Note: The materials presented below are for academic use only. Copyright and all rights therein are retained by the authors or by the respective copyright holders.
(Full Publication List; Entry@DBLP)
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Hoi Sheung, and Charlie C.L. Wang, "Robust mesh reconstruction from unoriented noisy points",
ACM Symposium on Solid and Physical Modeling 2009, pp.13-24, San Francisco, California, October 5-8, 2009. [PDF] (Back Cover Image of Proceeding)
Abstract We present a robust method to generate mesh surfaces from unoriented noisy points in this paper. The whole procedure consists of three steps. Firstly, the normal vectors at points are evaluated by a highly robust estimator which can fit surface corresponding to less than half of the data points and fit data with multi-structures. This benefits us with the ability to well reconstruct the normal vectors around sharp edges and corners. Meanwhile, clean point cloud equipped with piecewise normal is obtained by projecting points according to the robust fitting. Secondly, an error-minimized subsampling is applied to generate a wellsampled point cloud. Thirdly, a combinational approach is employed to reconstruct a triangular mesh connecting the down-sampled points, and a polygonal mesh which preserves sharp features is constructed by the dual-graph of triangular mesh. Parallelization method of the algorithm on a consumer PC using the architecture of GPU is also given. |
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Charlie C.L. Wang, Yunbo Zhang, and Hoi Sheung, "From styling design to products fabricated by planar materials", IEEE Computer Graphics and Application, accepted with minor revision.
[From Styling Design to Fabricated Wetsuit - WMV (13MB)]
Abstract This article describes a geometric modeling system that generates industry required planar pieces for fabricating user-customized products from styling designs. The processing from style design to industrial patterns is automated. Prestored styling designs can be automatically mapped into different reference model shapes and then unfolded into planar pieces. Besides, a map-guided algorithm has been developed to locate unfolded pieces according to industrial requirement. |
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Charlie C.L. Wang,
"A note on least-norm solution of global WireWarping",
Computer-Aided Design, vol.41, no.9, pp.695-698, September 2009.
[PDF]
Abstract WireWarping is a fast surface flattening approach which presents a very important property of length-preservation on feature curves. The global scheme of WireWarping formulates the warping problem into an optimization in angle space and solves it by the Newton's method. However, some diverged examples were found in our recent tests. This technical note presents a least-norm solution in terms of angle-error for the global WireWarping. The experimental tests show that the least-norm solution is more robust than the Newton's algorithm. |
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Charlie C.L. Wang, and Kai Tang, "Pattern computation for compression garment by a physical/geometric approach",
Computer-Aided Design, accepted.
[PDF]
(This is an extended version of the paper - Pattern computation for compression garment, which is published in ACM Symposium on Solid and Physical Modeling 2008, pp.203-211, Stony Brook, New York, USA, June 2-4, 2008.) Abstract This paper addresses the problem of computing planar patterns for compression garments. In the garment industry, the compression garment has been more and more widely used to retain a shape of human body, where certain strain (or normal pressure) is designed at some places on the compression garment. Variant values and distribution of strain can only be generated by sewing different 2D patterns and warping them onto the body. We present a physical/geometric approach for computing 2D meshes that, when folded onto the 3D body, can generate a user-defined strain distribution through proper distortion. This is opposite to the widely studied mesh parameterization problem, whose objective is to minimize the distortion between the 2D and 3D meshes in angle, area or length. |
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Hanli Zhao, Ran Fan, Charlie C.L. Wang, Xiaogang Jin, Yuwei Meng, "Fireworks controller",
Computer Animation and Virtual Worlds, Special Issue of International Conference on Computer Animation and Social Agents 2009, vol.20, no.2-3, pp.185-194, June 2009.
[Video]
Abstract This paper presents the fireworks controller, a novel real-time shape-constrained fireworks animation system. We depict the shape of a firework by a 3D mesh. In order to approximate the mesh using evenly distributed points, we propose a fast point sampling method by extending the dual depth peeling algorithm. The samples are then taken as input to shape-constrained fireworks whose physically plausible animations are based on inverse dynamics. We present a highly parallel iterative clustering algorithm to support multi-level fireworks explosion. In order to simulate natural fuzzy fireworks, we impose extra random particles with a parallel random number generator. Experimental results demonstrate the prettiness and efficiency of the proposed approach. |
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Shengjun Liu, and Charlie C.L. Wang, "Duplex fitting of zero-level and offset surfaces", Computer-Aided Design, vol.41, no.4, pp.268-281, April 2009.
[PDF]
Abstract Offset surfaces play an important role in various CAD/CAM applications. Given a set of oriented points, we propose a hierarchical method in this paper to fit both the zero-level surface and its offset surface with a single implicit function. The implicit function is formed by compactly supported radial basis functions (CSRBFs). Different from other existing methods in literature, our approach reconstructs an implicit function which interpolates or approximates both the zero-level surface and the offset surface of a given point set simultaneously. Employing locally supported functions leads to an efficient computational procedure, while the coarse-to-fine hierarchy makes our approach insensitive to the density of scattered data and allows us to reconstruct large parts of missing data. The performance of our method is demonstrated by a number of examples and the application of adaptive slicing hollowed models in rapid prototyping. |
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Yong Chen, and Charlie C.L. Wang, "Layered Depth-Normal Images for complex geometries - part one: accurate sampling and adaptive modeling", ASME IDETC/CIE 2008 Conference, 28th Computers and Information in Engineering Conference, New York City, New York, August 3-6, 2008. (Best Paper Award)
[PDF]
Abstract The layered depth-normal images (LDNIs) is an implicit representation of solid models that sparsely encodes the shape boundary in three orthogonal directions. We present a LDNI-based geometric modeling method for applications with high accuracy requirements. In our method, we first construct LDNIs models from input polygonal models. The accuracy of the generated LDNIs models can be controlled by setting pixel width during the construction process. Even for very complex geometries and high accuracy requirements, the construction process is fast with the aid of graphics hardware. Based on the LDNIs models, we then perform geometric modeling operations. Two types of operations are presented including regularizing and Boolean operations. The geometric modeling operations are straightforward and easy to be implemented robustly. From the processed LDNIs model, an adaptive sampling method is presented to construct a cell representation that includes both uniform and octree cells. Finally 2-manifold polygonal mesh surfaces are constructed from the cell representation. For high accuracy requirements that are typical in CAD/CAM applications, we present a volume tiling technique and a parallel implementation to accelerate the computation. Our method achieves a good balance between the accuracy and computational resources. We report experimental results on a variety of CAD models. The results demonstrate the effectiveness and efficiency of our approach especially for modeling complex geometries. |
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Charlie C.L. Wang, and Yong Chen, "Layered Depth-Normal Images for complex geometries - part two: manifold-preserved adaptive contouring", ASME IDETC/CIE 2008 Conference, 28th Computers and Information in Engineering Conference, New York City, New York, August 3-6, 2008.
[PDF]
Abstract We present an adaptive contouring approach to generate contour surface from solid models represented by Layered Depth-Normal Images (LDNI) sampled in three orthogonal directions. Our contouring algorithm builds an octree structure for mesh generation in a top-down manner: starting from the bounding box of a LDNI solid model, the cells are recursively subdivided into smaller sub-cells based on the topology and geometry criteria of refinement until both of the requirements, the topology in cell is simple and the geometry approximation error is less than a user defined tolerance, are satisfied. The subdivision also stops when the processed cells reach the finest resolution of LDNI models. In order to overcome the topology ambiguity inside a cell that leads to the occurrence of non-manifold entities, we analyze the possible inside/outside configurations of cell-nodes and exploit two strategies to generate manifold-preserved mesh surfaces. Moreover, the most time-consuming step of our contouring algorithm ¨C the construction of octree structure can be easily parallelized to run under a computer framework with multiple-processors and shared memory. Several examples have been tested in the paper to demonstrate the success of our method. |
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Xiaogang Jin, Jiayi Xu, Charlie C.L. Wang, Shengsheng Huang, and Jun Zhang,
"Interactive control of large-crowd navigation in virtual environment using vector field",
IEEE Computer Graphics and Application, vol.28, no.6, pp.37-46, November/December 2008.
[PDF]
[Video]
(This is an extended version of the paper - Interactive control of real-time crowd navigation in virtual environment, which is published in ACM Symposium on Virtual Reality Software and Technology 2007, Newport Beach, California, November 5-7, 2007. (Back Cover Image of Proceeding)) Abstract Providing interactive control is a hot topic in the research of crowd navigation. In this paper, we propose a simple but effective way for authoring crowd scene. The movement of each pedestrian is composed of an autonomous part and a user specified one, the ratio between them can be interactively adjusted. The governed part is realized by Radial Basis Functions (RBF) based vector fields. With this governing tool, users can easily drive the flow of crowds by sketching velocities on anchor points in the scene. Our approach is fast enough to allow on-the-fly modification of vector fields. |
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Charlie C.L. Wang,
"Extracting manifold and feature-enhanced mesh surfaces from binary volumes",
ASME Journal of Computing and Information Science in Engineering, vol.8, no.3, 2008. [PDF]
Abstract This paper presents an approach to automatically recover mesh surfaces with sharp-edges for solids from their binary volumetric discretizations (i.e., voxel models). Our method consists of three steps. The topology singularity is first eliminated on the binary grids so that a topology correct mesh M0 can be easily constructed. After that, the shape of M0 is refined and its connectivity is iteratively optimized into Mn. The shape refinement is governed by the duplex distance-fields derived from the input binary volume model. However, the refined mesh surface lacks sharp edges. Therefore, we employ an error-controlled variational shape approximation (VSA) algorithm to segment Mn into nearly planar patches, and then recover sharp edges by applying a novel segmentation-enhanced bilateral filter to the surface. Using the technique presented in this paper, smooth regions and sharp edges can be automatically recovered from raw binary volume models without scalar field or Hermite data. Comparing to other related surface recovering methods on binary volume, our algorithm needs less heuristic coefficients. |
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Chuan Zhou, Xiaogang Jin, and Charlie C.L. Wang,
"Shear buckling and dynamic bending in cloth simulation",
Computer Animation and Virtual Worlds, Special Issue of International Conference on Computer Animation and Social Agents 2008, vol.19, no.3-4, pp.493-503, August 2008.
[Video]
Abstract This paper addresses the problem of simulating the mechanical behavior of cloth in computer animation, which is very important and challenging. The micro-structure of woven fabrics leads to significantly different shear reaction from other sheet materials, which has been neglected in previous approaches of cloth simulation. Therefore, it is beneficial for cloth simulation to model the shear buckling and structural bending separately. We analyze the shear buckling yielded by the micro-structure of woven and the dynamic bending based on the thin-shell theory, and develop a compact implementation of the new model on mass-spring systems. Experimental results show that the animations generated using this technique are with wrinkles and folds appearing and vanishing in a more natural way than other approaches. |
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Chuan Zhou, Xiaogang Jin, and Charlie C.L. Wang,
"Efficient and stable simulation of cloth undergoing large rotations",
Computing in Science & Engineering, IEEE Computer Society and American Institute of Physics, vol.10, no.4, pp.30-40, 2008.
Abstract The semi-implicit integration scheme has been employed in cloth animation in recent years because of its high stability and efficiency. However, it will give notable vibrations on the mass-spring system because of the linear approximation on large rotations, which does always occur in the cloth simulation. Hence, the simulation suffers inaccuracy and inefficiency so that the number of iterations increases enormously and vibrates significantly in adjacent time steps. Unrealistic results are given on the large rotating surface regions. In this paper, we propose a novel physical model which is stable and efficient when simulating clothes with large rotation. Furthermore, our approach introduces less artificial damping effects than the previously proposed semi-implicit methods. |
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Chih-Hsing Chu, Charlie C.L. Wang, and Chi-Rung Tsai,
"Computer aided geometric design of strip using developable Bezier patches",
Computers in Industry, vol.59, no.6, pp.601-611, 2008. [PDF]
Abstract Developable strip is commonly used in product design due to its ease of manufacture. This paper proposes an algorithm for geometric design of strip using developable Bezier patches. It computes an aggregate of triangular and quadrilateral patches interpolate two given space curves defining a strip. The computation process selects optimal solutions in terms of surface assessment criteria specified by the user. Each patch is then degree-elevated to gain extra degrees of freedom, which produce G1 across the patch boundaries by modifying the control points while preserving the surface developability. Test examples with different design parameters illustrate and validate the feasibility of the proposed algorithm. In comparison with previous studies, this work allows strip design with freeform developable patches, generates better results in the surface assessment, and provides more flexible control on the design shape. It serves as a simple but effective approach for computer aided geometric design of developable strip. |
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Juncong Lin, Xiaogang Jin, Charlie C.L. Wang, and Kin-Chuen Hui,
"Mesh composition on models with arbitrary boundary topology",
IEEE Transactions on Visualization and Computer Graphics, vol.14, no.3, pp.653-665, May/June, 2008.
[PDF]
[Video]
Abstract This paper presents a new approach for the mesh composition on models with arbitrary boundary topology. After cutting the needed parts from existing mesh models and putting them into the right pose, an implicit surface is adopted to smoothly interpolate the boundaries of models under composition. An interface is developed to control the shape of the implicit transient surface by using sketches to specify the expected silhouettes. After that, a localized Marching Cubes algorithm is investigated to tessellate the implicit transient surface so that the mesh surface of composed model is generated. Different from existing approaches in which the models under composition are required to have pairwise merging boundaries, the framework developed based on our techniques have the new function to fuse models with arbitrary boundary topology. |
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Charlie C.L. Wang,
"WireWarping: A fast surface flattening approach with length-preserved feature curves",
Computer-Aided Design, vol.40, no.3, pp.381-395, 2008.
[PDF]
Abstract This paper presents a novel approach - WireWarping for computing a flattened planar piece with length-preserved feature curves from a 3D piecewise linear surface patch. The property of length-preservation on feature curves is very important to industrial applications for controlling the shape and dimension of products fabricated from planar pieces. WireWarping simulates warping a given 3D surface patch onto plane with the feature curves as tendon wires to preserve the length of their edges. During warping, the surface-angle variations between edges on wires are minimized so that the shape of a planar piece is similar to its corresponding 3D patch. Two schemes - the progressive warping and the global warping schemes are developed, where the progressive scheme is flexible for local shape control and the global scheme gives good performance on highly distorted patches. Experimental results show that WireWarping can successfully flatten surface patches into planar pieces while preserving the length of edges on feature curves. |
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Charlie C.L. Wang,
"A least-norm approach to flattenable mesh surface processing",
IEEE International Conference on Shape Modeling and Applications 2008,
pp.131-138, Stony Brook, New York, USA, June 4-6, 2008. [PDF]
Abstract Following the definition of developable surface in differential geometry, the flattenable mesh surface, a special type of piecewise-linear surface, inherits the good property of developable surface about having an isometric map from its 3D shape to a corresponding planar region. Different from the developable surfaces, a flattenable mesh surface is more flexible to model the objects with complex shapes (e.g., the cramped paper or the warped leather with wrinkles). Modelling a flattenable mesh from a given input mesh surface can be solved under a constrained nonlinear optimization framework. In this paper, we reformulate the problem in terms of estimation error. Therefore, the shape of a flattenable mesh can be computed by the least-norm solutions in a faster speed. Moreover, the method by adding shape constraints to the modelling of flattenable mesh surfaces has been exploited. We show that the proposed method can compute flattenable mesh surfaces from input piecewise linear surfaces successfully and efficiently. |
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Charlie C.L. Wang,
"Flattenable mesh surface fitting on boundary curves",
ASME Journal of Computing and Information Science in Engineering, vol.8, no.2, 2008.
[PDF]
Abstract This paper addresses the problem of fitting flattenable mesh surfaces in R³ onto piecewise linear boundary curves, where a flattenable mesh surface inherits the isometric mapping to a planar region in R². The developable surface in differential geometry shows the nice property. However, it is difficult to fit developable surfaces to a boundary with complex shape. The technique presented in this paper can model a piecewise linear flattenable surface that interpolates the given boundary curve and approximates the cross-tangent normal vectors on the boundary. At first, an optimal planar polygonal region is computed from the given boundary curve B in R³, triangulated into a planar mesh surface, and warped into a mesh surface in R³ satisfying the continuities defined on B. Then, the fitted mesh surface is further optimized into a Flattenable Laplacian (FL) mesh which preserves the positional continuity and minimizes the variation of cross-tangential normals. Assembled set of such FL mesh patches can be employed to model complex products fabricated from sheets without stretching. |
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Charlie C.L. Wang,
"Towards flattenable mesh surfaces", Computer-Aided Design, vol.40, no.1, pp.109-122, 2008.
[PDF]
Abstract In many industries, products are constructed by assembled surface patches in R³, where each patch is expected to have an isometric map to a corresponding region in R². The widely investigated developable surfaces in differential geometry show this property. However, the method to model a piecewise-linear surface with this characteristic is still under research. To distinguish from the continuous developable surface, we name them as flattenable mesh surfaces since a polygonal mesh has the isometric mapping property if it can be flattened into a two-dimensional sheet without stretching. In this paper, a novel flattenable mesh surface (Flattenable Laplacian mesh) is introduced and the relevant modelling tool is formulated. Moreover, for a given triangular mesh which is almost flattenable, a local perturbation approach is developed to improve its flattenability. The interference between the meshes under process and their nearby objects has been prevented in this local flattenable perturbation. Both the computations of Flattenable Laplacian meshes and the flattenable perturbation are based on the constrained optimization technology. |
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Charlie C.L. Wang,
"Computing length-preserved free boundary for quasi-developable mesh segmentation",
IEEE Transactions on Visualization and Computer Graphics, vol.14, no.1, pp.25-36, Jan/Feb, 2008.
[PDF] [Supplementary]
Abstract Stretch-free surface flattening has been requested by a variety of applications. At present, the most difficult problem is how to segment a given model into nearly developable atlases so that a nearly stretch-free flattening can be computed. The criterion for segmentation is needed to evaluate the possibility of flattening a given surface patch, which should be fast computed. In this paper, we present a method to compute the length-preserved free boundary (LPFB) of a mesh patch which speeds up the mesh parameterization. The distortion on parameterization can then be employed as the criterion in a trial-and-error algorithm for segmenting a given model into nearly developable atlases. The computation of LPFB is formulated as a numerical optimization problem in the angle space, where we are trying to optimize the angle excesses on the boundary while preserving the constraints derived from the closed-path theorem and the length preservation. |
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Shengjun Liu, Charlie C.L. Wang, Kin-Chuen Hui, Xiaogang Jin, and Hanli Zhao,
"Ellipsoid-tree construction for solid objects",
Proceedings of ACM Symposium on Solid and Physical Modeling 2007, pp.303-308, Beijing, China, June 4-6, 2007.
[PDF]
Abstract As ellipsoids have been employed in the collision handling of many applications in physical simulation and robotics systems, we present a novel algorithm for generating a bounding volume hierarchy (BVH) from a given model with ellipsoids as primitives. Our algorithm approximates the given model by a hierarchical set of optimized bounding ellipsoids. The ellipsoid-tree is constructed by a top-down splitting. Starting from the root of hierarchy, the volume occupied by a given model is divided into k sub-volumes where each is approximated by a volume bounding ellipsoid. Recursively, each sub-volume is then subdivided into ellipsoids for the next level in the hierarchy. The k ellipsoids at each hierarchy level for a sub-volume bounding is generated by a bottom-up algorithm - simply, the sub-volume is initially approximated by m spheres (m >> k), which will be iteratively merged into k volume bounding ellipsoids and globally optimized to minimize the approximation error. Benefited from the anisotropic shape of primitives, the ellipsoid-tree constructed in our approach gives tighter volume bound and higher shape fidelity than another widely used BVH, sphere-tree. |
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Shengjun Liu, Xiaogang Jin, Charlie C.L. Wang, and Kin-Chuen Hui,
"Ellipsoidal-blob approximation of 3D models and its applications", Computers & Graphics, vol.31, no.2, pp.243-251, 2007.
[PDF]
[Animation]
Abstract This paper presents a technique for automatically approximating a given mesh model with an ellipsoidal blobby model. Firstly, an ellipsoid decomposition algorithm is introduced to approximate given models by ellipsoids. After that, a blobby implicit surface employing ellipsoidal blobs is modeled to fit the sampling points on the given mesh. Finally, the reconstructed ellipsoidal blobby model is applied in two applications: the geometry data reduction and the target shape controlled cloud animation. |
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Min Li, Shuming Gao, and Charlie C.L. Wang,
"Real-time collaborative design with heterogeneous CAD systems based on neutral modeling commands",
ASME Journal of Computing and Information Science in Engineering, vol.7, no.2, pp.113-125, 2007.
[PDF]
Abstract This paper presents an integration-based solution for developing a real-time collaborative design platform on heterogeneous CAD systems. Different from the visualization-based approaches, the product models under design are allowed to be constructed and be modified from various sites together in the proposed collaborative design platform. Our approach is based on a mechanism for the translation between system modeling operations (SMO) and neutral modeling commands (NMC). Every operation given by a user on one site is translated into a NMC and transmitted to all the other sites through network, and then the received NMC is converted into corresponding SMOs on every other site instantaneously. Since only the commands but not the product data are transferred, the data size under transmission is greatly reduced - so that a real-time synchronization can be achieved with a standard bandwidth. In addition, by developing system-dependent NMC-SMO translators on different client CAD systems, users on different sites could join the collaboration by using their familiar CAD systems; this is the benefit that cannot be offered by the homogeneous co-design systems. The prototype implementation proves that our approach works well for integrating various current popular commercial CAD/CAM systems into a real-time collaborative design platform. |
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Charlie C.L. Wang, and Kai Tang,
"Woven model based geometric design of elastic medical braces", Computer-Aided Design, vol.39, no.1, pp.69-79, 2007.
[PDF]
Abstract This paper presents an algorithm for automatically computing the planar patterns of custom-made assistive medical braces, which are employed to restrict the motion of the joints (such as wrist and knee) that suffer from musculoskeletal disorders caused by repetitive strain injuries. An elastic brace is manufactured by warping a planar elastic fabric pattern. With a specified material, different shapes of planar patterns for producing a brace will generate different biomechanical effects on the joint. As an assistive medical device, an elastic brace is often requested to provide certain normal pressures at certain specific locations on the joint. Traditionally the planar pattern of a brace respecting the prescribed normal pressure requirement is designed through empirical tests by trial-and-error. We develop a woven fitting based method in this paper to automate this geometric design process. |
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Charlie C.L. Wang,
"Direct extraction of surface meshes from implicitly represented heterogeneous volumes", Computer-Aided Design, vol.39, no.1, pp.35-50, 2007.
[PDF]
Abstract This paper describes a novel algorithm to extract surface meshes directly from implicitly represented heterogeneous models made of different constituent materials. Our approach can directly convert implicitly represented heterogeneous objects into a surface model separating homogeneous material regions, where every homogeneous region in a heterogeneous structure is enclosed by a set of two-manifold surface meshes. Unlike other discretization techniques of implicitly represented heterogeneous objects, the intermediate surfaces between two constituent materials can be directly extracted by our algorithm. Therefore, it is more convenient to adopt the surface meshes from our approach in the boundary element method (BEM) or as a starting model to generate volumetric meshes preserving intermediate surfaces for the finite element method (FEM). The algorithm consists of three major steps: firstly, a set of assembled two-manifold surface patches coarsely approximating the interfaces between homogeneous regions are extracted and segmented; secondly, signed distance-fields are constructed that each field expresses the Euclidean distance from points to the surface of one homogeneous material region; and finally, coarse patches generated in the first step is dynamically optimized to give adaptive and high-quality surface meshes. The manifold topology is preserved on each surface patch. |
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Jianbing Shen, Xiaogang Jin, Chuan Zhou, and Charlie C.L. Wang,
"Gradient based image completion by solving Poisson equation", Computers & Graphics, vol.31, no.1, pp.119-126, 2007.
[PDF]
Abstract This paper presents a novel gradient-based image completion algorithm for removing significant objects from natural images or photographs. Our method reconstructs the region of removal in two phases. Firstly, the gradient maps in the removed area are completed through a patch based filling algorithm. After that, the image is reconstructed from the gradient maps by solving a Poisson equation. A new patch-matching criterion is developed in our approach to govern the completed of gradient maps. Both the gradient and the color information are incorporated in this new criterion, so a better image completion result is obtained. Several examples and comparisons are given at the end of the paper to demonstrate the performance of our gradient-based image completion approach. |
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Charlie C.L. Wang, Kin-Chuen Hui, and K.M. Tong,
"Volume parameterization for design automation of customized free-form products",
IEEE Transactions on Automation Science and Engineering, vol.4, no.1, pp.11-21, 2007.
[PDF]
Abstract This paper addresses the problem of volume parameterization that serves as the geometric kernel for design automation of customized free-form products. The purpose of volume parameterization is to establish a mapping between the spaces near to two reference free-form models, so that the shape of a product presented in free-form surfaces can be transferred from the space around one reference model to another reference models. The mapping is expected to keep the spatial relationship between the product model and reference models as much as possible. We separate the mapping into rigid body transformation and elastic warping. The rigid body transformation is determined by anchor points defined on the reference models using a least-square fitting approach. The elastic warping function is more difficult to obtained, especially when the meshes of the reference objects are inconsistent. A three-stage approach is conducted. Firstly, a coarse-level warping function is computed based on the anchor points. In the second phase, the topology consistency is maintained through a surface fitting process. Finally, the mapping of volume parameterization is established on the surface fitting result. Comparing to previous methods, the approach presented here is more efficient. Also, benefited from the separation of rigid body transformation and elastic warping, the transient shape of a transferred product does not give unexpected distortion. At the end of this paper, various industry applications of our approach in design automation are demonstrated. |
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Shengjun Liu, Xiaogang Jin, Charlie C.L. Wang, and Jim X. Chen,
"Animation of water waves on mesh surfaces",
Computing in Science & Engineering, IEEE Computer Society and American Institute of Physics, vol.8, no.5, pp.81-87, Sept/Oct, 2006.
[Errata]
[Movie]
Abstract This article proposes a practical approach for simulating the phenomenon of water waves on 3D mesh surfaces. First of all, the geodesic distance map, which will govern the movement of water waves in the simulation, is computed on a given mesh surface. Based on the geodesic distance map, we then simulate the water waves on 3D surfaces using a sinusoidal wave model with damping. Our computing method for the geodesic distance map can process the scenario with multiple sources. Together with the method for superposing multiple water waves, the water waves with various sources can be simulated on the surface of a given mesh model. To demonstrate the performance of our approach, example animations are generated at the end of the paper - all can be updated in an interactive frame rate. |
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Charlie C.L. Wang,
"Bilateral recovering of sharp edges on feature-insensitive sampled meshes",
IEEE Transactions on Visualization and Computer Graphics, vol.12, no.4, pp.629-639, Jul/Aug, 2006.
[PDF]
Abstract A variety of computer graphics applications sample surfaces of 3D shapes in a regular grid without making the sampling rate adaptive to the surface curvature or sharp features. Triangular meshes that interpolate or approximate these samples usually exhibit relative big error around the insensitive sampled sharp features. This paper presents a robust approach conducting bilateral filters to recover sharp edges on such insensitive sampled triangular meshes. Motivated by the impressive results of bilateral filtering for mesh smoothing and denoising, we adopt it to govern the sharpening of triangular meshes. After recognizing the regions that embed sharp features, we recover the sharpness geometry through bilateral filtering, followed by iteratively modifying the given mesh's connectivity to form single-wide sharp edges that can be easily detected by their dihedral angles. We show that the proposed method can robustly reconstruct sharp edges on feature-insensitive sampled meshes. |
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Charlie C.L. Wang,
"Incremental reconstruction of sharp edges on mesh surfaces",
Computer-Aided Design, vol.38, no.6, pp.689-702, 2006.
[PDF]
Abstract Limited by the regular grids in computing, many modelling approaches (e.g., field-based methods) sample 3D shape insensitive to sharp features therefore exhibit aliasing errors, by which a lot of sharp edges and corners are lost on the reconstructed surface. An incremental approach for recovering sharp edges on an insensitive sampled triangular mesh is presented in this paper, so that shape approximation errors are greatly reduced. Either chamfered or blended sharp edges on an input triangular mesh could be successfully reconstructed by the signals inherent in the mesh. As a non-iterative method, our approach could be finished in a very short time comparing to those diffusion-based sharp-feature reproducers. The region embedding sharp features is first identified through normal variations. The positions of vertices in the sharp-feature embedded region are then predicted progressively from outer to the inner of sharp regions so that sharp edges could be recovered in the sense of region shrinking. |
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Yu Wang, Charlie C.L. Wang, and Matthew M.F. Yuen,
"Duplicate-skins for compatible mesh modelling",
Proceedings of ACM Symposium on Solid and Physical Modeling 2006, pp.207-217, Cardiff University, Wales, UK, June 6-8, 2006.
[PDF]
Abstract As compatible meshes play important roles in many computer-aided design applications, we present a new approach for modelling compatible meshes. Our compatible mesh modelling method is derived from the skin algorithm [Markosian et al. 1999] which conducts an active particle-based mesh surface to approximate the given models serving as skeletons. To construct compatible meshes, we developed a duplicate-skins algorithm to simultaneously grow two skins with identical connectivity over two skeleton models; therefore, the resultant skin meshes are compatible. Our duplicateskins algorithm has less topological constraints on the input models: multiple polygonal models, models with ill-topology meshes, or even point clouds could all be employed as skeletons to model compatible meshes. Based on the results of our duplicate-skins algorithm, the modelling method of n-Ary compatible meshes is also developed in this paper. |
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Xiaogang Jin, Juncong Lin, Charlie C.L. Wang, Jieqing Feng, and Hanqiu Sun,
"Mesh fusion using functional blending on topologically incompatible sections",
The Visual Computer, vol.22, no.4, pp.266-275, 2006.
[PDF]
Abstract Three-dimensional mesh fusion provides an easy and fast way to create new mesh models from existing ones. We introduce a novel approach of mesh fusion in this paper based on functional blending. Our method has no restriction of disk-like topology or one-ring opening on the meshes to be merged. First of all, the sections with boundaries of the under-fusing meshes are converted into implicit representations. An implicit transition surface, which joins the sections together while keeping smoothness at the boundaries, is then created based on cubic Hermite functional blending. Finally, the implicit surface is tessellated to form resultant mesh. Our scheme is both efficient and simple, with which users can easily construct complex 3D interesting models. |
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Kai Tang, Charlie C.L. Wang, and Danny Z. Chen,
"Minimum area convex packing of two convex polygons",
International Journal of Computational Geometry and Applications, vol.16, no.1, pp.41-74, 2006.
[PDF]
Abstract Given two convex polygons P and Q in the plane that are free to translate and rotate, a convex packing of them is the convex hull of a placement of P and a placement of Q whose interiors do not intersect. A minimum area convex packing of P and Q is one whose area is minimized. The problem of designing a deterministic algorithm for finding a minimum area convex packing of two convex polygons has remained open. We address this problem by first studying the contact configurations between P and Q and their algebraic structures. Crucial geometric and algebraic properties on the area function are then derived and analyzed which enable us to successfully discretize the search space. This discretization, together with a delicate algorithmic design and careful complexity analysis, allows us to develop an efficient O((n+m)nm) time deterministic algorithm for finding a true minimum area convex packing of P and Q, where n and m are the numbers of vertices of P and Q, respectively. |
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Yu Wang, Charlie C.L. Wang, and Matthew M.F. Yuen,
"Fast energy-based surface wrinkle modeling",
Computers & Graphics, vol.30, no.1, pp.111-125, 2006.
[PDF]
Abstract This paper presents an energy-based approach that models the distinct wrinkle shapes to represent the different material properties of non-rigid objects at an interactive speed. Our approach is a curve driven technique, where the surface wrinkles are generated by deforming the given mesh surface according to the shape change of a governing curve on the surface. An energy function is defined on the governing curve to indicate flexure properties. By minimizing the energy function, our approach offers the ability to mimic desirable and pleasing wrinkle shapes corresponding to the given material properties. We then propagate the wrinkle shape of the governing curve on the given mesh surface in the influence region. The final surface wrinkles interpolate the governing curve and are attenuated while they gradually move close to the boundary of the influence region to achieve the smoothness. Consequently, this results in the fast manipulation for complex wrinkle shapes with material properties. The most common problem of physically based simulation, the speed bottleneck, is avoided in our approach. In one word, our approach provides an efficient and useful interactive tool to model realistic wrinkles on non-rigid objects. |
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Charlie C.L. Wang, and Kai Tang,
"Optimal boundary triangulations of an interpolating ruled surface",
ASME Journal of Computing and Information Science in Engineering, vol.5, no.4, pp.291-301, 2005.
[PDF]
Abstract We investigate how to define a triangulated ruled surface interpolating two polygonal directrices that will meet a variety of optimization objectives which originate from many CAD/CAM and geometric modeling applications. This optimal triangulation problem is formulated as a combinatorial search problem whose search space however has the size tightly factorial to the numbers of points on the two directrices. To tackle this bound, we introduce a novel computational tool called multi-layer directed graph and establish an equivalence between the optimal triangulation and the single-source shortest path problem on the graph. Well known graph search algorithms such as the Dijkstra's are then employed to solve the single-source shortest path problem, which effectively solves the optimal triangulation problem in O(mn) time, where m and n are the numbers of vertices on the two directrices respectively. Numerous experimental examples are provided to demonstrate the usefulness of the proposed optimal triangulation problem in a variety of engineering applications. |
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Xiaogang Jin, Shengjun Liu, Charlie C.L. Wang, Jieqing Feng, and Hanqiu Sun,
"Blob-based liquid morphing",
Computer Animation and Virtual Worlds, Special Issue of International Conference on Computer Animation and Social Agents 2005, vol.16, no.3-4, pp.391-403, 2005.
[Animation]
[PDF]
Abstract In this paper, we propose a novel practical method for blob-based liquid 3D morphing. Firstly, blobby objects are employed to approximate a given polygonal surface through an energy optimization procedure so that the distance between the isosurface of blobs and the given model is minimized. The primitives in the medial axis sphere-tree of a polygonal model are utilized as initial blobs - this greatly improves the robustness and effciency of the blob-based approximation. Secondly, we establish the blob correspondences between two models by sphere cellular matching and hierarchial matching. Finally, we interpolate the parameters of the implicit representation to get the intermediate shapes. Experiments show our method can produce visually pleasing liquid morphing effects. |
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Charlie C.L. Wang, Kai Tang, and Benjamin M.L. Yeung,
"Freeform surface flattening by fitting a woven mesh model",
Computer-Aided Design, vol.37, no.8, pp.799-814, 2005. [Errata]
[PDF]
Abstract This paper presents a robust and efficient surface flattening approach based on fitting a woven-like mesh model on a 3D freeform surface. The fitting algorithm is based on tendon node mapping (TNM) and diagonal node mapping (DNM), where TNM determines the position of a new node on the surface along the warp or weft direction and DNM locates a node along the diagonal direction. During the 3D fitting process, strain energy of the woven model is released by a diffusion process that minimizes the deformation between the resultant 2D pattern and the given surface. Nodes mapping and movement in the proposed approach are based on the discrete geodesic curve generation algorithm, so no parametric surface or pre-parameterization is required. After fitting the woven model onto the given surface, a continuous planar coordinate mapping is established between the 3D surface and its counterpart in the plane, based on the idea of geodesic interpolation of the mappings of the nodes in the woven model. The proposed approach accommodates surfaces with darts, which are commonly utilized in clothing industry to reduce the stretch of surface forming and flattening. Both isotropic and anisotropic materials are supported. |
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Kai Tang, and Charlie C.L. Wang,
"Modeling developable folds on a strip",
ASME Journal of Computing and Information Science in Engineering, vol.5, no.1, pp.35-47, 2005. [Errata] [PDF]
Abstract A common operation in clothing and shoe design is to design a folding pattern over a narrow strip and then superimpose it with a smooth surface; the shape of the folding pattern is controlled by the boundary curve of the strip. Previous research results studying folds focused mostly on cloth modeling or in animations, which are driven more by visual realism, but allow large elastic deformations and usually completely ignore or avoid the surface developability issue. In reality, most materials used in garment and shoe industry are inextensible and uncompressible and hence any feasible folded surface must be developable, since it eventually needs to be flattened to its 2D pattern for manufacturing. Borrowing the classical boundary triangulation concept from descriptive geometry, this paper describes a computer-based method that automatically generates a specialized boundary triangulation approximation of a developable surface that interpolates a given strip. The development is achieved by geometrically simulating the folding process of the sheet as it would occur when rolled from one end of the strip to the other. Ample test examples are presented to validate the feasibility of the proposed method. |
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Charlie C.L. Wang, and Kai Tang,
"Non-self-overlapping Hermite interpolation mapping: a practical solution for structured quadrilateral meshing",
Computer-Aided Design, vol.37, no.2, pp.271-283, 2005.
[PDF]
Abstract This paper addresses the problem of constructing a structured quadrilateral grid inside a given four-sided 2D region by a particular boundary-conforming mapping scheme - Hermite Interpolation Mapping (HIM). When the four given boundary curves are concave and convoluted, all boundary-conform mapping methods suffer from potential self-overlapping problem. Under HIM, the geometry of the grid depends on both the four boundary curves and the tangent vector functions associated with the curves. While the four boundary curves are fixed, the tangent functions in HIM can be varied to suit the need of controlling the characteristics of the mesh inside the given region so to prevent self-overlapping. Besides tangent functions, the four twist vectors at the corners of the region can also be adjusted to influence the distribution of the inner grid elements. In our approach, a constrained functional optimization scheme is adopted to adjust the tangent functions and the twist vectors, adaptive to the geometry of the boundary curves, so that the resulting HIM will be free of self-overlapping. The optimization is carried out on the shape control energy that measures the overall mesh quality of the underlying HIM while the self-overlapping is strongly prevented in the form of constraints to the optimization. Experimental results show the promise of the proposed method as a practical and effective solution for structured grid generation. |
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Charlie C.L. Wang, Yu Wang, and Matthew M.F. Yuen,
"Design automation for customized apparel products",
Computer-Aided Design, vol.37, no.7, pp.675-691, 2005.
[PDF]
Abstract This paper presents solution techniques for a three-dimensional Automatic Made-to-Measure (AMM) scheme for apparel products. Freeform surface is adopted to represent the complex geometry models of apparel products. When designing the complex surface of an apparel product, abstractions are stored in conjunction with the models using a non-manifold data structure. Apparel products are essentially designed with reference to human body features, and thus share a common set of features as the human model. Therefore, the parametric feature-based modeling enables the automatic generation of fitted garments on differing body shapes. In our approach, different apparel products are each represented by a specific feature template preserving its individual characteristics and styling. When the specific feature template is encoded as the equivalent human body feature template, it automates the generation of made-to-measure apparel products. The encoding process is performed in 3D, which fundamentally solves the fitting problems of the 2D tailoring and pattern-making process. This paper gives an integrated solution scheme all above problems. In detail, a non-manifold data structure, a constructive design method, four freeform modification tools, and a detail template encoding/decoding method are developed for the design automation of customized apparel products. |
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Charlie C.L. Wang,
"Parameterization and parametric design of mannequins",
Computer-Aided Design, vol.37, no.1, pp.83-98, 2005.
[PDF]
Abstract This paper presents a novel feature based parameterization approach of human bodies from the unorganized cloud points and the parametric design method for generating new models based on the parameterization. The parameterization consists of two phases. Firstly, the semantic feature extraction technique is applied to construct the feature wireframe of a human body from laser scanned 3D unorganized points. Secondly, the symmetric detail mesh surface of the human body is modeled. Gregory patches are utilized to generate G1 continuous mesh surface interpolating the curves on feature wireframe. After that, a voxel-based algorithm adds details on the smooth G1 continuous surface by the cloud points. Finally, the mesh surface is adjusted to become symmetric. Compared to other template fitting based approaches, the parameterization approach introduced in this paper is more efficient. The parametric design approach synthesizes parameterized sample models to a new human body according to user input sizing dimensions. It is based on a numerical optimization process. The strategy of choosing samples for synthesis is also introduced. Human bodies according to a wide range of dimensions can be generated by our approach. Different from the mathematical interpolation function based human body synthesis methods, the models generated in our method have the approximation errors minimized. All mannequins constructed by our approach have consistent feature patches, which benefits the design automation of customized clothes around human bodies a lot. |
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Charlie C.L. Wang, and Kai Tang,
"Non-self-overlapping structured grid generation on an n-sided surface",
International Journal for Numerical Methods in Fluids, vol.46, no.9, pp.961-982, 2004.
[PDF]
Abstract Most existing meshing algorithms for a 2D or shell figure requires the figure to have exactly 4 sides. Generating structured grids in the n-sided parametric region of a trimmed surface thus usually requires to first partition the region into 4-sided sub-regions. We address the automatic structured grid generation problem in an n-sided region by fitting a planar Gregory patch so that the partition requirement is naturally avoided. However, self-overlapping may occur in some portions of the algebraically generated grid; this severely limits its usage in most of engineering and scientific applications where a grid system with no self-intersecting is strictly required. To solve the problem, we use a functional optimization approach to move grid nodes in the u - v domain of the trimmed surface to eliminate the self-overlapping. The derivatives of a Gregory patch, which are extremely difficult to compute analytically, are not required in our method. Thus, our optimization algorithm compares favorably at least in terms of speed with some other mesh optimization algorithms, such as elliptic PDE method. In addition, to overcome the difficulty of guessing a good initial position of every grid node for the conjugate gradient method, a progressive optimization algorithm is incorporated in our optimization. Experiment results are given to illustrate the usefulness and effectiveness of the presented method. |
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Charlie C.L. Wang, and Kai Tang,
"Achieving developability of a polygonal surface by minimum deformation: a study of global and local optimization approaches", The Visual Computer, vol.20, no.8-9, pp.521-539, 2004. [Errata]
[PDF]
Abstract Surface developability is required in a variety of applications in product design, such as clothing, ship hulls, automobile parts, etc. However, most current geometric modeling systems using polygonal surfaces ignore this important intrinsic geometric property. This paper investigates the problem of how to minimally deform a polygonal surface to attain developability, or the so called developability-by-deformation problem. In our study, this problem is first formulated as a global constrained optimization problem, and a penalty function based numerical solution is proposed for solving this global optimization problem. Next, as an alternative to the global optimization approach which usually requires lengthy computing time, we present an iterative solution based on a local optimization criterion which achieves near real-time computing speed. Both approaches preserve the topology and continuity of the original polygonal surface in the case when more than one individual polygonal patches comprise the surface. |
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Charlie C.L. Wang,
"CyberTape: an interactive measurement tool on polyhedral surface",
Computers & Graphics, vol.28, no.5, pp.731-745, 2004. [Errata]
[PDF]
Abstract Polyhedral mesh surfaces are widely utilized to represent objects reconstructed from 3D ranged images. In computer-aided engineering, it is desired to not only observe but also measure these three-dimensional objects. This paper presents an approach to measure the curve distance between two points on a polyhedral surface in the manner that simulates dragging a tapeline at the two points. After generating the initial measurement curve through the leading points in linear computing time, an iteration algorithm is presented to approximate stretching the measurement curve on the given polyhedral surface; as an option, the obtained measurement curve can be further stretched to leave the measured surface in some concave places - this likes what a tapeline behaves in reality. This novel interactive tool allows users to perform measurement tasks in an intuitive and natural way in virtual space. Our implementation algorithm can be completed in real time on a standard PC. At the end of the paper, applications of this tool are given to demonstrate its functionality. |
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Charlie C.L. Wang, and Kai Tang,
"Algebraic grid generation on trimmed surface using non-self-overlapping Coons patch mapping",
International Journal for Numerical Methods in Engineering, vol.60, no.7, pp.1259-1286, 2004.
[PDF]
Abstract Using a Coons patch mapping to generate the structured grid in the parametric region of a trimmed surface can avoid the singularity of elliptic PDE methods when only C1 continuous boundary is given; the error of converting generic parametric C1 boundary curves into a specified representation form is also avoided. However, overlap may happen on some portions of the algebraically generated grid when a linear or naive cubic blending function is used in the mapping; this severely limits its usage in most of engineering and scientific applications where a grid system of non-self-overlapping is strictly required. To solve the problem, non-trivial blending functions in a Coons patch mapping should be determined adaptively by the given boundary so that self-overlapping can be averted. We address the adaptive determination problem by a functional optimization method. The governing equation of the optimization is derived by adding a virtual dimension in the parametric space of the given trimmed surface. Both one-parameter and two-parameter blending functions are studied. To resolve the difficulty of guessing good initial blending functions for the conjugate gradient method used, a progressive optimization algorithm is then proposed which has been shown to be very effective in a variety of practical examples. Also, an extension is on the objective function to control the element shape. Finally, experiment results are shown to illustrate the usefulness and effectiveness of the presented method. |
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Charlie C.L. Wang, and Kai Tang,
"Developability-preserved free-form deformation of assembled patches",
Proceedings of ACM Symposium on Solid Modeling and Applications 2004, Genova, Italy, June 7-9, pp.231-236, 2004.
[PDF]
Abstract A novel and practical approach is presented in this paper that solves a constrained free-form deformation (FFD) problem where the developability of the tessellated embedded surface patches is preserved during the lattice deformation. The formulated constrained FFD problem has direct application in areas of product design where the surface developability is required, such as clothing, ship hulls, automobile parts, etc. In the proposed approach, the developability-preserved FFD problem is formulated as a constrained optimization problem. Different from other contained FFD approaches, the positions of lattice control points are not modified in our algorithm - as their control is insufficient in regards to the developability of all the nodes in the mesh. Moreover, the optimization is performed on the parameters of the mesh nodes rather than directly modifying their 3D coordinates, which avoids the time-consuming inverse calculation of the parameters of every node in a non-parallelepiped control lattice when further deformations are required. |
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Charlie C.L. Wang, Yu Wang, and Matthew M.F. Yuen,
"On increasing the developability of a trimmed NURBS surface",
Engineering with Computers, vol.20, no.1, pp.54-64, 2004.
[PDF]
Abstract Developable surfaces are desired in designing products manufactured from planar sheets. Trimmed NURBS surface patches are widely adopted to represent 3D products in CAD/CAM. This paper presents a new method to increase the developability of an arbitrarily trimmed NURBS surface patch. With this tool, designers can first create and modify the shape of a product without thinking about the developable constraint. When the design is finished, our approach is applied to increase the developability of the designed surface patches. Our method is an optimization based approach. After defining a function to identify the developability of a surface patch, the objective function for increasing the developability is derived. During the optimization, the positions and weights of the free control points are adjusted. When increasing the developability of a given surface patch, its deformation is also minimized and the singular points are avoided. G0 continuity is reserved on the boundary curves during the optimization, and the method to reserve G1 continuity across the boundaries is also discussed in this paper. Compared to other exist methods, our approach solves the problem in a novel way that is close to the design convention, and we are dealing with the developability problem of an arbitrarily trimmed NURBS patch |
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Charlie C.L. Wang, Yu Wang, Kai Tang, and Matthew M.F. Yuen,
"Reduce the stretch in surface flattening by finding cutting paths to the surface boundary",
Computer-Aided Design, vol.36, no.8, pp.665-677, 2004.
[PDF]
Abstract This paper presents a method for finding cutting paths on a 3D triangular mesh surface to reduce the stretch in the flattened surface. The cutting paths link the surface boundary and the nodes where the Gaussian curvature is high, and their total length is minimized. First, a linear algorithm for computing an approximate boundary geodesic distance map is introduced; the map encapsulates the undirected geodesic distance from every triangular node to the surface boundary approximately. This is followed by determining the undirected shortest paths passing through all the nodes where the Gaussian curvature is larger than a threshold. The cutting paths walk along the triangular edges of the given surface. Compared with other similar approaches, our method reaches a faster speed, and can deal with surfaces with widely distributed curvatures. |
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Charlie C.L. Wang, Yu Wang, and Matthew M.F. Yuen,
"Feature-based 3D non-manifold freeform object construction",
Engineering with Computers, vol.19, no.2-3, pp.174-190, 2003.
[PDF]
Abstract This paper presents a novel technique for modeling a 3D non-manifold freeform model around a 3D reference model. In order to represent both the design abstractions and the incomplete topological information, first of all, a new non-manifold data structure is defined. Our data structure embodies the functional vitalities of both the boundary representation data structure and the complex-based data structure. Along with our data structure, a set of topological operators is defined to manipulate the entities in the data structure. Based on the non-manifold data structure and the topological operators, we developed a technique to construct 3D freeform objects around a reference model. Intuitive 2D sketches are adopted to specify the detail profile of the constructed object. The construction method is feature based - every reference model has pre-defined features, and the feature template of the constructed object is related to the features of the reference model by feature node encoding. Therefore, the surfaces derived from one reference model can be regenerated automatically on another reference model with the same features. The geometry coverage of our geometric modeling approach includes both manifold and non-manifold 3D freeform objects. |
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Charlie C.L. Wang, Yu Wang, and Matthew M.F. Yuen,
"Feature based 3D garment design through 2D sketches",
Computer-Aided Design, vol.35, no.7, pp.659-672, 2003.
[PDF]
Abstract This paper presents a new approach for intuitively modeling a 3D garment around a 3D human model by 2D sketches input. Our approach is feature based - every human model has pre-defined features, and the constructed garments are related to the features on human models. Firstly, a feature template for creating a customized 3D garment is defined according to the features on a human model; secondly, the profiles of the 3D garment are specified through 2D sketches; finally, a smooth mesh surface interpolating the specified profiles is constructed by a modified variational subdivision scheme. The result mesh surface can be cut and flattened into 2D patterns to be manufactured. Our approach provides a 3D design tool to create garment patterns directly in the 3D space through 2D strokes, which is a characteristic not available in other computer aided garment design systems. The constructed garment patterns are related to the features on a human model, so the patterns can be regenerated automatically when creating the same style of garment for other human models. Our technique can greatly improve the efficiency and the quality of pattern making in the garment industry. |
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Charlie C.L. Wang, Yu Wang, Terry K.K. Chang, and Matthew M.F. Yuen,
"Virtual human modeling from photographs for garment industry",
Computer-Aided Design, vol.35, no.6, pp.577-589, 2003.
[PDF]
Abstract The research presented in this paper is to develop a technique of virtual human modeling for the garment industry from two photographs of a human body in two orthogonal views. Firstly, an efficient segmentation method is applied on the two photographs to obtain the contours of the human body. After that, a template-based feature extraction algorithm is introduced to determine the feature points on the human contours by human morphology rules. Finally, a view-dependent deformation technique is described to construct the virtual human body by using human contours. Our segmentation algorithm is derived from the Mumford-Shah segmentation technology and the level set formulation, and it is accelerated by applying multi-pyramid levels. The deformation technique is related to axial deformation. With our deformation method, the reference silhouettes (the front-view and right-view silhouettes of the template human model) and the target silhouettes (the front-view and right-view silhouettes of the human body from the photographs) are used to deform the template human model, which is represented by a polygonal mesh with predefined features. The self-intersection problem in the axial deformation is solved in our deformation approach. Compared with other virtual human modeling approaches, the speed of constructing the human model is increased; and our deformation technique has better continuity and local deformation properties. At the end of the paper, some potential applications for the garment industry are given to demonstrate the functionality of virtual human models constructed by our approach. |
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Charlie C.L. Wang, Terry K.K. Chang, and Matthew M.F. Yuen,
"From laser-scanned data to feature human model: a system based on fuzzy logic concept",
Computer-Aided Design, vol.35, no.3, pp.241-253, 2003.
[PDF]
Abstract This paper describes the development of a prototype system using fuzzy logic concept for constructing a feature human model, which is to be stored in a 3D digital human model database. In our approach, the feature human model is constructed by unorganized cloud points obtained from 3D laser scanners. Firstly, noisy points are removed, and the orientation of the human model is adjusted; secondly, a feature based mesh generation algorithm is applied on the cloud points to construct the mesh surface of the human model; lastly, semantic features of the human model are extracted from the mesh surface. Compared with earlier approach, our method strongly preserves the topology of a human model; more details can be constructed; and both the robustness and the efficiency of the algorithm are improved. At the end of the paper, in order to demonstrate the functionality of feature human models, potential applications are given. |
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Charlie C.L. Wang, and Matthew M.F. Yuen,
"Freeform extrusion by sketched input",
Computers & Graphics, vol.27, no.2, pp.255-263, 2003.
[PDF]
Abstract This paper presents a sketch based mesh extrusion method, which is useful for intuitive, efficient geometric modeling of freeform polygonal objects. With our method, the user can extrude either a closed or open surface from the surface or the boundary of a given mesh by sketched input. Thus, compared to earlier methods, our method provides more flexibility for solving surface modeling problems. Our mesh extrusion algorithm consists of four steps: 1) create a base curve; 2) project extruding strokes; 3) sweep a base curve; and 4) sew adjacent curves. At the end of this paper, examples of our mesh extrusion implementation are shown to demonstrate its functionality. Our freeform extrusion has been implemented as a part of our sketch based modeling system, and the mesh extrusion can be completed in real-time on a standard PC. |
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Charlie C.L. Wang, Shana S.F. Smith, and Matthew M.F. Yuen,
"Surface flattening based on energy model",
Computer-Aided Design, vol.34, no.11, pp.823-833, 2002.
[PDF]
Abstract This paper presents a method for three-dimensional surface flattening, which can be efficiently used in three-dimensional computer aided garment design. First, facet model is used to present a complex surface. Then, a spring-mass model based on energy function is used to flatten the 3D mesh surfaces into 2D patterns. The surface elastic deformation energy distribution is depicted by a color graph, which determines a surface cutting line. The method presented here can efficiently solve flattening problems for complex surfaces. The accuracy of a developed surface can easily be controlled locally. Thus, compared to earlier methods, this method provides more flexibility for solving CAD and CAM problems. |
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Charlie C.L. Wang, and Matthew M.F. Yuen,
"Sketch based mesh extrusion with remeshing techniques",
2001 ASME DETC/CIE, 21st Computers and Information in Engineering Conference,
Pittsburgh, Pennsylvania, September, 2001. (Best Paper Award)
[PDF]
Abstract In this paper, we proposed a useful 3D mesh extrusion method for intuitive, efficient geometric modeling of free-form polygonal models. With our method, the user can sketch two strokes to extrude a polygonal mesh surface. Two remeshing techniques: partial mesh re-triangulation and mesh optimization are described in this paper first. After that, the extrusion algorithm with the remeshing techniques is introduced in detail. The method can be widely used in the modeling of free-form polygonal objects. And at the end of this paper, several examples are given. |
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