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pacific conference on computer graphics and applications

作者： Sheng Li Xuehui Liu Enhua Wu Laboratory of Computer Science Institute of Software of Chinese Academy of Sciences Beijing China Department of Computer and Information Science University of Macau Macao China

ISBN: (纸本)0769520286

View-dependent level-of-detail (LOD) and visibility culling are two powerful tools for accelerating the rendering of very large models in a real-time visualization, especially in walkthrough of a large-scale terrain environment. In this paper, we propose a visibility-driven Continuous LOD (CLOD) framework for terrain, which takes advantage of both techniques. The visibility determination is based on the well-known occlusion horizon algorithm. By making use of the features of the terrain extracted in pre-processing stage, a new cascading occlusion culling (COC) algorithm is proposed to cull those regions classified as invisible to current viewpoint in real time. The time consumption and storage overheads that we spend on visibility preprocessing are quite small. Visibility-driven CLOD enhances culling efficiency and improves the frame rates significantly for walkthrough of a terrain environment.

关键词： Large-scale systems computer graphics Layout Acceleration Rendering (computer graphics) Aerospace simulation Feature extraction computer science Software tools Information science

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Controllable single-strip generation for triangulated surfaces

Controllable single-strip generation for triangulated surfac...

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pacific conference on computer graphics and applications

作者： M. Gopi Department of Computer Science University of California Irvine USA

In this paper, we introduce a method to represent a given triangular model using a single triangle strip. Since this problem is NP-complete, we break the limitation by splitting adjacent triangles when necessary. The common edge is split at the mid-point, and the newly formed triangles are coplanar with their parent triangles. Hence, the resulting geometry of the model is visually and topologically identical to the original triangular model. Our method can develop any edge-connected oriented 2-manifold of arbitrary topology, with or without boundary, into a single strip. Our stripification method can be controlled to start and end at triangles incident on specific vertices. Further, an acyclic set of edges of the input model can be marked as "constraint edges" and our method can generate a single strip that does not cross over these edges, but still cover the whole model.

关键词： Strips Solid modeling Topology Path planning Geometry computer graphics Algorithm design and analysis Process control Application software computer science

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Explicit control of topological transitions in morphing shapes of 3D meshes

Explicit control of topological transitions in morphing shap...

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pacific conference on computer graphics and applications

作者： S. Takahashi Y. Kokojima R. Ohbuchi Department of Graphics and Computer Science Graduate School of Arts and Sciences University of Tokyo Japan Corporate Research and Development Center Toshiba Corporation Japan Computer Science Department Faculty of Engineering Yamanashi University Japan

Existing methods of morphing 3D meshes are often limited to cases in which 3D input meshes to be morphed are topologically equivalent. The paper presents a new method for morphing 3D meshes having different surface topological types. The most significant feature of the method is that it allows explicit control of topological transitions that occur during the morph. Transitions of topological types are specified by means of a compact formalism that resulted from a rigorous examination of singularities of 4D hypersurfaces and embeddings of meshes in 3D space. Using the formalism, every plausible path of topological transitions can be classified into a small set of cases. In order to guide a topological transition during the morph, our method employs a key frame that binds two distinct surface topological types. The key frame consists of a pair of "faces", each of which is homeomorphic to one of the source (input) 3D meshes. Interpolating the source meshes and the key frame by using a tetrahedral 4D mesh and then intersecting the interpolating mesh with another 4D hypersurface creates a morphed 3D mesh. We demonstrate the power of our methodology by using several examples of topology transcending morphing.

关键词： Shape control computer science Topology Visual effects Research and development computer graphics Art Motion pictures TV Medical services

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RGVis: region growing based techniques for volume visualization

RGVis: region growing based techniques for volume visualizat...

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pacific conference on computer graphics and applications

作者： Runzhen Huang Kwan-Liu Ma Department of Computer Science University of California Davis USA Department of Computer Science University of California슠Davis USA

ISBN: (纸本)0769520286

Interactive data visualization is inherently an iterative trial-and-error process searching for an ideal set of parameters for classifying and rendering features of interest in the data. This paper presents 3-d region growing based techniques that can assist the users to locate and define features of interest in volume data more quickly and more accurately. One technique employs partial region growing to generate a 2-d transfer function that effectively reveals the full features of interest. The other technique uses the result of full region growing to systematically construct a boundary surface for the extracted features. The resulting polygonal representation of the boundary surface can facilitate comparison, measurement, and simulation. A visual assessment method is suggested by using the extracted volume and surface information. These techniques either shorten or completely eliminate the typical trial-and-error step in the process of interactive data exploration.

关键词： Data visualization Rendering (computer graphics) Transfer functions computer graphics Data mining Hardware Scattering computer science Feature extraction Medical simulation

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Image Recoloring with Valence-Arousal Emotion Model

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computer graphics FORUM 2016年第7期35卷 209-216页

作者： Kim, Hye-Rin Kang, Henry Lee, In-Kwon Yonsei Univ Dept Comp Sci Seoul 120749 South Korea Univ Missouri Dept Math & Comp Sci St Louis MO 63121 USA

We introduce an affective image recoloring method for changing the overall mood in the image in a numerically measurable way. Given a semantically segmented source image and a target emotion, our system finds reference image segments from the collection of images that have been tagged via crowdsourcing with numerically measured emotion labels. We then recolorize the source segments using colors from the selected target segments while preserving the gradient of the source image to generate a seamless and natural result. User study confirms the effectiveness of our method in accomplishing the stated goal of altering the mood of the image to match the target emotion level.

关键词： Categories and Subject Descriptors (according to ACM CCS) H.3.1 [INFORMATION STORAGE AND RETRIEVAL]: Content Analysis and Indexing— I.4.8 [IMAGE PROCESSING AND computer VISION]: Scene Analysis—Color

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Antialiased rendering of self-intersecting polygons using polygon decomposition

Antialiased rendering of self-intersecting polygons using po...

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pacific conference on computer graphics and applications

作者： K. Doan Canon Information Systems Research Australia North Ryde Australia

Although numerous pre-filtering and area sampling antialiasing techniques have been devised, few are capable of rendering complex, self-intersecting polygons. This paper presents a new antialiasing method capable of handling such polygons, according to any fill rule. The method is based on area sampling and is hence free from the visual aliasing artifacts of super sampling associated with near horizontal edges. It works by decomposing the coverage area of a polygon within each pixel into separate constituent regions, which are simple regions whose areas can be easily computed. The decomposition step does not attempt to generate non-overlapping regions, unlike that employed by existing methods, and hence operates very efficiently. This, together with other novel approximation techniques in the recombination stage allow pixel coverage areas to estimated with an efficiency approaching that of super sampling.

关键词： Sampling methods Image sampling computer graphics Australia Spatial resolution computer displays Frequency Low pass filters Rendering (computer graphics) Information systems

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Boundary determination for trivariate solids

Boundary determination for trivariate solids

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pacific conference on computer graphics and applications

作者： K.I. Joy M.A. Duchaineau Center for Image Processing and Integrated Computing (CIPIC) Computer Science Department University of California Davis USA Center for Applied Scientific Computing Lawrence Livemore National Laboratory USA

The trivariate tensor-product B-spline solid is a direct extension of the B-spline patch and has been shown to be useful in the creation and visualization of free-form geometric solids. Visualizing these solid objects requires the determination of the boundary surface of the solid, which is a combination of parametric and implicit surfaces. This paper presents a method that determines the implicit boundary surface by examination of the Jacobian determinant of the defining B-spline function. Using an approximation to this determinant, the domain space is adaptively subdivided until a mesh can be determined such that the boundary surface is close to linear in the cells of the mesh. A variation of the marching cubes algorithm is then used to draw the surface. Interval approximation techniques are used to approximate the Jacobian determinant and to approximate the Jacobian determinant gradient for use in the adaptive subdivision methods. This technique can be used to create free-form solid objects, useful in geometric modeling applications.

关键词： Spline Jacobian matrices Solid modeling Visualization Rendering (computer graphics) Surface cracks Image processing computer science Scientific computing Laboratories

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Adaptive reconstruction of freeform objects with 3D SOM neural network grids

Adaptive reconstruction of freeform objects with 3D SOM neur...

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pacific conference on computer graphics and applications

作者： J. Barhak A. Fischer CMSR Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion-Israel Institute of Technology Haifa Israel

Reverse engineering is an important process in CAD systems today. Yet several open problems lead to a bottleneck in the reverse engineering process. First, because the topology of the object to be reconstructed is unknown, point connectivity relations are undefined. Second, the fitted surface must satisfy global and local shape preservation criteria that are undefined explicitly. In reverse engineering, object reconstruction is based both on parameterization and on fitting. Nevertheless, the above problems are influenced mainly by parameterization. In order to overcome the above problems, the paper proposes a neural network, Self Organizing Map (SOM) method, for creating a 3D parametric grid. The main advantage of the proposed SOM method is that it detects both the orientation of the grid and the position of the sub-boundaries. The neural network grid converges to the sampled shape through an adaptive learning process. The SOM method is applied directly on 3D sampled data and avoids the projection anomalies common to other methods. The paper also presents boundary correction and growing grid extensions to the SOM method. In the surface fitting stage, an RSEC (Random Surface Error Correction) fitting method based on the SOM method was developed and implemented.

关键词： Neural networks Surface fitting Reverse engineering Surface reconstruction Shape Spline Laser modes Data mining Jacobian matrices Laboratories

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Hardware-accelerated reconstruction of polygonal isosurface representations on unstructured grids

Hardware-accelerated reconstruction of polygonal isosurface ...

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pacific conference on computer graphics and applications

作者： T. Klein S. Stegmaier T. Ertl Institute of Visualization and Interactive Systems University of Stuttgart Germany

Volume visualization using isosurface extraction is a well-researched topic. Research demonstrated that even for unstructured grids peak performances of millions of tetrahedra per second can be achieved by exploiting the parallel processing capabilities of modern GPUs. In this paper we present a hardware-accelerated solution that further improves the extraction performance. In contrary to existing approaches, our technique explicitly extracts the isosurface geometry in a fragment program by rendering only a single screen-sized quadrilateral. The extracted geometry is directly written to an on-board graphics memory object allowing for direct rendering without further bus transfers. Additionally, the geometry can be manipulated by shader programs or read back to the application for further processing. Examples and application scenarios are given that can benefit from our approach.

关键词： Isosurfaces Rendering (computer graphics) Geometry graphics Hardware Data visualization Data mining Application software Interactive systems Parallel processing

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Fast volume rendering using adaptive block subdivision

Fast volume rendering using adaptive block subdivision

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pacific conference on computer graphics and applications

作者： Choong Hwan Lee Kyu Ho Park Computer Engineering Research Laboratory Department of Electrical Engineering Korea Advanced Institute of Science and Technology Taejon South Korea

ISBN: (纸本)0818680288

We propose a fast volume rendering scheme that greatly reduces ray-casting overheads by adaptive block subdivision. We first apply a uniform space subdivision for constructing the adaptively subdivided volume. Then we merge coherent uniform blocks to generate adaptive-sized blocks that are efficient for leaping space. To accomplish this, an efficient block merging algorithm based on a boundary following and scan-filling strategy is proposed. Experimental results show that our fast volume rendering scheme is superior to other schemes in constructing a data structure for fast rendering; due to its simple construction approach, construction speed is more than three times faster than a hierarchical data structure, the octree. A 25% to 70% performance gain in rendering time over the octree is also exhibited. The additional advantages of our scheme are a stable acceleration for animation and an associativity with a compression-based volume rendering.

关键词： Space technology Merging Acceleration Laboratories Paper technology Data structures Timing Animation Data visualization computer graphics

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