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  • myhomepage
    Labs Research from 1978 until 2001 as Member of Technical Staff 1978 1991 and as Head of the Computing Principles Research Department 1991 2001 Then I was Director of Computing Principles Research at Avaya Labs 2001 2002 and Professor of Computer Science at Stanford University 2002 2003 I joined Columbia University in 2004 My research interests include design and analysis of algorithms complexity theory combinatorial optimization game theory databases and

    Original URL path: http://www.cs.columbia.edu/~mihalis/ (2016-02-17)
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  • Changxi Zheng's Homepage
    of a full head of hairs with over 150K strands in realtime We demonstrate the efficacy and robustness of our method with various hairstyles and driven motions e g head movement and wind force and compared against full simulation results that does not appear in the training data article Cai14 ARMI author Menglei Cai and Changxi Zheng and Kun Zhou title A Reduced Model for Interactive Hairs journal ACM Transactions on Graphics SIGGRAPH 2014 year 2014 volume 33 number 4 month Aug Xiang Chen Changxi Zheng Weiwei Xu and Kun Zhou An Asymptotic Numerical Method for Inverse Elastic Shape Design ACM Transactions on Graphics SIGGRAPH 2014 33 4 Paper PDF Project Page Abstract Bibtex Video Inverse shape design for elastic objects greatly eases the design efforts by letting users focus on desired target shapes without thinking about elastic deformations Solving this problem using classic iterative methods e g Newton Raphson methods however often suffers from slow convergence toward a desired solution In this paper we propose an asymptotic numerical method that exploits the underlying mathematical structure of specific nonlinear material models and thus runs orders of magnitude faster than traditional Newton type methods We apply this method to compute rest shapes for elastic fabrication where the rest shape of an elastic object is computed such that after physical fabrication the real object deforms into a desired shape We illustrate the performance and robustness of our method through a series of elastic fabrication experiments article Chen14 ANM author Xiang Chen and Changxi Zheng and Weiwei Xu and Kun Zhou title An Asymptotic Numerical Method for Inverse Elastic Shape Design journal ACM Transactions on Graphics Proceedings of SIGGRAPH 2014 year 2014 volume 33 number 4 month Aug Zherong Pan Jin Huang Yiying Tong Changxi Zheng and Hujun Bao Interactive Localized Liquid Motion Editing ACM Transactions on Graphics SIGGRAPH Asia 2013 32 6 Paper PDF Abstract Bibtex Video Animation techniques for controlling liquid simulation are challenging they commonly require carefully setting initial and boundary conditions or performing a costly numerical optimization scheme against user provided keyframes or animation sequences Either way the whole process is laborious and computationally expensive We introduce a novel method to provide intuitive and interactive control of liquid simulation Our method enables a user to locally edit selected keyframes and automatically propagates the editing in a nearby temporal region using geometric deformation We formulate our local editing techniques as a small scale nonlinear optimization problem which can be solved interactively With this uniformed formulation we propose three editing metaphors including i sketching local fluid features using a few user strokes ii dragging a local fluid region and iii controlling a local shape with a small mesh patch Finally we use the edited liquid animation to guide an of offline high resolution simulation to recover more surface details We demonstrate the intuitiveness and efficacy of our method in various practical scenarios article Pan 2013 author Zherong Pan and Jin Huang and Yiying Tong and Changxi Zheng and Hujun Bao title Interactive Localized Liquid Motion Editing journal ACM Transactions on Graphics SIGGRAPH Asia 2013 year 2013 month Nov volume 32 number 6 Changxi Zheng One to Many Example Based Mesh Animation Synthesis ACM SIGGRAPH Eurographics Symposium on Computer Animation SCA July 2013 Paper PDF Project Page Abstract Bibtex We propose an example based approach for synthesizing diverse mesh animations Provided a short clip of deformable mesh animation our method synthesizes a large number of different animations of arbitrary length Combining an automatically inferred linear blending skinning LBS model with a PCA based model reduction our method identifies possible smooth transitions in the example sequence To create smooth transitions we synthesize reduced deformation parameters based on a set of characteristic key vertices on the mesh Furthermore by analyzing cut nodes on a graph built upon the LBS model we are able to decompose the mesh into independent components Motions of these components are synthesized individually and assembled together Our method has the complexity independent from mesh resolutions enabling efficient generation of arbitrarily long animations without tedious parameter tuning and heavy computation We evaluate our method on various animation examples and demonstrate that numerous diverse animations can be generated from each single example inproceedings Zheng12 O2M author Changxi Zheng title One to Many Example Based Mesh Animation Synthesis booktitle Proceedings of the ACM SIGGRAPH Eurographics Symposium on Computer Animation series SCA 13 year 2013 month Jul url http www cs columbia edu cxz OneToMany Changxi Zheng and Doug L James Energy based Self Collision Culling for Arbitrary Mesh Deformations ACM Transactions on Graphics SIGGRAPH 2012 31 4 August 2012 Paper PDF Project Page Abstract Bibtex In this paper we accelerate self collision detection SCD for a deforming triangle mesh by exploiting the idea that a mesh cannot self collide unless it deforms enough Unlike prior work on subspace self collision culling which is restricted to low rank deformation subspaces our energy based approach supports arbitrary mesh deformations while still being fast Given a bounding volume hierarchy BVH for a triangle mesh we precompute Energy based Self Collision Culling ESCC certificates on bounding volume related sub meshes which indicate the amount of deformation energy required for it to self collide After updating energy values at runtime many bounding volume self collision queries can be culled using the ESCC certificates We propose an affine frame Laplacian based energy definition which sports a highly optimized certificate preprocess and fast runtime energy evaluation The latter is performed hierarchically to amortize Laplacian energy and affine frame estimation computations ESCC supports both discrete and continuous SCD detailed and nonsmooth geometry We demonstrate significant culling on various examples with SCD speed ups up to 26X article ZHENG12 ESCC author Changxi Zheng and Doug L James title Energy based Self Collision Culling for Arbitrary Mesh Deformations journal ACM Transactions on Graphics Proceedings of SIGGRAPH 2012 year 2012 volume 31 number 4 month Aug url http www cs cornell edu projects escc Jeffrey N Chadwick Changxi Zheng and Doug L James Precomputed Acceleration Noise for Improved Rigid Body Sound ACM Transactions on Graphics SIGGRAPH 2012 31 4 August 2012 Paper PDF Project Page Abstract Bibtex We introduce an efficient method for synthesizing acceleration noise due to rigid body collisions using standard data provided by rigid body solvers We accomplish this in two main steps First we estimate continuous contact force profiles from rigid body impulses using a simple model based on Hertz contact theory Next we compute solutions to the acoustic wave equation due to short acceleration pulses in each rigid body degree of freedom We introduce an efficient representation for these solutions Precomputed Acceleration Noise which allows us to accurately estimate sound due to arbitrary rigid body accelerations We find that the addition of acceleration noise significantly complements the standard modal sound algorithm especially for small objects article Chadwick12 author Jeffrey N Chadwick and Changxi Zheng and Doug L James title Precomputed Acceleration Noise for Improved Rigid Body Sound journal ACM Transactions on Graphics Proceedings of SIGGRAPH 2012 year 2012 volume 31 number 4 month Aug url http www cs cornell edu projects Sound impact Jeffrey N Chadwick Changxi Zheng and Doug L James Faster Acceleration Noise for Multibody Animations using Precomputed Soundbanks ACM Eurographics Symposium on Computer Animation SCA July 2012 Paper PDF Project Page Abstract Bibtex We introduce an efficient method for synthesizing rigid body acceleration noise for complex multibody scenes Existing acceleration noise synthesis methods for animation require object specific precomputation which is prohibitively expensive for scenes involving rigid body fracture or other sources of small procedurally generated debris We avoid precomputation by introducing a proxy based method for acceleration noise synthesis in which precomputed acceleration noise data is only generated for a small set of ellipsoidal proxies and stored in a proxy soundbank Our proxy model is shown to be effective at approximating acceleration noise from scenes with lots of small debris e g pieces produced by rigid body fracture This approach is not suitable for synthesizing acceleration noise from larger objects with complicated non convex geometry however it has been shown in previous work that acceleration noise from objects such as these tends to be largely masked by modal vibration sound We manage the cost of our proxy soundbank with a new wavelet based compression scheme for acceleration noise and use our model to significantly improve sound synthesis results for several multibody animations article Chadwick12 SCA author Jeffrey N Chadwick and Changxi Zheng and Doug L James title Faster Acceleration Noise for Multibody Animations using Precomputed Soundbanks journal ACM Eurographics Symposium on Computer Animation year 2012 month July url http www cs cornell edu projects Sound proxy Changxi Zheng and Doug L James Toward High Quality Modal Contact Sound ACM Transactions on Graphics SIGGRAPH 2011 30 4 August 2011 Paper PDF Project Page Abstract Bibtex Contact sound models based on linear modal analysis are commonly used with rigid body dynamics Unfortunately treating vibrating objects as rigid during collision and contact processing fundamentally limits the range of sounds that can be computed and contact solvers for rigid body animation can be ill suited for modal contact sound synthesis producing various sound artifacts In this paper we resolve modal vibrations in both collision and frictional contact processing stages thereby enabling non rigid sound phenomena such as micro collisions vibrational energy exchange and chattering We propose a frictional multibody contact formulation and modified Staggered Projections solver which is well suited to sound rendering and avoids noise artifacts associated with spatial and temporal contact force fluctuations which plague prior methods To enable practical animation and sound synthesis of numerous bodies with many coupled modes we propose a novel asynchronous integrator with model level adaptivity built into the frictional contact solver Vibrational contact damping is modeled to approximate contact dependent sound dissipation Results are provided that demonstrate high quality contact resolution with sound article ZHENG11 author Changxi Zheng and Doug L James title Toward High Quality Modal Contact Sound journal ACM Transactions on Graphics Proceedings of SIGGRAPH 2011 year 2011 volume 30 number 4 month Aug url http www cs cornell edu projects Sound mc Changxi Zheng and Doug L James Rigid Body Fracture Sound with Precomputed Soundbanks ACM Transactions on Graphics SIGGRAPH 2010 29 3 July 2010 Paper PDF Project Page Abstract Bibtex We propose a physically based algorithm for synthesizing sounds synchronized with brittle fracture animations Motivated by laboratory experiments we approximate brittle fracture sounds using time varying rigid body sound models We extend methods for fracturing rigid materials by proposing a fast quasistatic stress solver to resolve near audio rate fracture events energy based fracture pattern modeling and estimation of crack related fracture impulses Multipole radiation models provide scalable sound radiation for complex debris and level of detail control To reduce soundmodel generation costs for complex fracture debris we propose Precomputed Rigid Body Soundbanks comprised of precomputed ellipsoidal sound proxies Examples and experiments are presented that demonstrate plausible and affordable brittle fracture sounds article ZHENG10 author Changxi Zheng and Doug L James title Rigid Body Fracture Sound with Precomputed Soundbanks journal ACM Transactions on Graphics Proceedings of SIGGRAPH 2010 year 2010 volume 29 number 3 month jul url http www cs cornell edu projects fracturesound Changxi Zheng and Doug L James Harmonic Fluids ACM Transactions on Graphics SIGGRAPH 2009 28 3 August 2009 Paper PDF Project Page Abstract Bibtex Fluid sounds such as splashing and pouring are ubiquitous and familiar but we lack physically based algorithms to synthesize them in computer animation or interactive virtual environments We propose a practical method for automatic procedural synthesis of synchronized harmonic bubble based sounds from 3D fluid animations To avoid audio rate time stepping of compressible fluids we acoustically augment existing incompressible fluid solvers with particle based models for bubble creation vibration advection and radiation Sound radiation from harmonic fluid vibrations is modeled using a time varying linear superposition of bubble oscillators We weight each oscillator by its bubble to ear acoustic transfer function which is modeled as a discrete Green s function of the Helmholtz equation To solve potentially millions of 3D Helmholtz problems we propose a fast dual domain multipole boundary integral solver with cost linear in the complexity of the fluid domain s boundary Enhancements are proposed for robust evaluation noise elimination acceleration and parallelization Examples of harmonic fluid sounds are provided for water drops pouring babbling and splashing phenomena often with thousands of acoustic bubbles and hundreds of thousands of transfer function solves article ZHENG09 author Changxi Zheng and Doug L James title Harmonic Fluids journal ACM Transactions on Graphics Proceedings of SIGGRAPH 2009 year 2009 volume 28 number 3 month Aug url http www cs cornell edu projects HarmonicFluids Wireless Networking Justin Chan Changxi Zheng and Xia Zhou 3D Printing Your Wireless Coverage ACM Workshop on Hot Topics in Wireless HotWireless 2015 Hot Paper Award Paper PDF Abstract Bibtex Video Directing wireless signals and customizing wireless coverage is of great importance in residential commercial and industrial environments It can improve the wireless reception quality reduce the energy consumption and achieve better security and privacy To this end we propose WiPrint a new computational approach to control wireless coverage by mounting signal reflectors in carefully optimized shapes on wireless routers Leveraging 3D reconstruction fast wave simulations in acoustics computational optimization and 3D fabrication our method is low cost adapts to different wireless routers and physical environments and has a far reaching impact by interweaving computational techniques to solve key problems in wireless communication inproceedings Chan2015 author Chan Justin and Zheng Changxi and Zhou Xia title 3D Printing Your Wireless Coverage booktitle Proceedings of the 2nd International Workshop on Hot Topics in Wireless series HotWireless 15 year 2015 pages 1 5 numpages 5 publisher ACM address New York NY USA Changxi Zheng Lusheng Ji Dan Pei Jia Wang and Paul Francis A Light Weight Distributed Scheme for Detecting IP Prefix Hijacks in Real time Proc of ACM SIGCOMM Kyoto Japan August 2007 Paper PDF Abstract Bibtex As more and more Internet IP prefix hijacking incidents are being reported the value of hijacking detection services has become evident Most of the current hijacking detection approaches monitor IP prefixes on the control plane and detect inconsistencies in route advertisements and route qualities We propose a different approach that utilizes information collected mostly from the data plane Our method is motivated by two key observations when a prefix is not hijacked 1 the hop count of the path from a source to this prefix is generally stable and 2 the path from a source to this prefix is almost always a super path of the path from the same source to a reference point along the previous path as long as the reference point is topologically close to the prefix By carefully selecting multiple vantage points and monitoring from these vantage points for any departure from these two observations our method is able to detect prefix hijacking with high accuracy in a light weight distributed and real time fashion Through simulations constructed based on real Internet measurement traces we demonstrate that our scheme is accurate with both false positive and false negative ratios below 5 inproceedings Zheng 2007 author Zheng Changxi and Ji Lusheng and Pei Dan and Wang Jia and Francis Paul title A light weight distributed scheme for detecting ip prefix hijacks in real time booktitle Proceedings of the 2007 conference on Applications technologies architectures and protocols for computer communications series SIGCOMM 07 year 2007 location Kyoto Japan pages 277 288 numpages 12 publisher ACM address New York NY USA Applied Math Alexander Vladimirsky and Changxi Zheng A fast implicit method for time dependent Hamilton Jacobi PDEs Under review Preprint Project Page Abstract Source Code We present a new efficient computational approach for time dependent first order Hamilton Jacobi Bellman PDEs Since our method is based on a time implicit Eulerian discretization the numerical scheme is unconditionally stable but discretized equations for each time slice are coupled and non linear We show that the same system can be re interpreted as a discretization of a static Hamilton Jacobi Bellman PDE on the same physical domain The latter was shown to be causal in Vladimirsky 2006 making fast non iterative methods applicable The implicit discretization results in higher computational cost per time slice compared to the explicit time marching However the latter is subject to a CFL stability condition and the implicit approach becomes significantly more efficient whenever the accuracy demands on the time step are less restrictive than the stability We also present a hybrid method which aims to combine the advantages of both the explicit and implicit discretizations We demonstrate the efficiency of our approach using several examples in optimal control of isotropic fixed horizon processes Robotics Yun Jiang Marcus Lim Changxi Zheng and Ashutosh Saxena Learning to Place New Objects in a Scene In International Journal of Robotics Research IJRR 2012 Paper PDF Project Page Abstract Bibtex Placing is a necessary skill for a personal robot to have in order to perform tasks such as arranging objects in a disorganized room The object placements should not only be stable but also be in their semantically preferred placing areas and orientations This is challenging because an environment can have a large variety of objects and placing areas that may not have been seen by the robot before In this paper we propose a learning approach for placing multiple objects in different placing areas in a scene Given point clouds of the objects and the scene we design appropriate features and use a graphical model to encode various properties such as the stacking of objects stability object area relationship and common placing constraints The inference in our model is an integer linear program which we solve efficiently via an LP relaxation We extensively evaluate our approach on 98 objects from 16 categories being placed into 40 areas Our robotic experiments show a success rate of 98 in placing known objects and 82 in placing new objects stably We use

    Original URL path: http://www.cs.columbia.edu/~cxz/publications.htm (2016-02-17)
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  • Changxi Zheng's Homepage
    with very talented students at Columbia Computer Graphics Group In particular I served and have been serving as an advisor of a group of excellent students and researchers Current Students Dingzeyu Li Ph D CS Timothy Sun Ph D CS Yun Fei Ph D CS co advising with Eitan Grinspun Visitors Gabriel Cirio Visiting Postdoc Xiang Chen Visiting Scholar Zhejiang University Former Ante Qu Princeton summer intern next Microsoft Vinicius

    Original URL path: http://www.cs.columbia.edu/~cxz/research.htm (2016-02-17)
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  • Changxi Zheng's Homepage
    University Courses Spring 2016 COMS W4162 Advanced Computer Graphics Fall 2015 COMS W4167 Computer Animation Spring 2015 COMS W4160 Computer Graphics Fall 2014 COMS W4162 Advanced Computer Graphics Spring 2014 COMS W4160 Computer Graphics Fall 2013 COMS E6998 2 Graphics

    Original URL path: http://www.cs.columbia.edu/~cxz/teaching.htm (2016-02-17)
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  • Changxi Zheng's Homepage
    Shape Change the Sound Making New Music with 3D Printed Metallophone Instruments Zoolophone features custom shaped keys that still produce the right notes Would you like to play this 3D printed zoolophone Algorithm to 3 D print vibrational sounds Zoolophone musical instrument made of animal shapes Computational Hydrographic Printing Coloring Complex 3D Printed Objects New Computational Technique Advances Color 3D Printing Process Precision Hydrographic Printing A Fascinating New Way to Precisely Add Color to 3D Prints Crazy Way To Paint Patterns On 3 D Objects Is Like A Cartoon Come To Life WATCH THIS FUTURISTIC VAT OF WATER PAINT A CAT A Crazy Way to Add Intricate Color to 3 D Printed Creations Hydrographic Printing Affordable Full Color Prints for Everyone New computational technique advances color 3D printing process Computational Design of Twisty Joints and Puzzles How to Turn Any Object Into a Rubik s Cube 3 D Print and Rubik s Cube ify Almost Anything Transform Any Object Into a Rubikâ s Cube With Twisty Joints This New Software Turns Any Object Into a Rubik s Cube Puzzle New Software Turns Any 3D Printable Model into a Rubikâ s Cube Style Twisty Puzzle Columbia Researchers Develop Software That Converts

    Original URL path: http://www.cs.columbia.edu/~cxz/press.htm (2016-02-17)
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  • Bioinformatics Columbia University Computer Science W4761

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    Original URL path: /4761/ (2016-02-17)


  • Yechiam Yemini (YY) is a Professor of computer science at Columbia University
    dcc He is currently teaching the Computational Genomics class W4761 visit www cs columbia edu 4761 for extensive course notes Professor Yemini has also been a co founder of Comverse Technology 1983 http www comverse com System Management Arts SMARTS 1993 http www smarts com acquired by EMC in 2005 and Arootz 2006 http www arootz com He has served as a director and advisory board member of several high

    Original URL path: http://www.cs.columbia.edu/~yemini/ (2016-02-17)
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  • People
    Singh PhD Student Office 517 CS Bldg Tel 212 939 7065 Fax 212 666 0140 montek at cs columbia edu personal home page Michael Theobald PhD Student Office 517 CS Bldg Tel 212 939 7065 Fax 212 666 0140 theobald cs columbia edu personal home page Tiberiu Chelcea PhD Student Office 504 CS Bldg Tel 212 939 7052 Fax 212 666 0140 tibi cs columbia edu personal home page Garry

    Original URL path: http://www.cs.columbia.edu/async/people.html (2016-02-17)
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