17132126
Recovery of material under complex illumination conditions
To calculate the inter-reflection between real objects and virtual ones in augmented reality, recovery of material for the real objects is necessary. In this paper, an approach is proposed to recover the material properties from a single high dynamic range image for a homogeneous object under complex illumination conditions. By the method, we first acquire a high dynamic range image for the object, and one or a few environment maps in high dynamic range as illumination of the object. Then a simulated annealing algorithm is employed to solve the inverse rendering problem. Finally, we obtain optimal parameter values for the reflection model in approximating the material of the object. In the course of optimization, image-based lighting and ray tracing techniques are used, and as a result the inter-reflection can be calculated in convenience. In addition, the transparent and translucent properties can be also recovered.
15500512
Real-time simulation of physically based on-surface flow
Although many papers have been published in the field of fluid simulation, little attention has been paid to on-surface flow involving wetting and stain transportation as well as erosion and deposition phenomena. In this paper, we introduce nonzero divergence in the mass equation of Navier–Stokes equations to simulate water penetration from on-surface flow into substrate material. Also, the volume of fluid method is adopted to track the free surface. With a computation of the actual amount of absorbed water we render the wetting effects with fully dry and fully wet texture images simultaneously. Using our model, the on-surface flow that accompanies water absorption can be simulated realistically in real time with OpenGL preview rendering. Experimental results illustrate that our model can be widely applied to solve various problems related to on-surface flow.
206530429
Point representation augmented to surface reconstruction in image-based VR
In this paper we propose a hybrid representation of environment models by a point representation augmented to geometric representation of surface polygons reconstructed from multiple reference images, through which a real time walkthrough of a complex environment can be achieved. By the method, we start from classification of pixels of the source images into two categories, corresponding respectively to the planar and non-planar surfaces in 3D space. For the pixels corresponding to the planar surfaces, the plane coefficients are reconstructed and all their appearances in the reference images are merged to form uniformly sampled texture images by a comparison of sampling rate and resampling. For the pixels corresponding to the non-planar surfaces, a point representation is applied and the redundant pixels are removed again through sampling rate comparison. The remained pixels are organized by OBB-tree according to their space coordinates. At the same time, the holes that are unable to be captured by all the reference images are pre-filled in the preprocessing phase so that the probability of hole appearance in walkthrough is greatly reduced. Under this hybrid representation, texture mapping and point warping are employed to render the novel views, to take full advantages of the acceleration utility of graphics hardware.
368408
A framework for opportunistic scheduling in wireless networks
Abstract We present a method, called opportunistic scheduling, for exploiting the time-varying nature of the radio environment to increase the overall performance of the system under certain quality of service/fairness requirements of users. We first introduce a general framework for opportunistic scheduling, and then identify three general categories of scheduling problems under this framework. We provide optimal solutions for each of these scheduling problems. All the proposed scheduling policies are implementable online; we provide parameter estimation algorithms and implementation procedures for them. We also show how previous work by us and others directly fits into or is related to this framework. We demonstrate via simulation that opportunistic scheduling schemes result in significant performance improvement compared with non-opportunistic alternatives.
10306588
Word Graphs: The Second Set
In continuation of the paper of Hoede and Li on word graphs for a set of prepositions, word graphs are given for adjectives, adverbs and Chinese classifier words. It is argued that these three classes of words belong to a general class of words that may be called adwords. These words express the fact that certain graphs may be brought into connection with graphs that describe the important classes of nouns and verbs. Some subclasses of adwords are discussed as well as some subclasses of Chinese classifier words.
2786167
Location-aware topology matching in P2P systems
Peer-to-peer (P2P) computing has emerged as a popular model aiming at further utilizing Internet information and resources, complementing the available client-server services. However, the mechanism of peers randomly choosing logical neighbors without any knowledge about underlying physical topology can cause a serious topology mismatching between the P2P overlay network and the physical underlying network. The topology mismatching problem brings a great stress in the Internet infrastructure and greatly limits the performance gain from various search or routing techniques. Meanwhile, due to the inefficient overlay topology, the flooding-based search mechanisms cause a large volume of unnecessary traffic. Aiming at alleviating the mismatching problem and reducing the unnecessary traffic, we propose a location-aware topology matching (LTM) technique, an algorithm of building an efficient overlay by disconnecting low productive connections and choosing physically closer nodes as logical neighbors while still retaining the search scope and reducing response time for queries. LTM is scalable and completely distributed in the sense that it does not require any global knowledge of the whole overlay network when each node is optimizing the organization of its logical neighbors. The effectiveness of LTM is demonstrated through simulation studies.
6185811
An efficient large deformation method using domain decomposition
Efficiently simulating large deformations of flexible objects is a challenging problem in computer graphics. In this paper, we present a physically based approach to this problem, using the linear elasticity model and a finite elements method. To handle large deformations in the linear elasticity model, we exploit the domain decomposition method, based on the observation that each sub-domain undergoes a relatively small local deformation, involving a global rigid transformation. In order to efficiently solve the deformation at each simulation time step, we pre-compute the object responses in terms of displacement accelerations to the forces acting on each node, yielding a force-displacement matrix. However, the force-displacement matrix could be too large to handle for densely tessellated objects. To address this problem, we present two methods. The first method exploits spatial coherence to compress the force-displacement matrix using the clustered principal component analysis method; and the second method pre-computes only the force-displacement vectors for the boundary vertices of the sub-domains and resorts to the Cholesky factorization to solve the acceleration for the internal vertices of the sub-domains. Finally, we present some experimental results to show the large deformation effects and fast performance on complex large scale objects under interactive user manipulations.
65741
WebDG - A Platform for E-Government Web Services
Web services are deemed as the natural choice for deploying e-government applications. Their use enables e-government to fully get advantage of the envisioned Semantic Web. In this paper, we propose WebDG, a comprehensive Web Service Management System for e-government applications. It aims to improve government-citizen interactions through an infrastructure built around the ”life experience” of citizens. WebDG provides a framework for automatically composing e-government services, optimized querying services, and preserving privacy.