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Radiance-based color calibration for image-based modeling with multiple cameras

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Science china(Information Sciences) 2012年第7期55卷 1509-1519页

作者： ZHAO Xu 1,2 ,zhou zhong 1,2 & wu wei 1,2 1 state key laboratory of virtual reality technology and systems,beihang university,beijing 100191,china 2 School of Computer Science and Engineering,beihang university,beijing 100191,china 1. state key laboratory of virtual reality technology and systems Beihang University Beijing 100191 China2. School of Computer Science and Engineering Beihang University Beijing 100191 China

Photo-consistency estimation is an important part for many image-based modeling *** paper presents a novel radiance-based color calibration method to reduce the uncertainty of photo-consistency estimation across multiple *** idea behind our method is to convert colors into a uniform radiometric color space in which multiple image data are *** results demonstrate that our method can achieve comparable color calibration effect without adjusting camera parameters and is more robust than other existing ***,we obtain an auto-determined threshold for photo-consistency check,which will lead to a better performance than existing photo-consistency based reconstruction algorithms.

关键词： color calibration photo-consistency estimation multi-camera system image-based modeling

Displacement residual based DDM matching algorithm

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Science china(Information Sciences) 2012年第9期55卷 2090-2101页

作者： ZHANG Lin 1,2,zhou zhong 1,2,LIU Lin 1,2 & wu wei 1,2 1 state key laboratory of virtual reality technology and systems,beihang university,beijing 100191,china 2 School of Computer Science and Engineering,beihang university,beijing 100191,china 1. state key laboratory of virtual reality technology and systems Beihang University Beijing 100191 China2. School of Computer Science and Engineering Beihang University Beijing 100191 China

High level architecture(HLA) is the prevailing standard for modeling and *** data distribution management(DDM) service of HLA is defined for reducing the delivery of irrelevant *** key in DDM implementation is the region overlap computation,*** matching between update and subscription *** algorithms usually make a compromise between region fidelity and network *** paper takes both the matching algorithm efficiency and bandwidth cost into *** main contributions are:1) illustrating the relationship between region changes and overlap changes,as helps reduce the number of region matching and then improves the total matching efficiency;2) classifying region updates into two types of data expression,snapshot and *** network traffic will be reduced by transmitting only residual data instead of full region representations ***,a region matching algorithm called displacement residual-based DDM matching(DRBM) is proposed in the *** analysis,algorithm implementation and experiment evaluation are *** results show that DRBM provides better matching performance and significant network payload reductions especially when there is a large number of changing regions.

关键词： distributed simulation high level architecture data distribution management region snapshot region residual

Gray physical interference model based link scheduling algorithms

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Science china(Information Sciences) 2012年第6期55卷 1337-1350页

作者： SU JinZhao 1,2,CAO Jing 1,2 & wu wei 1,2 1 state key laboratory of virtual reality and systems,beijing 100191,china 2 School of Computer Science and Engineering,beihang university,beijing 100191,china 1. state key laboratory of virtual reality and systems Beijing 100191 China2. School of Computer Science and Engineering Beihang University Beijing 100191 China

To improve the concurrent data transmission capability of wireless multi-hop networks,this paper proposes adopting a gray physical interference model instead of using the threshold physical interference *** model allows non-ideal links to be involved in scheduling,under the premise of not affecting the quality of existing transmission *** addition,we design two greedy algorithms to schedule more links with SINR values located in the transition *** results show that a gray physical interference model is more accurate than a threshold physical interference one,the concurrent transmission capability of a network based on the gray physical interference model is significantly increased,and network throughput is increased by 20%.

关键词： gray physical interference model threshold physical interference model link scheduling concurrent transmission TDMA

Data acquisition and simulation of natural phenomena

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Science china(Information Sciences) 2011年第4期54卷 683-716页

作者： ZHAO QinPing state key laboratory of virtual reality technology and systems,beihang university,beijing 100191,china 1. state key laboratory of virtual reality technology and systems Beihang University Beijing 100191 China

virtual natural phenomena obtained through mathematical-physical modeling and simulation as well as graphics emulation can meet the user’s requirements for sensory experiences to a certain extent but they can hardly have the same accurate physical consistency as real natural *** technology for data acquisition and natural phenomena simulation can enable us to obtain multi-dimensional and multi-modal data directly from real natural phenomena and,based on these real data,to establish digital models highly consistent with real natural phenomena in appearance,physics,behavior or many other aspects,thus making a virtual natural phenomenon a direct mapping of real natural *** approach is conducive to resolving problems concerning the reliability and availability of virtual *** present the technology for acquiring and simulating dada of natural phenomena is still in its initial *** paper gives a review of the related ***,we briefly introduce the basic methods and techniques concerned,then,based on the difference between the basic elements of various natural phenomena,we discuss the current studies on such natural phenomena as light,water,fire,smoke,dynamic terrain,etc.,and finally,in connection with issues in the present research and possible future direction of development,we put forth a number of theoretical and technical problems,hoping they can be resolved in the near future.

关键词： natural phenomena data acquisition simulation data driven reliability

Algorithm of simulation time synchronization over large-scale nodes

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Science in china(Series F) 2008年第9期51卷 1239-1255页

作者： ZHAO QinPing1,2,zhou zhong1,2 & Lü Fang1,2 1 state key laboratory of virtual reality technology and systems,beihang university,beijing 100083,china 2 School of Computer Science and Engineering,beihang university,beijing 100083,china state key laboratory of virtual reality technology and systems Beihang University Beijing 100083 China School of Computer Science and Engineering Beihang University Beijing 100083 China

In distributed simulation, there is no uniform physical clock. And delay cannot be estimated because of jitter. So simulation time synchronization is essential for the event consistency among nodes. This paper investigates time synchronization algorithms over large-scale distributed nodes, analyzes LBTS （lower bound time stamp） computation model described in IEEE HLA standard, and then presents a grouped LBTS model. In fact, there is a default premise for existing algorithms that controi packets must be delivered via reliable transportation. Although, a theorem of time synchronization message＇s reliability is proposed, which proves that only those control messages that constrain time advance need reliability. It breaks out the default premise for reliability. Then multicast is introduced into the transmis- sion of control messages, and algorithm MCTS （multi-node coordination time synchronization） is proposed based on multicast. MCTS not only promotes the time advance efficiency, but also reduces the occupied network bandwidth. Experiment results demonstrate that the algorithm is better than others in both time advance speed and occupied network bandwidth. Its time advance speed is about 50 times per second when there are 1000 nodes, approximately equal to that of similar systems when there are 100 nodes.

关键词： distributed simulation time synchronization multi-node coordination LBTS multicast

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Image-based modeling of inhomogeneous single-scattering participating media

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Science china(Information Sciences) 2010年第6期53卷 1141-1150页

作者： HU Yong 1 , QI Yue 1 & TONG Xin 2 1 state key laboratory of virtual reality technology and systems, beihang university, beijing 100191, china 2 Microsoft Research Asia, beijing 100080, china 1. state key laboratory of virtual reality technology and systems Beihang University Beijing 100191 China2. Microsoft Research Asia Beijing 100080 China

We propose a method to reconstruct inhomogeneous single-scattering participating media, which could preserve fine high-frequency details of density *** data and the ratio of absorption coefficient to scattering coefficient are used to describe the spatial-varying density distribution and optical properties of certain participating media, and a function between the above parameters and captured pixel values is *** the problem of how to find solutions to these parameters is formulated into a nonlinear numerical optimization *** order to reduce large time overheads and numerical instability brought by simultaneously solving large numbers of voxels, we propose an initialization algorithm for enabling the assigned density values to satisfy the regularity of brightness distribution in captured images approximately as well as a progressive refinement algorithm for multi-resolution volumetric ***, we propose a parallel multi-voxel gradient computation algorithm of utilizing hardware acceleration to reduce time overheads in gradient computation for large numbers of *** results indicate that our method is well suited for reconstructing thin smoke, retaining high-frequency details from images captured from multiple viewpoints.

关键词： single-scattering participating media smoke modeling volumetric modeling image based modeling

Simultaneous structure and geometry detail completion based on interactive user sketches

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Science china(Information Sciences) 2012年第5期55卷 1123-1137页

作者： YANG Shen 1,QI Yue 1 & QIN Hong 2 1 state key laboratory of virtual reality technology and systems,beihang university,beijing 100191,china 2 Department of Computer Science,state university of New York at Stony Brook,Stony Brook,New York 11794-4400,USA 1. state key laboratory of virtual reality technology and systems Beihang University Beijing 100191 China2. Department of Computer Science State University of New York at Stony Brook Stony Brook New York 11794-4400 USA

We articulate a novel approach to geometric model completion via interactive sketches in this ***,the initial incomplete model (with holes) is decomposed into a base model and a high-frequency component,which represents global rough shape and geometric details,*** then repair the base model via smooth hole-filling,and compute the geometry detail image using high frequency *** novel element of our approach is that we allow users to interactively sketch a few structural curves that span across hole regions,with a goal to repair both local geometric details and global *** the help of local parameterization,we convert detailed geometry into gradient-domain images which can propagate along user-specified *** integrating recovered gradient-domain images and base shape,we can generate a complete model that faithfully recovers both global structure and local *** salient contribution of this paper is the unified approach for user interaction,global structure,and geometry details towards high-fidelity model *** demonstrate our new approach using a number of examples that exhibit salient global structure as well as local geometry details.

关键词： model repair geometric modeling interactive sketch 3D graphics

Video motion stitching using trajectory and position similarities

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Science china(Information Sciences) 2012年第3期55卷 600-614页

作者： CHEN Xiaowu, LI Qing , LI Xin & ZHAO QinPing state key laboratory of virtual reality technology and systems, School of Computer Science and Engineering, beihang university, beijing 100191, china 1. state key laboratory of virtual reality technology and systems School of Computer Science and Engineering Beihang University Beijing 100191 China

Stitching motions in multiple videos into a single video scene is a challenging task in current video fusion and mosaicing research and film production. In this paper, we present a novel method of video motion stitching based on the similarities of trajectory and position of foreground objects. First, multiple video sequences are registered in a common reference frame, whereby we estimate the static and dynamic backgrounds, with the former responsible for distinguishing the foreground from the background and the static region from the dynamic region, and the latter functioning in mosaicing the warped input video sequences into a panoramic video. Accordingly, the motion similarity is calculated by reference to trajectory and position similarity, whereby the corresponding motion parts are extracted from multiple video sequences. Finally, using the corresponding motion parts, the foregrounds of different videos and dynamic backgrounds are fused into a single video scene through Poisson editing, with the motions involved being stitched together. Our major contributions are a framework of multiple video mosaicing based on motion similarity and a method of calculating motion similarity from the trajectory similarity and the position similarity. Experiments on everyday videos show that the agreement of trajectory and position similarities with the real motion similarity plays a decisive role in determining whether two motions can be stitched. We acquire satisfactory results for motion stitching and video mosaicing.

关键词： video fusion video mosaicing video registration background estimation motion stitching

Experimental study of gas-water elongated bubble flow during production logging

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Petroleum Science 2011年第2期8卷 157-162页

作者： Lu Jing wu Xiling key laboratory of Earth Prospecting and Information technology China University of Petroleum Beijing 102249 China state key laboratory of Petroleum Resource and Prospecting China University of Petroleum Beijing 102249 China

In order to improve the interpretation of production log data on gas-water elongated bubble （EB） flow in horizontal wells, a multi-phase flow simulation device was set up to conduct a series of measurement experiments using air and tap water as test media, which were measured using a real production logging tool （PLT） string at different deviations and in different mixed flow states. By understanding the characteristics and mechanisms of gas-water EB flow in transparent experimental boreholes during production logging, combined with an analysis of the production log response characteristics and experimental production logging flow pattern maps, a method for flow pattern identification relying on log responses and a drift-flux model were proposed for gas-water EB flow. This model, built upon experimental data of EB flow, reveals physical mechanisms of gas-water EB flow during measurement processing. The coefficients it contains are the specific values under experimental conditions and with the PLT string used in our experiments. These coefficients also reveal the interference with original downhole flow patterns by the PLT string. Due to the representativeness that our simulated flow experiments and PLT string possess, the model coefficients can be applied as empirical values of logging interpretation model parameters directly to real production logging data interpretation, when the measurement circumstances and PLT strings are similar.

关键词： Horizontal wells elongated bubble flow flow patterns identification drift-flux model,logging interpretation model

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