Liu Ren

LIU REN
918 Bellefonte Street Phone: (412) 965-9370
Pittsburgh, PA Email: williamren@gmail.com

15232 Website: http://www.cs.cmu.edu/~liuren

OBJECTIVE

Computer Scientist (Ph.D.) with expertise in R&D for character animation, real-time rendering, vision graphics, machine learning, and scientific visualization seeking position to design and develop novel graphics applications.

SKILLS SUMMARY

Expert in data-driven character animation, performance animation, motion capture processing, video-based animation, real-time point and volume rendering, machine learning techniques in character animation and statistical analysis of natural human motion.
Expert in architecting, designing, implementing, testing, and deploying computer animation systems to handle large motion capture databases.
Experienced in image-based rendering and modeling, cloth and rigid-body simulation, character skinning, image and video processing, mesh decimation and processing with appearance attributes, ray-tracing, texture synthesis and non-photorealistic rendering.
Strong background in computer graphics, computer vision, and machine learning techniques.
Programming languages: C/C++, Matlab, Programmable Vertex and Pixel Shaders.
Libraries: DirectX, OpenGL, FLTK, GLUT, MFC, BOOST C++, CGAL, IPL, MPI.
Software: Adobe After Effects, Adobe Illustrator, Vicon BodyBuilder, Maya, Oracle, LaTeX, and most PC software.
Operating systems: Windows 2000/XP, Linux, Beowulf system.
Strong system builder, experienced presenter, and team player.
Experienced in working with artists in animation projects.
Fluent in English and native in Chinese (Mandarin).

EDUCATION

Carnegie Mellon University, Pittsburgh, PA

Ph.D. in Computer Science Department September 2006

Advisor: Prof. Jessica K. Hodgins
M.Sc. in Computer Science Department December 2004

Advisor: Prof. Jessica K. Hodgins

Zhejiang University, Hangzhou, China
M.S.E.   in Computer Science and Engineering Department (with honor)                               February 1999

Advisor: Prof. Weidong Geng and Prof. Yunhe Pan
B.E. in Computer Science and Engineering Department (with honor) July 1996

Advisor: Prof. Weidong Geng and Prof. Yunhe Pan

PROFESSIONAL EXPERIENCE

Carnegie Mellon University, Computer Science Department, Pittsburgh, PA September 1999 – Present

Research Associate/Research Assistant/Technology Specialist

Character Animation (January 2002 – Present)

Designed and implemented a new technique for synergy identification in human motion. Typical applications include marker selection for performance animation systems when a reduced marker set is employed and automatic animation quality evaluation [in preparation for TOG 2006].
Explored the statistics of natural human motion for natural motion synthesis in character animation [in preparation for TOG 2006].
Designed and implemented a new visualization technique for motion capture database [in preparation for TOG 2006].

Designed and implemented a novel ensemble approach to classify natural vs. unnatural motion using a large motion capture database [SIGGRAPH/TOG 2005].
Designed and implemented a new video-camera-based (markerless) performance animation system with four key components including online image and video processing, online motion retrieval, offline training procedures using AdaBoost and augmented motion graphs for two characters [TOG 2005]

Hardware-Accelerated Rendering (July 2001 – May 2004)

Designed and worked on the first GPU-based approach for real-time volume splatting with high quality anisotropic texture filtering (EWA filtering) (two patents pending) [IEEE VIS 2004].

Designed and implemented the first GPU-based approach for real-time point rendering with high quality anisotropic texture filtering (EWA filtering) (two patents pending) [EUROGRAPHICS 2002] .

Image-Based Rendering (September 1999 – June 2001)

Designed and implemented a fast image warping algorithm using multigrid.
Developed a hole filling method for view transformation using texture synthesis.
Developed an efficient light field rendering algorithm.

Mitsubishi Electric Research Lab (MERL), MA. May 2003 – August 2003

Summer intern

Designed and implemented a fast feature selection procedure using AdaBoost on a 100-node Beowulf system.
Sped up the offline learning part of our performance animation system (reduced the required training time from 104 days on 100 nodes to less than 3 days on 50 nodes.

Mitsubishi Electric Research Lab (MERL), MA. May 2001 – August 2001

Summer Intern

Designed and implemented the first hardware-accelerated approach to EWA surface splatting [EUROGRAPHICS 2002, two patents applied for].

Raindrop Geomagic, NC. May 2000 – August 2000

Summer intern

Designed and implemented topology and curvature preserving surface decimation with appearance attributes (color and multiple texture maps) for Geomagic Studio.

Zhejiang University, Computer Science Department, Hangzhou, China August 1997 – January 1999

Research Assistant

Designed and implemented an interactive pen-and-ink illustration system based on a new method called "Case-based Rendering” that allowed the system to learn different styles of the artists and generate different tone styles of pen-and-ink illustrations automatically from an input grayscale image [APAC 1999].

TEACHING AND MENTORING EXPERIENCE

Carnegie Mellon University, Computer Science Department, Pittsburgh, PA January 2001 – May 2006

Teaching Assistant

2006, CMU undergraduate course 15-462, Introduction to Computer Graphics

Presented lectures and review sessions. Designed and graded homework. Assisted with projects and exams. Held office hours.

2001, CMU undergraduate course 15-463, Advanced Computer Graphics

Assisted with the design and grading of homework, exams and projects. Held office hours.

Mentor

2002, Michael Stevens, CMU CSD freshman and CMU motion capture lab staff.

Taught character skinning in Maya, motion capture data processing, camera calibration and basic image and video processing techniques.

SELECTED PUBLICATIONS[DBLP|Google Scholar Citation]

Character animation:

Liu Ren and Jessica Hodgins, “Exploring the Statistics of Natural Human Motion”, ACM Transactions on Graphics (TOG), 2006 (In Preparation).
Liu Ren, Alton Patrick, Alexei Efros, Jessica Hodgins, and James Rehg, “A Data-Driven Approach to Quantifying Natural Human Motion”, ACM Transactions on Graphics (SIGGRAPH 2005), August, pp. 1090-1097, July, vol. 24(3), 2005.

Liu Ren, Gregory Shakhnarovich, Jessica Hodgins, Hanspeter Pfister and Paul Viola, “Learning Silhouette Features for Control of Human Motion”, ACM Transactions on Graphics (TOG), pp. 1303-1331, October, vol. 24(4), 2005. Also presented as a sketch at SIGGRAPH2004.

Hardware-accelerated rendering:

Wei Chen, Liu Ren, Matthias Zwicker and Hanspeter Pfister, “Adaptive EWA Splatting”, IEEE Transactions on Visualization and Computer Graphics (TVCG) 2006 (In Preparation).
Wei Chen, Liu Ren, Matthias Zwicker and Hanspeter Pfister, “Hardware-Accelerated Adaptive EWA Volume Splatting”, IEEE Visualization 2004, pp. 67-74, October, 2004 (Patent Pending).
Liu Ren, Hanspeter Pfister and Matthias Zwicker, “Object Space EWA Surface Splatting: A Hardware Accelerated Approach to High Quality Point Rendering”, Computer Graphics Forum 21(3)(EUROGRAPHICS 2002, Best Paper Nominee), pp. 461-470, vol. 31(3), September, 2002 (Patent Pending).

Nonphotorealistic rendering and AI:

Weidong Geng and Liu Ren, “Nonphotorealistic Rendering Methods for Pen-and-ink Illustration”, Academic Periodical Abstracts of China, Vol. 5(3), 1999.
Liu Ren, Weidong Geng and Yunhe Pan, “A New Approach to Scheme Design Oriented Generation of Architectural Plan”, Journal of CAD & CG, pp. 555-558, vol. 11(6), 1999.

SELECTED GRADUATE COURSES

Computer Animation, Data-driven Character Animation, Physically-Based Character Animation, Computer Vision, Image and Video Processing, Image-based Rendering and Modeling, Computer Networking, Algorithms, Computer Architecture, Advanced AI Concepts, Introduction to Scientific Computing, Semantics of Sequential and Parallel Algorithms.

PROFESSIONAL ACTIVITIES
Reviewer for ACM SIGGRAPH, ACM Transactions on Graphics (TOG), IEEE Transactions on Visualization and Computer Graphics (TVCG), Eurographics, ACM Symposium on Computer Animation, ACM Symposium on Geometry Processing, ACM Symposium on Point Rendering.

AWARDS

Carnegie Mellon University SCS Alumni Fellowship, 2001-2002
Carnegie Mellon University Graduate Fellowship, 1999- 2005.
Zhejiang University Excellent Graduate Award, May 1999.
Zhejiang University Academic Scholarship, 1992 -1999.
Zhejiang University Excellent Graduate Award, July 1996.
Mixed Class (Elite Class in Zhejiang University) Honored Student Award, May 1994.