Weiwei Xu

 

Hangzhou Normal University

 

5th Floor, Sigma Center, No. 49 ZhiChun Road, HaiDian,

Beijing, 100190, P. R. China

Email: weiwei.xu.g@ gmail.com

Tel:  86-10-59175197

 

About Me

I am now a professor at Hangzhou Normal University. Before that, I was a researcher in Internet Graphics Group, Microsoft Research Asia. I joined Microsoft Research Asia as an associate researcher in Oct. 2005. Before that, I have been a post-doc researcher at Ritsmeikan university in Japan. I received my Ph.D. Degree in Computer Graphics from Zhejiang University, Hangzhou, and my B.S. Degree and Master Degree in Computer Science from Hohai University in 1996 and 1999 respectively.  

 

Research Interests

Shape deformation, Computer Animation, Computational Geometry.

 

Professional Activities

Program Committee Member:

Pacific Graphics 2010

Paper Reviewer:

ACM SIGGRAPH, ACM SIGGRAPH Asia, IEEE Visualization, IEEE TVCG, SGP, Computers & Graphics

 

Publications

 

2012

 

Motion-Guided Mechanical Toy Modeling

Lifeng Zhu, Weiwei Xu, John Snyder, Yang Liu, Guoping Wang, Baining Guo

We introduce a new method to synthesize mechanical toys solely from the motion of their features. The designer specifies the geometry and a time-varying rotation and translation of each rigid feature component. Our algorithm automatically generates a mechanism assembly located in a box below the feature base that produces the specified motion. Parts in the assembly are selected from a parameterized set including belt-pulleys, gears, crank-sliders, quick-returns, and various cams (snail, ellipse, and double-ellipse). Positions and parameters for these parts are optimized to generate the specified motion, minimize a simple measure of complexity, and yield a well-distributed layout of parts over the driving axes. Our solution uses a special initialization procedure followed by simulated annealing to efficiently search the complex configuration space for an optimal assembly.

 

Conditionally accepted by ACM SIGGRAPH Asia 2012  [Paper] [Supplementary] [Video


 

 

An Interactive Approach to Semantic Modeling of Indoor Scenes with an RGBD Camera

Tianjia Shao, Weiwei Xu, Kun Zhou, Jingdong Wang, Dongping Li, Baining Guo

We present an interactive approach to semantic modeling of indoor scenes with a consumer-level RGBD camera. Using our approach, the user first takes a RGBD image of an indoor scene, which is automatically segmented into a set of regions with semantic labels. If the segmentation is not satisfactory, the user can draw some strokes to guide the algorithm to achieve better results. After the segmentation is finished, the depth data of each semantic region is used to retrieve a matching 3D model from a database. Each model is then transformed according to the image depth to yield the scene. For large scenes where a single image can only cover one part of the scene, the user can take multiple images to construct other parts of the scene. The 3D models built for all images are then transformed and unified into a complete scene. We demonstrate the efficiency and robustness of our approach by modeling several real-world scenes.

 

Conditionally accepted by ACM SIGGRAPH Asia 2012  [Paper] [Video] [Data


 

 

All-Hex Meshing using Singularity-Restricted Field

Yufei Li, Yang Liu, Weiwei Xu, Wenping Wang, Baining Guo

Decomposing a volume into high-quality hexahedral cells is a challenging task in geometric modeling and computational geometry. Inspired by the use of cross field in quad meshing and the CubeCover approach in hex meshing, we present a complete all-hex meshing framework based on singularity-restricted field that is essential to induce a valid all-hex structure. Given a volume represented by a tetrahedral mesh, we first compute a boundary-aligned 3D frame field inside it, then convert the frame field to be singularity-restricted by our effective topological operations. In our all-hex meshing framework, we present an enhanced CubeCover approach that reduces degenerate elements appearing in the volume parameterizations via tetrahedral split operations and handle flipped elements effectively in hex-mesh extraction. Experimental results show that our algorithm generates high-quality all-hex meshes from a variety of 3D volumes robustly and efficiently.

 

Conditionally accepted by ACM SIGGRAPH Asia 2012  [Paper] [Video


 

 

Diffusion Curve Textures for Resolution Independent Texture Mapping

Xin Sun, Guofu Xie, Yue Dong, Stephen Lin, Weiwei Xu, Wencheng Wang, Xin Tong, Baining GUo

We introduce a vector representation called diffusion curve tex-tures for mapping diffusion curve images (DCI) onto arbitrary surfaces. In contrast to the original implicit representation of DCIs [Orzan et al. 2008], where determining a single texture value requires iterative computation of the entire DCI via the Poisson equation, diffusion curve textures provide an explicit representa-tion from which the texture value at any point can be solved di-rectly, while preserving the compactness and resolution indepen-dence of diffusion curves. This is achieved through a formulation of the DCI diffusion process in terms of Green’s functions. This formulation furthermore allows the texture value of any rectangular region (e.g. pixel area) to be solved in closed form, which facilitates anti-aliasing. We develop a GPU algorithm that renders anti-aliased diffusion curve textures in real time, and demonstrate the effective-ness of this method through high quality renderings with detailed control curves and color variations.

 

ACM Transactions on Graphics (SIGGRAPH 2012)  [Paper][Video][bibtex


 

 

2011

 

General Planar Quadrilateral Mesh Design Using Conjugate Direction Field

Yang Liu, Weiwei Xu, Lifeng Zhu, Jun Wang, Baining Guo, Falai Chen, Guoping Wang

We present a novel method to approximate a freeform shape with a planar quadrilateral (PQ) mesh for modeling architectural glass structures. Our method is based on the study of conjugate direction fields (CDF) which allow the presence of k/4 singularities. Starting with a triangle discretization of a freeform shape, we first compute an as smooth as possible conjugate direction field satisfying the user’s directional and angular constraints, then apply mixed-integer quadrangulation and planarization techniques to generate a PQ mesh which approximates the input shape faithfully. We demonstrate that our method is effective and robust on various 3D models.

 

ACM SIGGRAPH Asia 2011  [Paper] [Video][bibtex


 

 

Discriminative Sketch-based 3D Model Retrieval via Robust Shape Matching

Tianjia Shao, Weiwei Xu, Kangkang Yin, Jingdong Wang, Kun Zhou, Baining Guo

We propose a sketch-based 3D shape retrieval system that is substantially more discriminative and robust than existing systems, especially for complex models. The power of our system comes from a combination of a contourbased 2D shape representation and a robust sampling-based shape matching scheme. They are defined over discriminative local features and applicable for partial sketches; robust to noise and distortions in hand drawings; and consistent when strokes are added progressively. However, our robust shape matching algorithm requires dense sampling and registration, which incurs a high computational cost. We thus devise critical acceleration methods to achieve interactive performance: precomputing kNN graphs that record transformations between neighboring contour images and enable fast online shape alignment; pruning sampling and shape registration strategically and hierarchically; and parallelizing shape matching on multi-core platforms or GPUs. We demonstrate the effectiveness of our system through various experiments, comparisons, and a user study.

 

Computer Graphics Forum (PG 2011)  [Paper] [Video][Bibtex


 

 

2010

 

Sampling-based Contact-Rich Motion Control

Libin Liu, KangKang Yin, Michiel van de Panne, Tianjia Shao, Weiwei Xu

Human motions are the product of internal and external forces, but these forces are very difficult to measure in a general setting. Given a motion capture trajectory, we propose a method to reconstruct its open-loop control and the implicit contact forces. The method employs a strategy based on randomized sampling of the control within user-specified bounds, coupled with forward dynamics simulation. Sampling-based techniques are well suited to this task because of their lack of dependence on derivatives, which are difficult to estimate in contact-rich scenarios. They are also easy to parallelize, which we exploit in our implementation on a compute cluster. We demonstrate reconstruction of a diverse set of captured motions, including walking, running, and contact rich tasks such as rolls and kip-up jumps. We further show how the method can be applied to physically based motion transformation and retargeting, physically plausible motion variations, and reference trajectory-free idling motions. Alongside the successes, we point out a number of limitations and directions for future work.

 

ACM SIGGRAPH 2010  [Paper] [Video 46MB][Bibtex


 

 

Deformation Transfer to Multi-component Objects

Kunzhou, Weiwei Xu, Yiying Tong, Mathieu Desbrun

We present a simple and effective algorithm to transfer deformation between surface meshes with multiple components. The algorithm automatically computes spatial relationships between components of the target object, builds correspondences between source and target, and finally transfers deformation of the source onto the target while preserving cohesion between the target’s components. We demonstrate the versatility of our approach on various complex models.

Computer Graphics Forum (Eurographics 2010) [Paper] [Video 22MB][Bibtex

 

 

 

2009

 

Joint-aware Manipulation of Deformable Model

Weiwei Xu, Jun Wang, KangKang Yin, Kun Zhou, Michiel van de Panne, Falai Chen, Baining Guo

 

Complex mesh models of man-made objects often consist of multiple components connected by various types of joints. We propose a joint-aware deformation framework that supports the direct manipulation of an arbitrary mix of rigid and deformable components. We apply slippable motion analysis to automatically detect multiple types of joint constraints that are implicit in model geometry. For single-component geometry or models with disconnected components, we support user-defined virtual joints. We integrate manipulation handle constraints, multiple components, joint constraints, joint limits, and deformation energies into a single volumetric-cell based space deformation problem. An iterative, parallelized Gauss-Newton solver is used to solve the resulting non-linear optimization. Interactive deformable manipulation is demonstrated on a variety of geometric models while automatically respecting their multi-component nature and the natural behavior of their joints.

ACM SIGGRAPH 2009, [Paper] [Video 66MB][Bibtex]

 

 

 

2008

 

Keyframe-based Video Object Deformation

Yanlin Weng, Weiwei Xu, Shichao Hu, Jun Zhang, Baining Guo

 

This paper presents a novel deformation system for video objects. The system is designed to minimize the amount of user interaction, while providing flexible and precise user control. It has a keyframe-based user interface. The user only needs to manipulate the video object at some keyframes. Our algorithm will smoothly propagate the editing result from the keyframes to the rest frames and automatically generate the new video object. The algorithm is able to preserve the temporal coherence as well as the shape features of the video objects in the original video clips.

IEEE Cyber World 2008, [Paper] [Video 32MB][Bibtex]

 

2007

 

Gradient Domain Editing of Deforming Mesh Sequence

Weiwei Xu, Kun Zhou, Yizhou Yu, Qifeng Tan, Qunsheng Peng, Baining Guo.

 

Many graphics applications, including computer games and 3D animated films, make heavy use of deforming mesh sequences. In this paper, we generalize gradient domain editing to deforming mesh sequences. Our framework is keyframe based. Given sparse and irregularly distributed constraints at unevenly spaced keyframes, our solution first adjusts the meshes at the keyframes to satisfy these constraints, and then smoothly propagate the constraints and deformations at keyframes to the whole sequence to generate new deforming mesh sequence. To achieve convenient keyframe editing, we have developed an efficient alternating least-squares method. It harnesses the power of subspace deformation and two-pass linear methods to achieve high-quality deformations. We have also developed an effective algorithm to define boundary conditions for all frames using handle trajectory editing. Our deforming mesh editing framework has been successfully applied to a number of editing scenarios with increasing complexity, including footprint editing, path editing, temporal filtering, handle-based deformation mixing, and spacetime morphing.

ACM Transactions on Graphics (SIGGRAPH 2007) [Paper] [Video 80MB][Bibtex]

Direct Manipulation of Subdivision Mesh

Kun Zhou, Xin Huang, Weiwei Xu, Baining Guo.

 

We present an algorithm for interactive deformation of subdivision surfaces, including displaced subdivision surfaces and subdivision surfaces with geometric textures. Our system lets the user directly manipulate the surface using freely-selected surface points as handles. During deformation the control mesh vertices are automatically adjusted such that the deforming surface satisfies the handle position constraints while preserving the original surface shape and details. To best preserve surface details, we develop a gradient domain technique that incorporates the handle position constraints and detail preserving objectives into the deformation energy. For displaced subdivision surfaces and surfaces with geometric textures, the deformation energy is highly nonlinear and cannot be handled with existing iterative solvers. To address this issue, we introduce a shell deformation solver, which replaces each numerically unstable iteration step with two stable mesh deformation operations. Our deformation algorithm only uses local operations and is thus suitable for GPU implementation. The result is a real-time deformation system running orders of magnitude faster than the state-of-the-art multigrid mesh deformation solver. We demonstrate our technique with a variety of examples, including examples of creating visually pleasing character animations in real-time by driving a subdivision surface with motion capture data.

 

ACM Transactions on Graphics (SIGGRAPH 2007) [Paper] [Video 80MB][Bibtex]

 

 

 

 

 

 

2003~2010

 

Gradient Domain Mesh Deformation – A Survey

Weiwei Xu, Kun Zhou

Journal of Computer Science and Technology, 24(1):6-18, 2009

 

 

 

2D Shape Deformation using Nonlinear Least Squares Optimization

Yanlin Weng, Weiwei Xu, Kun Zhou, Baining Guo

The visual Computer, 22(9-11):653-660, 2006, [Paper 2MB]

 

 

Footprint Sampling based Motion Editing

Weiwei Xu, Zhigeng Pan, Mingmin Zhang

Int. J. Image Graphics 3(2): 311-324 (2003)

 

 

Easybowling: a small bowling machine based on virtual simulation

Zhigeng Pan, Weiwei Xu, Jin Huang, Mingmin Zhang, Jiaoying Shi

Computers & Graphics 27(2): 231-238 (2003)

 

 

 

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