Hock Soon Seah

Nanyang Technological University, Tumasik, Singapore

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Publications (114)56.05 Total impact

  • Lu Dong · Yuming Fang · Weisi Lin · Hock Soon Seah
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    ABSTRACT: Triangle meshes are used in representation of 3D geometric models, and they are subject to various visual distortions during geometrical processing and transmission. In this study, we propose a novel objective quality assessment method for 3D meshes based on curvature information; according to characteristics of the human visual system (HVS), two new components including visual masking and saturation effect are designed for the proposed method. Besides, inspired by the fact that the HVS is sensitive to structural information, we compute the structure distortion of 3D meshes. We test the performance of the proposed method on three publicly available databases of 3D mesh quality evaluation. We rotate among these databases for parameter determination to demonstrate the robustness of the proposed scheme. Experimental results demonstrate that the proposed method can predict consistent results in terms of correlation to the subjective scores across the databases.
    No preview · Article · Dec 2015 · IEEE Transactions on Multimedia
  • Nicholas Mario Wardhana · Henry Johan · Hock Soon Seah
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    ABSTRACT: Modern computer graphics applications commonly feature very large virtual environments and diverse characters which perform different kinds of motions. To accelerate path planning in such a scenario, we propose the subregion graph data structure. It consists of subregions, which are clusters of locally connected waypoints inside a region, as well as subregion connectivities. We also present a fast algorithm to automatically generate a subregion graph from an enhanced waypoint graph map representation, which also supports various motion types and can be created from large virtual environments. Nevertheless, a subregion graph can be generated from any graphbased map representation. Our experiments show that a subregion graph is very compact relative to the input waypoint graph. By firstly planning a subregion path, and then limiting waypoint-level planning to this subregion path, over 8 times average speedup can be achieved, while average length ratios remain as low as 102.5%.
    No preview · Article · Jun 2015
  • Jigang Liu · Dongquan Liu · Justin Dauwels · Hock Soon Seah
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    ABSTRACT: 3D human motion tracking has received increasing attention in recent years due to its broad applications. Among various 3D human motion tracking methods, the particle filter is regarded as one of the most effective algorithms. However, there are still several limitations of current particle filter approaches such as low prediction accuracy and sensitivity to discontinuous motion caused by low frame rate or sudden change of human motion velocity. Targeting such problems, this paper presents a full-body human motion tracking system by proposing exemplar-based conditional particle filter (EC-PF) for monocular camera. By introducing a conditional term with respect to exemplars and image data, dynamic model is approximated and used to predict current states of particles in prediction phase. In update phase, weights of particles are refined by matching images with projected human model using a set of features.
    No preview · Article · May 2015 · Signal Processing
  • C.K. Quah · X. Xu · H.S. Seah
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    ABSTRACT: Curves and lines are fundamental elements in animation sketches. To sketch an animation sequence manually would be a very laborious task. Also to enable these curves and lines to be manipulated efficiently would be very important for productivity. Here we propose a 3D model-based approach for generating 2D and 3D curves from a 3D animation sequence. We introduce an automatic method to extract 3D and 2D feature curves from the 3D animation through curve tracing, matching and evolving. All the 3D and 2D curves extracted are spatially and temporally coherent. Moreover, the geometrical relationship between the 2D and 3D curves are established. The curves are processed and vectorized to allow artists to intuitively edit and author the animation by manipulating the 3D and 2D features. By using distinct points on the feature curves as basis, we apply the radial basis function to deform the entire geometry of the animated model across the entire sequence. The result showed that our method has promising potential to make the animation process to be more time efficient.
    No preview · Article · Mar 2015
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    ABSTRACT: Curve extension is a useful function in CAD systems. Disk B-Spline curve has its distinct advantages in representing a 2D region. This paper presents an algorithm for extending the disk B-Spline curve with G2 continuity. A disk Bezier segment is used to construct the extending part and G2-continuity can be used to describe the smoothness at the joint disk. Fairness of the extending disk Bezier curve segment is achieved by minimizing energy objective functions for the center curve and the radius function separately. New control disks are computed by unclamping algorithm to represent the whole extended disk B-Spline curve. The experimental results demonstrate the effectiveness of our method.
    No preview · Article · Mar 2015 · Computer-Aided Design and Applications
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    Yaqiong Liu · Hock Soon Seah
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    ABSTRACT: Recently, points of interest (POIs) recommendation has evolved into a hot research topic with real-world applications. In this paper, we propose a novel semantics-enhanced density-based clustering algorithm SEM-DTBJ-Cluster, to extract semantic POIs from GPS trajectories. We then take into account three different factors (popularity, temporal and geographical features) that can influence the recommendation score of a POI. We characterize the impacts caused by popularity, temporal and geographical information, by using different scoring functions based on three developed recommendation models. Finally, we combine the three scoring functions together and obtain a unified framework PTG-Recommend for recommending candidate POIs for a mobile user. To the best of our knowledge, this work is the first that considers popularity, temporal and geographical information together. Experimental results on two real-world data sets strongly demonstrate that our framework is robust and effective, and outperforms the baseline recommendation methods in terms of precision and recall.
    Full-text · Article · Mar 2015 · International Journal of Geographical Information Science
  • Lu Dong · Yuming Fang · Weisi Lin · Chenwei Deng · Ce Zhu · Hock Soon Seah
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    ABSTRACT: Since the human visual system (HVS) is the ultimate appreciator of most photorealistically rendered images, rendering process can be accelerated by exploiting the properties of the HVS. According to the concept of entropy masking, the HVS is not sensitive to visual distortions in unstructured visual signals. For structured regions, pixels are highly correlated, while the similarity among pixels in unstructured regions is low. In this paper, we detect unstructured regions by extracting local patches from each pixel and its neighboring pixels, and comparing the similarity between the local patches of the center pixel and the neighboring pixels. We further exploit entropy masking in perceptual rendering, and experimental results demonstrate that the proposed method can accelerate rendering, without degrading the perceived quality of resultant images.
    No preview · Article · Feb 2015 · Signal Processing Image Communication
  • Lu Dong · Yuming Fang · Weisi Lin · Hock Soon Seah
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    ABSTRACT: 3D triangle meshes are widely used in representation of graphic data, and they are subject to various visual distortions during geometry processing and transmission. In this study, we propose a novel objective quality assessment method for 3D meshes based on curvature information. According to characteristics of the human visual system (HVS), two new components including visual masking modulation and saturation effect modulation are designed for the proposed method. Besides, inspired by the fact that the HVS is sensitive to structural information, we compute the structure distortion for 3D meshes. We test the performance of the proposed method on three publicly available databases of 3D mesh quality evaluation, and compare the performance of the proposed method with the relevant state-of-the-art methods. Experimental results demonstrate that the proposed method can predict consistent results in terms of correlation to the subjective scores across these databases.
    No preview · Article · Dec 2014
  • Hui Liu · Feng Lin · Kemao Qian · Hock Soon Seah · Yong Tsui Lee
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    ABSTRACT: Prediction of the 3D structure of protein-protein complexes is crucial for understanding the biological system of life and thus for designing drugs. However it is a challenging problem due to the flexibility of the backbone and side-chains of the receptor and ligand. In this paper, we present a new framework for fast and flexible protein-protein docking based on geometric and physicochemical complementarity. In our approach, we segment the protein surfaces into several local surface patches and describe the effect of side-chain flexibility on each patch by sampling the space of conformation of its side-chains. Then the geometric complementarity can be determined by matching these surface patches. During the matching, we propose a new 3D shape descriptor, Spherical Harmonics Descriptor. The main property of the Spherical Harmonics Descriptor is rotation invariance which avoids taking an exhaustive set of rotations for each pair of patches. Thus, the geometric complementarity matching problem is simplified to a histogram matching problem. This can greatly reduce the computational cost. Finally, the docking candidates are evaluated by a scoring function which can accommodate geometric complementarity and physicochemical matching. The experimental results demonstrate the high efficiency and accuracy of the proposed method.
    No preview · Article · Sep 2014
  • Budianto Tandianus · Henry Johan · Hock Soon Seah · Feng Lin
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    ABSTRACT: Erratum to: Vis Comput DOI 10.1007/s00371-014-1037-zThe published paper contains a minor error (note the section highlighted with bold formatting) in the Abstract which we wish to make a correction on:\(\ldots \) Secondly, by considering the surrounding objects (their material reflectance from and visible surface area of the caustic objects) and light power, we compute the refinement amount of each wavelength cluster. Our accelerated \(\ldots \)Should be written as:\(\ldots \) Secondly, by considering the surrounding objects (their material reflectance and their visible surface area from the caustic objects) and light power, we compute the refinement amount of each wavelength cluster. Our accelerated \(\ldots \)
    No preview · Article · Mar 2014 · The Visual Computer
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    ABSTRACT: Curve blending is an essential task in geometric modeling, while a ball B-spline curve (BBSC) has its advantages in representing freeform tubular objects. This paper proposes a blending algorithm for ball B-Spline curve with G2 continuity, which is used to describe the smoothness of the joint point. An original BBSC is extended smoothly to join another one, such that no additional blending curve is created and the two original curves are not changed. The shape of the extended curve is then determined by minimizing strain energy. The corresponding scalar function of the control balls is determined through applying G2-continuity conditions to the scalar function. In order to ensure the radii of the control balls are positive, we make a decision about the range of the G2-continuity parameter and then determine it by minimizing the strain energy in the affected area. The experiment results demonstrate our method for blending BBSC is effective. Moreover, some G2 blending results of the BBSC in simulating the tubular objects are given.
    No preview · Conference Paper · Nov 2013
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    ABSTRACT: Curve extension is a useful function in CAD systems. Disk B-Spline curve has its distinct advantages in representing a 2D region. This paper presents an algorithm for extending the disk B-Spline curve. A disk Bezier segment is used to construct the extending part and G2-continuity can be used to describe the smoothness of the joint disk. Fairness of the extending disk Bezier segment is achieved by minimizing an energy objective function. New control disks are computed by unclamping algorithm to represent the whole extended disk B-Spline curve. The experimental results demonstrate the effectiveness of our method.
    No preview · Conference Paper · Nov 2013
  • Yaqiong Liu · Hock Soon Seah · Gao Cong
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    ABSTRACT: Given a set of moving clients as well as their friend relationships, a road network, and a distance threshold per friend pair, the proximity detection problem in road networks is to find each pair of friends such that the road network distance between them is within the given threshold. The problem of proximity detection is often encountered in friend-locator applications and massively multiplayer online games. Because of the limited battery power and bandwidth, it is better to develop a solution which incurs less communication cost. Hence, the main objective of this problem is to reduce the total communication cost. However, most of the existing proximity detection solutions focus on the Euclidean space but cannot be used in road network space; the solutions for road networks incur substantial communication costs. Motivated by this, we propose two types of solutions to solve the proximity detection problem in road networks. In the first type of solution, each mobile client is assigned with a mobile region of a fixed size. We design algorithms with a fixed radius for the client and server respectively, with the purpose of reducing unnecessary probing messages and update messages. Second, we present a self-tuning policy to adjust the radius of the mobile region automatically to minimize the communication cost. Experiments show that our second type of solution works efficiently and robust with a much lower communication cost with respect to various parameters. In addition, we present our server-side computational cost optimization techniques to reduce the total computational cost.
    No preview · Conference Paper · Nov 2013
  • Nicholas Mario Wardhana · Henry Johan · Hock Soon Seah
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    ABSTRACT: Our research focuses on the problem of path planning in 3D virtual world applications. The characters we consider are heterogeneous, as they have different sizes, and can perform surface or volumetric motion. In this paper, we propose an enhanced waypoint graph, which consists of point nodes equipped with radius, as well as edges connecting those nodes. Each edge is labeled with the motion type it can support. Given a polygon soup representation of a virtual world, the proposed algorithm starts by subdividing the virtual world into regions. This enables us to process large virtual worlds. Each region is then locally voxelized, one at a time. Two kinds of waypoints are generated: local waypoints using corner detection on the voxelization, and border waypoints at the region boundary. Waypoints are then sparsely connected to form a local waypoint graph, and local graphs are finally connected via the border waypoints to create the final global enhanced waypoint graph. To plan paths between arbitrary points using this graph, the points are connected to the graph using nearest neighbor search and traversability test, then Dijkstra/A* algorithm is used to calculate the final path, taking into account the appropriate size and motion type.
    No preview · Article · Oct 2013 · The Visual Computer
  • X. Xu · H. S. Seah · C. K. Quah
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    ABSTRACT: Producing traditional animation is a laborious task where the key drawings are first drawn by artists and thereafter inbetween drawings are created, whether it is by hand or computer‐assisted. Auto‐inbetweening of these 2D key drawings by computer is a non‐trivial task as 3D depths are missing. An alternate approach is to generate all the drawings by extracting lines directly from animated 3D models frame by frame, concatenating and rendering them together into an animation. However, animation quality generated using this straightforward method bears two problems. Firstly, the animation contains unsatisfactory visual artifacts such as line flickering and popping. This is especially pronounced when the lines are extracted using high‐order derivatives, such as ridges and valleys, from 3D models represented in triangle meshes. Secondly, there is a lack of temporal continuity as each drawing is generated without taking its neighboring drawings into consideration. In this paper, we propose an improved approach over the straightforward method by transferring extracted 3D line drawings of each frame into individual 3D lines and processing them along the time domain. Our objective is to minimize the visual artifacts and incorporate temporal relationship of individual lines throughout the entire animation sequence. This is achieved by creating correspondent trajectory of each line from each frame and applying global optimization on each trajectory. To realize this target, we present a fully automatic novel approach, which consists of (1) a line matching algorithm, (2) an optimizing algorithm, taking into account both the variations of numbers and lengths of 3D lines in each frame, and (3) a robust tracing method for transferring collections of line segments extracted from the 3D models into individual lines. We evaluate our approach on several animated model sequences to demonstrate its effectiveness in producing line drawing animations with temporal coherence.
    No preview · Article · Oct 2013 · Computer Graphics Forum
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    Jooyoung Hahn · Jie Qiu · Eiji Sugisaki · Lei Jia · Xue-Cheng Tai · Hock Soon Seah
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    ABSTRACT: We present a surface reconstruction via 2D strokes and a vector field on the strokes based on a two-step method. In the first step, from sparse strokes drawn by artists and a given vector field on the strokes, we propose a nonlinear vector interpolation combining total variation and H 1 regularization with a curl-free constraint for obtaining a dense vector field. In the second step, a height map is obtained by integrating the dense vector field in the first step. Jump discontinuities in surface and discontinuities of surface gradients can be well reconstructed without any surface distortion. We also provide a fast and efficient algorithm for solving the proposed functionals. Since vectors on the strokes are interpreted as a projection of surface gradients onto the plane, different types of strokes are easily devised to generate geometrically crucial structures such as ridge, valley, jump, bump, and dip on the surface. The stroke types help users to create a surface which they intuitively imagine from 2D strokes. We compare our results with conventional methods via many examples.
    Full-text · Article · Feb 2013 · Numerical Mathematics Theory Methods and Applications
  • Lu Dong · Weisi Lin · Chenwei Deng · Ce Zhu · Hock Soon Seah
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    ABSTRACT: For high-quality image rendering using Monte Carlo methods, a large number of samples are required to be computed for each pixel. Adaptive sampling aims to decrease the total number of samples by concentrating samples on difficult regions. However, existing adaptive sampling schemes haven't fully exploited the potential of image regions with complex structures to the reduction of sample numbers. To solve this problem, we propose to exploit uncertainty masking in adaptive sampling. Experimental results show that incorporation of uncertainty information leads to significant sample reduction and therefore time-savings.
    No preview · Conference Paper · Jan 2013
  • Lu Dong · Weisi Lin · Yuming Fang · Shiqian Wu · Hock Soon Seah
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    ABSTRACT: In this work, we propose a novel graphic saliency detection method to detect visually salient objects in images rendered from 3D geometry models. Different from existing graphic saliency detection methods, which estimate saliency based on pixel-level contrast, the proposed method detects salient objects by computing object-level contrast. Given a rendered image, the proposed method first extracts dominant colors from each object, and represents each object with a dominant color descriptor (DCD). Saliency of each object is then calculated by measuring the contrast between the DCD of the object and the DCDs of its surrounding objects. We also design a new iterative suppression operator to enhance the saliency result. Compared with existing graphic saliency detection methods, the proposed method can obtain much better performance in salient object detection. We further apply the proposed method to selective image rendering and achieve better performance over the relevant existing algorithm.
    No preview · Article · Jan 2013 · Journal of Visual Communication and Image Representation
  • Wei Ming Chiew · Feng Lin · Kemao Qian · Hock Soon Seah
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    ABSTRACT: Modern microscopic volumetric imaging processes lack capturing flexibility and are inconvenient to operate. Additionally, the quality of acquired data could not be assessed immediately during imaging due to the lack of a coherent real-time visualization system. Thus, to eliminate the requisition of close user supervision while providing real-time 3D visualization alongside imaging, we propose and describe an innovative approach to integrate imaging and visualization into a single pipeline called an online incrementally accumulated rendering system. This system is composed of an electronic controller for progressive acquisition, a memory allocator for memory isolation, an efficient memory organization scheme, a compositing scheme to render accumulated datasets, and accumulative frame buffers for displaying non-conflicting outputs. We implement this design using a laser scanning confocal endomicroscope, interfaced with an FPGA prototyping board through a custom hardware circuit. Empirical results from practical implementations deployed in a cancer research center are presented in this paper.
    No preview · Article · Jan 2013 · Computers in Industry
  • Lu Dong · Weisi Lin · Yuming Fang · Shiqian Wu · Hock Soon Seah
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    ABSTRACT: In this work, we propose a method to detect visually salient objects in computer synthesized images from 3D meshes. Different from existing detection methods on graphic saliency which compute saliency based on pixel-level contrast, the proposed method computes saliency by measuring object-level contrast of each object to the other objects in a rendered image. Given a synthesized image, the proposed method first extracts dominant colors from each object, and represents each object with the dominant color descriptor (DCD). Saliency is measured as the contrast between the DCD of the object and the DCDs of its surrounding objects. We evaluate the proposed method on a data set of computer rendered images, and the results show that the proposed method obtains much better performance compared with existing related methods.
    No preview · Conference Paper · Jan 2013