2365659
A Trajectory-Preserving Synchronization Method for Collaborative Visualization
In the past decade, a lot of research work has been conducted to support collaborative visualization among remote users over the networks, allowing them to visualize and manipulate shared data for problem solving. There are many applications of collaborative visualization, such as oceanography, meteorology and medical science. To facilitate user interaction, a critical system requirement for collaborative visualization is to ensure that remote users would perceive a synchronized view of the shared data. Failing this requirement, the user's ability in performing the desirable collaborative tasks would be affected. In this paper, we propose a synchronization method to support collaborative visualization. It considers how interaction with dynamic objects is perceived by application participants under the existence of network latency, and remedies the motion trajectory of the dynamic objects. It also handles the false positive and false negative collision detection problems. The new method is particularly well designed for handling content changes due to unpredictable user interventions or object collisions. We demonstrate the effectiveness of our method through a number of experiments
16124997
GameOD: an internet based game-on-demand framework
Multiplayer online 3D games are becoming very popular in recent years. However, existing games require the complete game content to be installed prior to game playing. Since the content is usually large in size, it may be difficult to run these games on a PDA or other handheld devices. It also pushes game companies to distribute their games as CDROMs/DVDROMs rather than online downloading. On the other hand, due to network latency, players may perceive discrepant status of some dynamic game objects. In this paper, we present a game-on-demand (GameOD) framework to distribute game content progressively in an on-demand manner. It allows critical contents to be available at the players' machines in a timely fashion. We present a simple distributed synchronization method to allow concurrent players to synchronize their perceived game status. Finally, we show some performance results of the proposed framework.
9839431
VSculpt : a distributed virtual sculpting environment for collaborative design
A collaborative virtual sculpting system supports a team of geographically separated designers/engineers connected by networks to participate in designing three-dimensional (3D) virtual engineering tools or sculptures. It encourages international collaboration at a minimal cost. However, in order for the system to be useful, two factors need to be addressed: intuitiveness and real-time interaction. Although a lot of effort has been put into developing virtual sculpting environments, only limited work addresses collaborative virtual sculpting. This is because in order to support real-time collaborative virtual sculpting, many challenging issues need to be addressed. We propose a collaborative virtual sculpting framework, called VSculpt. Through adapting some techniques we developed earlier and integrating them with some techniques developed here, the proposed framework provides a real-time intuitive environment for collaborative design. In particular, it addresses issues on efficient rendering and transmission of deformable objects, intuitive object deformation using the CyberGlove and concurrent object deformation by multiple clients. We demonstrate and evaluate the performance of the proposed framework through a number of experiments.
14580455
Supporting continuous consistency in multiplayer online games
Multiplayer online games have become very popular in recent years. However, they generally suffer from network latency problem. If a player changes its states, it will take some time before the changes are reflected to other concurrent players. This significantly affects the interactivity of the game. Sometimes, it may even cause disputes among the players. In this paper, we present a continuous consistency control mechanism to support collaborative game applications. Specifically, we propose a relaxed consistency control model for continuous events. Based on this model, we have developed a method to provide a global-wise continuous synchronization on the states of dynamic game objects presented among concurrent game players. We show the performance of the proposed method through some experiments.
14081654
Real-time rendering of deformable parametric free-form surfaces
Deformable objects are required to improve the realism of virtual reality applications. They are particularly useful in modeling clothes, facial expression, human and animal characters. A common method to render these objects is by tessellation. However, the tessellation process is computationally very expensive. If the object deforms, we need to retessellate the surface every frame, as its shape changes from one frame to the next. This computational burden poses a significant challenge to the real-time rendering of deformable objects. Consequently, deformable objects are seldom incorporated in existing virtual reality systems. In this paper, we present an incremental method for rendering deformable objects modeled by parametric free-form surfaces. We also introduce two new frame coherence techniques for crack prevention and parameter caching. Finally, we present a single hierarchical data structure which provides a multi-resolution representation of the object model.
41742727
Efficient rendering of deformable objects for real-time applications
Deformable objects can be used to model soft objects such as clothing, human faces and animal characters. They are important as they can improve the realism of the applications. However, most existing hardware accelerators cannot render deformable objects directly. A tessellation process is often used to convert a deformable object into polygons so that the hardware graphics accelerator may render them. Unfortunately, this tessellation process is computationally very expensive. While the object is deforming, the tessellation process needs to be performed repeatedly to convert the deforming objects into polygons. As a result, deformable objects are seldom used in real-time applications such as virtual environments and computer games. Since trimmed NURBS surfaces are often used to represent deformable objects, in this paper we present an efficient method for incremental rendering of deformable trimmed NURBS surfaces. A trimmed NURBS surface typically deforms through the deformation of the trimmed NURBS surface and/or the trimming curve. Our method handles both trimmed surface deformation as well as trimming curve deformation. Experimental results show that our method performs significantly faster than the method used in OpenGL and can be used in real-time applications, such as computer games. Copyright © 2006 John Wiley & Sons, Ltd.
1528533
Application, Network and Link Layer Measurements of Streaming Video over a Wireless Campus Network
The growth of wireless LANs has brought the expectation for high-bitrate streaming video to wireless PCs. However, it remains unknown how to best adapt video to wireless channel characteristics as they degrade. This paper presents results from experiments that stream commercial video over a wireless campus network and analyze performance across application, network and wireless link layers. Some of the key findings include: 1) Wireless LANs make it difficult for streaming video to gracefully degrade as network performance decreases; 2) Video streams with multiple encoding levels can more readily adapt to degraded wireless network conditions than can clips with a single encoding level; 3) Under degraded wireless network conditions, TCP streaming can provide higher video frame rates than can UDP streaming, but TCP streaming will often result in significantly longer playout durations than will UDP streaming; 4) Current techniques used by streaming media systems to determine effective capacity over wireless LAN are inadequate, resulting in streaming target bitrates significantly higher than can be effectively supported by the wireless network.
5198300
Compiler-directed channel allocation for saving power in on-chip networks
Increasing complexity in the communication patterns of embedded applications parallelized over multiple processing units makes it difficult to continue using the traditional bus-based on-chip communication techniques. The main contribution of this paper is to demonstrate the importance of compiler technology in reducing power consumption of applications designed for emerging multi processor, NoC (Network-on-Chip) based embedded systems. Specifically, we propose and evaluate a compiler-directed approach to NoC power management in the context of array-intensive applications, used frequently in embedded image/video processing. The unique characteristic of the compiler-based approach proposed in this paper is that it increases the idle periods of communication channels by reusing the same set of channels for as many communication messages as possible. The unused channels in this case take better advantage of the underlying power saving mechanism employed by the network architecture. However, this channel reuse optimization should be applied with care as it can hurt performance if two or more simultaneous communications are mapped onto the same set of channels. Therefore, the problem addressed in this paper is one of reducing the number of channels used to implement a set of communications without increasing the communication latency significantly. To test the effectiveness of our approach, we implemented it within an optimizing compiler and performed experiments using twelve application codes and a network simulation environment. Our experiments show that the proposed compiler-based approach is very successful in practice and works well under both hardware based and software based channel turn-off schemes.
2691860
Design and Management of 3D Chip Multiprocessors Using Network-in-Memory
Long interconnects are becoming an increasingly important problem from both power and performance perspectives. This motivates designers to adopt on-chip network-based communication infrastructures and three-dimensional (3D) designs where multiple device layers are stacked together. Considering the trends towards increasing use of chip multiprocessing, it is timely to consider 3D chip multiprocessor design and memory networking issues, especially in the context of data management in large L2 caches. The overall goal of this paper is to study the challenges for L2 design and management in 3D chip multiprocessors. Our first contribution is to propose a router architecture and a topology design that makes use of a network architecture embedded into the L2 cache memory. Our second contribution is to demonstrate, through extensive experiments, that a 3D L2 memory architecture generates much better results than the conventional two-dimensional (2D) designs under different number of layers and vertical (inter-wafer) connections. In particular, our experiments show that a 3D architecture with no dynamic data migration generates better performance than a 2D architecture that employs data migration. This also helps reduce power consumption in L2 due to a reduced number of data movements
1808525
A Compiler-Based Approach to Data Security
With the proliferation of personal electronic devices and embedded systems, personal and financial data is more easily accessible. As a consequence, we also observe a proliferation of techniques that attempt to illegally access sensitive data without proper authorization. Due to the severe financial and social ramifications of such data leakage, the need for secure memory has become critical. However, working with secure memories can have performance, power, and code size overheads since accessing a secure memory involves additional overheads for encryption/decryption and/or password checks. In addition, an application code may need to be restructured to work under such a memory system. In this paper, we propose a compiler-directed strategy to generate code for a secure memory based embedded architecture. The idea is to let the programmer mark certain data elements, called the seed elements, as secure (i.e., need to be stored in secure memory), and let the compiler determine the remaining secure elements automatically. We also address the problem of code size increase due to our strategy. The experimental results obtained through simulations clearly show that the proposed approach is effective in reducing the total secure memory size. The results also indicate that it is possible to reduce the resulting code size increase by clustering accesses to secure memory.
2888187
Asynchronous collaboration around multimedia and its application to on-demand training
Multimedia content is a central component of on-demand training and education delivered over the World Wide Web. Supporting asynchronous collaboration around educational multimedia is a key requirement for making the online educational environment effective. A multimedia annotation system tightly integrated with email provides a powerful platform on which to base such functionality. Building on our earlier work with multimedia annotations, we present user interface and system extensions to support asynchronous collaboration for on-demand training. We report results from a study of the effectiveness of the system, including student experience, instructor experience, and user interface appropriateness. Overall, the student experience was positive: they appreciated the flexibility of on-demand delivery and benefited from the collaborative features.