS platforms: It enables management of mobile sensor resources within the cloud, supports filtering and aggregation of sensor data on mobile devices prior to its transmission into the cloud based on global data requirements, and can push information of interest from the cloud to user devices in near real-time. We present our experience with implementation and deployment of an MCS application for air quality monitoring built on top of the CUPUS middleware. Our experimental evaluation shows that CUPUS offers scalable processing performance, both on mobile devices and within the cloud, while its data propagation delay is mainly affected by transmission delay on wireless links.     

移动设备上基于三维模型的线条画绘制

提出一种综合考虑移动设备客户端绘制能力和传输速度的混合型远程绘制方法.该方法采用渐进网格得到不同分辨率的细节层次模型,并利用渐进传输机制逐步传输数据,以缓解单次网络负载.服务器端可以根据网络质量状况、移动客户端的处理能力和用户交互请求来选择适宜的三维细节层次模型,提取特征轮廓线并将生成的线条集合传输给客户端进行本地风格化绘制.将该方法应用于考古数字博物馆展示中取得了良好的效果.     

Interactive Illustrative Rendering on Mobile Devices

Scientists, engineers, and artists regularly use illustrations in design, training, and education to display conceptual information, describe problems, and solve those problems. Researchers have developed many advanced rendering techniques on desktop platforms to facilitate illustration generation, but adapting these techniques to mobile platforms has not been easy. We discuss how advanced illustrative rendering techniques, such as interactive cutaway views, ghosted views, silhouettes, and selective rendering, have been adapted to mobile devices. We also present MobileVis, our interactive, illustrative 3D graphics and text rendering system that lets users explore 3D models' interior structures, display parts annotations, and visualize instructions, such as assembly and disassembly procedures for mechanical models     

手机广告推荐中的用户兴趣建模研究*

为了增强基于WAP网页的手机广告推荐中用户建模的准确性,并对"非邀"式广告推荐中脱离用户兴趣试探性推荐进行修正,针对手机广告推荐中手机屏幕小、用户注意力集中等特点,根据用户对广告的访问历史和操作模式建立其广告兴趣模型和非兴趣模型,同时分析用户网页访问模式探测其网页兴趣度,在此基础上建立用户综合兴趣模型。分别采用基于网页兴趣模型、基于广告兴趣模型和基于用户综合兴趣模型进行广告推荐,随着样本空间增大,综合兴趣模型的查准率明显优于另两者。实验验证了用户综合兴趣模型在手机广告推荐中的有效性和优越性。     

LoI: Efficient relevance evaluation and filtering for distributed simulation

In large-scale distributed simulation, thousands of objects keep moving and interacting in a virtual environment, which produces a mass of messages. High level architecture (HLA) is the prevailing standard for modeling and simulation. It specifies two publish-subscribe mechanisms for message filtering: class-based and value-based. However, the two mechanisms can only judge whether a message is relevant to a subscriber or not. Lacking of the ability to evaluate the relevance, all relevant messages are delivered with the same priority even when congestion occurs. It significantly limits the scalability and performance of distributed simulation. Aiming to solve the relevance evaluation problem, speed up message filtering, and filter more unnecessary messages, a new relevance evaluation mechanism Layer of Interest (LoI) was proposed by this paper. LoI defines a relevance classifier based on the impact of spatial distance on receiving attributes and attribute values. An adaptive publish-subscribe scheme was built on the basis of LoI. This scheme can abandon most irrelevant messages directly. Run-time infrastructure (RTI) can also apply congestion control by reducing the frequency of sending or receiving object messages based on each objects’ LoI. The experiment results verify the efficiency of message filtering and RTI congestion control. Supported by the National Basic Research Program of China (Grant No. 2009CB320805), the National Natural Science Foundation of China (Grant No. 60603084), and the National High-Tech Research & Development Program of China (Grant No. 2006AA01Z331)     

CAD data visualization on mobile devices using sequential constrained Delaunay triangulation

3D graphic rendering in mobile application programs is becoming increasingly popular with rapid advances in mobile device technology. Current 3D graphic rendering engines for mobile devices do not provide triangulation capabilities for surfaces; therefore, mobile 3D graphic applications have been dealing only with pre-tessellated geometric data. Since triangulation is comparatively expensive in terms of computation, real-time tessellation cannot be easily implemented on mobile devices with limited resources. No research has yet been reported on real-time triangulation on mobile devices.In this paper, we propose a real-time triangulation algorithm for visualization on mobile devices based on sequential constrained Delaunay triangulation. We apply a compact data structure and a sequential triangulation process for visualization of CAD data on mobile devices. In order to achieve a high performance and compact implementation of the triangulation, the nature of the CAD data is fully considered in the computational process. This paper also presents a prototype implementation for a mobile 3D CAD viewer running on a handheld Personal Digital Assistant (PDA).     

Runtime Monitoring CompositeWeb Services Through Stateful Aspect Extension

The execution of composite Web services with WS-BPEL relies on externally autonomous Web services. This implies the need to constantly monitor the running behavior of the involved parties. Moreover, monitoring the execution of composite Web services for particular patterns is critical to enhance the reliability of the processes. In this paper, we propose an aspect-oriented framework as a solution to provide monitoring and recovery support for composite Web services. In particular, this framework includes 1) a stateful aspect based template, where history-based pointcut specifies patterns of interest cannot be violated within a range, while advice specifies the associated recovery action; 2) a tool support for runtime monitoring and recovery based on aspect-oriented execution environment. Our experiments indicate that the proposed monitoring approach incurs minimal overhead and is efficient. This work is supported by the National Natural Science Foundation of China under Grant Nos. 60673112, 90718033, the National Basic Research 973 Program of China under Grant No. 2009CB320704, and the High-Tech Research and Development 863 Program of China under Grand Nos. 2006AA01Z19B, 2007AA010301.