Browsing by Author "Ho, Tan-Chi"

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A Simple Yet Effective User Controllable Mesh Simplification
(2013-05-01)
Ho, Tan-Chi
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Chuang, Jung-Hong
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資訊工程學系
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Department of Computer Science
Mesh simplification has become a key ingredient for real-time graphics applications. However, practitioners have found that automatic simplification methods usually fail to produce satisfactory result when models of very low polygon count are desired. This is due to the fact that existing methods take no semantic or functional metric into account, and moreover, each error metric proposed previously has its own strength and weakness. In this paper, we propose a user-controllable mesh simplification framework that allows users to achieve a predictable resolution improvement in selected regions of a simplified mesh derived by using any error metric. The framework consists of two stages. The first stage employs weighting schemes that allow users to refine unsatisfactory regions to a user-expected resolution. The second stage is a local refinement aiming to provide a user-guided fine-tune to recover local sharp features. Two weighting schemes, namely uniform weighting and nonuniform weighting, are proposed. In uniform weighting scheme, a weight value is applied to all original mesh vertices in a selected region, resulting in a uniform improvement on vertex resolution in the region, while in the nonuniform weighting scheme varying weights are applied to vertices in a selected region and obtain a nonuniform resolution improvement in the region. Different from the previous user-assisted simplification methods that reorder the collapsing sequence indirectly by weighting the collapsing cost of edges, the two proposed weighting schemes directly reorder the edge collapsing sequence, ensuring a predictable resolution improvement in the selected regions. Moreover, the proposed weighting schemes are independent on error metric used for simplification and ensure the same resolution improvement when a weighting value is applied to simplified meshes with different resolutions.
A Skeleton-Based Approach for Consistent Segmentation Transfer
(2014-07-01)
Wong, Sai-Keung
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Yang, Jau-An
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Ho, Tan-Chi
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Chuang, Jung-Hong
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資訊工程學系
We present a skeleton-based approach for mapping consistently a segmentation of a source mesh to a target mesh. The source and target meshes are semantically similar but their geometries may be different. We assume that the segmentation of the source mesh and the skeleton correspondence between the meshes are provided. Our method first establishes the skeleton-boundary correspondence and then performs the boundary transfer procedure. The skeleton-boundary correspondence is useful for computing approximately the target boundaries. The boundary transfer procedure aims to produce the segment boundaries of the target mesh such that their geometric details are consistent to the ones of the corresponding source segment boundaries. We have applied our method for various models and compared with the state-of-the-art techniques. Our method computes segment boundaries of the target mesh which are similar to the ones of the source mesh.
Fire synthesis using basis fires and design
(2017-03-01)
Wong, Sai-Keung
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Chang, Tse-Ching
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Ho, Tan-Chi
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Chuang, Jung-Hong
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交大名義發表
In this paper, we present an approach to use basis fires to design and synthesize fires in desired shapes and motions. In the preprocessing stage, each basis fire is simulated based on a physics-based fire simulator with a specific simulation configuration. The pathlines and temperatures of the basis fires are stored in a database. In the fire design stage, a user inputs a sequence of curves which represent the desired shapes of fires. In the fire synthesis stage, we use a least-square fitting method to fit the curves using the pathlines and temperatures of the basis fires. In the fire animation stage, we adopt a modified motion graph for animating the synthesized fires. We have applied our approach to synthesize fires with different shapes and motions. Experimental results show that our approach is easy to use and it can produce fires with desired shapes in an intuitive manner. The synthesized fire can be animated at real-time rates.
Interactive Lighting Design with Hierarchical Light Representation
(2013-06-01)
Lin, Wen-Chieh
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Huang, Tsung-Shian
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Ho, Tan-Chi
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Chen, Yueh-Tse
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Chuang, Jung-Hong
Lighting design plays a crucial role in indoor lighting design, computer cinematograph and many other applications. Computer-assisted lighting design aims to find a lighting configuration that best approximates the illumination effect specified by designers. In this paper, we present an automatic approach for lighting design, in which discrete and continuous optimization of the lighting configuration, including the number, intensity, and position of lights, are achieved. Our lighting design algorithm consists of two major steps. The first step estimates an initial lighting configuration by light sampling and clustering. The initial light clusters are then recursively merged to form a light hierarchy. The second step optimizes the lighting configuration by alternatively selecting a light cut on the light hierarchy to determine the number of representative lights and optimizing the lighting parameters using the simplex method. To speed up the optimization computation, only illumination at scene vertices that are important to rendering are sampled and taken into account in the optimization. Using the proposed approach, we develop a lighting design system that can compute appropriate lighting configurations to generate the illumination effects iteratively painted and modified by a designer interactively.
Interactive Visual Analysis of Browsing and Authoring Behaviors in Web Media
(2015)
Kuan, Yen-Ting
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Tai, Ming-Hung
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Kuan, Hsuan-Hao
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Ho, Tan-Chi
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Wang, Yu-Shuen
Web media is becoming popular nowadays for people to read news or articles. It is interesting and important for the web media providers to learn the browsing behaviors of their readers and authors. In this paper, we present a visual analytics system for discovering the browsing and authoring behaviors in web media based on users web page clickstream data. Our system provides multiple views of visualization with user interaction, including a scatter plot providing an overview to help analysts locate data of interest, and a force-directed graph for investigating relations between data entities. Interesting behaviors have been explored and found by using the proposed multiple views system.
Real-time translucent rendering using GPU-based texture space importance sampling
(2008-04-01)
Chang, Chih-Wen
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Lin, Wen-Chieh
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Ho, Tan-Chi
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Huang, Tsung-Shian
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Chuang, Jung-Hong
We present a novel approach for real-time rendering of translucent surfaces. The computation of subsurface scattering is performed by first converting the integration over the 3D model surface into an integration over a 2D texture space and then applying importance sampling based on the irradiance stored in the texture. Such a conversion leads to a feasible GPU implementation and makes real-time frame rate possible. Our implementation shows that plausible images can be rendered in real time for complex translucent models with dynamic light and material properties. For objects with more apparent local effect, our approach generally requires more samples that may downgrade the frame rate. To deal with this case, we decompose the integration into two parts, one for local effect and the other for global effect, which are evaluated by the combination of available methods [DS03, MKB* 03a] and our texture space importance sampling, respectively. Such a hybrid scheme is able to steadily render the translucent effect in real time with a fixed amount of samples.
Volume Based Mesh Segmentation
(2012-07-01)
Ho, Tan-Chi
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Chuang, Jung-Hong
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資訊工程學系
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Department of Computer Science
"Mesh segmentation has become a key ingredient in many mesh applications in computer graphics. In this paper, we propose a hierarchical segmentation that decomposes a polygonal object into meaningful parts in such a way that not only components on a higher level reveal higher degree of salience than their descendant parts but also the components on each level of hierarchy have similar degree of salience. Moreover, the number of boundaries on each level of the hierarchy is determined automatically. The proposed segmentation is based on the Minimum Slice Perimeter (MSP) function [1], which represents non-local shape features and has better interpretation for the object parts. The gradient of MSP function is used to locate the segmentation regions and a new measure of part salience is proposed to evaluate the significance of the segmentation regions. For each level of hierarchy, some most perceptually significant segmentation regions are selected based on their salience measures and boundaries are then computed from the selected segmentation regions by using a capacity that considers both the curvature and MSP gradient."