Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883882
WongPing Wah
In particle-tracing radiosity algorithms, energy-carrying particles are traced through an environment for simulating global illumination. Illumination on a surface is reconstructed from particle "hit points" on the surface, which is a density estimation problem (B.W. Silverman, 1986). Several methods can be used to solve this problem, such as the adaptive meshing method (R.F. Tobler et al., 1997), the kernel method (B. Walter et al., 1997), and the orthogonal series estimator (M. Feda, 1996). An orthogonal series estimator is proposed to tackle the problem. In the new method, the appropriate number of terms that should be used in the series is determined adaptively and automatically. Moreover a surface subdivision scheme is combined with the estimator to increase the accuracy of estimation. The new method has several advantages over other existing methods: (1) it requires less memory than the adaptive meshing method; (2) it does not store all the particle-hit points as in the kernel method; (3) it determines automatically how many terms should be used in the orthogonal series; (4) it incorporates surface subdivision to further increase the accuracy of estimation.
{"title":"A new adaptive density estimator for particle-tracing radiosity","authors":"WongPing Wah","doi":"10.1109/PCCGA.2000.883882","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883882","url":null,"abstract":"In particle-tracing radiosity algorithms, energy-carrying particles are traced through an environment for simulating global illumination. Illumination on a surface is reconstructed from particle \"hit points\" on the surface, which is a density estimation problem (B.W. Silverman, 1986). Several methods can be used to solve this problem, such as the adaptive meshing method (R.F. Tobler et al., 1997), the kernel method (B. Walter et al., 1997), and the orthogonal series estimator (M. Feda, 1996). An orthogonal series estimator is proposed to tackle the problem. In the new method, the appropriate number of terms that should be used in the series is determined adaptively and automatically. Moreover a surface subdivision scheme is combined with the estimator to increase the accuracy of estimation. The new method has several advantages over other existing methods: (1) it requires less memory than the adaptive meshing method; (2) it does not store all the particle-hit points as in the kernel method; (3) it determines automatically how many terms should be used in the orthogonal series; (4) it incorporates surface subdivision to further increase the accuracy of estimation.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"79 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123344966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883852
G. Baranoski, P. Shirley, J. Rokne, T. Trondsen, R. Bastos
We present an algorithm to simulate the aurora borealis, commonly known as the "northern lights", a natural phenomenon of great visual beauty and considerable scientific interest. The algorithm is based on the current understanding of the physical origin of the aurora. This natural display is mainly caused by high-energy electrons originating in the Sun and entering the Earth's atmosphere in narrow regions centered on the magnetic poles. These electrons collide with atmospheric atoms which are excited to higher energy levels. The excited atoms emit rapidly varying visible light in a curtain-like volume as they return to lower energy levels thereby creating the aurora. By simulating these light emissions along with the spatial and temporal distribution of the entering electrons, we are able to render the major visual aspects of auroral displays. This approach also allows the representation of time-dependent features that characterize the dynamic nature of the aurorae. The applicability of this auroral model for artistic and research purposes is illustrated through comparisons of synthetic images with photographs of real auroral displays.
{"title":"Simulating the aurora borealis","authors":"G. Baranoski, P. Shirley, J. Rokne, T. Trondsen, R. Bastos","doi":"10.1109/PCCGA.2000.883852","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883852","url":null,"abstract":"We present an algorithm to simulate the aurora borealis, commonly known as the \"northern lights\", a natural phenomenon of great visual beauty and considerable scientific interest. The algorithm is based on the current understanding of the physical origin of the aurora. This natural display is mainly caused by high-energy electrons originating in the Sun and entering the Earth's atmosphere in narrow regions centered on the magnetic poles. These electrons collide with atmospheric atoms which are excited to higher energy levels. The excited atoms emit rapidly varying visible light in a curtain-like volume as they return to lower energy levels thereby creating the aurora. By simulating these light emissions along with the spatial and temporal distribution of the entering electrons, we are able to render the major visual aspects of auroral displays. This approach also allows the representation of time-dependent features that characterize the dynamic nature of the aurorae. The applicability of this auroral model for artistic and research purposes is illustrated through comparisons of synthetic images with photographs of real auroral displays.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133996997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883965
P. Lecocq, A. Kemeny, Sylvain Michelin, D. Arquès
Many shading models are able to provide realistic rendering of lighting effects under various atmospheric conditions but computational times are often expensive. This paper proposes a method to render lighting effects within participating media in real-time on a graphics workstation. It consists of mathematical approximations based on a re-formulation of the light transport equation considering atmospheric scattering with light sources described by their luminous intensity distribution. Hardware capabilities of graphics computer boards are used to accelerate parts of the rendering process.
{"title":"Mathematical approximation for real-time lighting rendering through participating media","authors":"P. Lecocq, A. Kemeny, Sylvain Michelin, D. Arquès","doi":"10.1109/PCCGA.2000.883965","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883965","url":null,"abstract":"Many shading models are able to provide realistic rendering of lighting effects under various atmospheric conditions but computational times are often expensive. This paper proposes a method to render lighting effects within participating media in real-time on a graphics workstation. It consists of mathematical approximations based on a re-formulation of the light transport equation considering atmospheric scattering with light sources described by their luminous intensity distribution. Hardware capabilities of graphics computer boards are used to accelerate parts of the rendering process.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134360541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883886
Tatiana Surazhsky, G. Elber
A novel method for the layout of text strings over some given free-form parametric base curves is considered. Each letter of the string is represented by a collection of cubic and linear Bezier curves. The layout of the string over the free-form parametric curve is derived as a symbolic composition of the string geometry (i.e. a sequence of Bezier curves) and a free-form parametric surface S(u, v) with the parameters u, v between zero and one, and S(u, 0) given by the base curve. This method has proven to provide great flexibility and give high quality results in layout of text.
{"title":"Arbitrary precise orientation specification for layout of text","authors":"Tatiana Surazhsky, G. Elber","doi":"10.1109/PCCGA.2000.883886","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883886","url":null,"abstract":"A novel method for the layout of text strings over some given free-form parametric base curves is considered. Each letter of the string is represented by a collection of cubic and linear Bezier curves. The layout of the string over the free-form parametric curve is derived as a symbolic composition of the string geometry (i.e. a sequence of Bezier curves) and a free-form parametric surface S(u, v) with the parameters u, v between zero and one, and S(u, 0) given by the base curve. This method has proven to provide great flexibility and give high quality results in layout of text.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"249 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133549924","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883949
Yong Lu, R. Gadh
Volume decomposition is a fundamental issue that draws attention from researchers in different disciplines. In many contexts, a solid model that contains shape information needs to be partitioned into smaller simpler or more meaningful sub-models in order to facilitate efficient or effective analysis. Much progress has been made so far on convex decomposition of polyhedra and relatively difficult geometries; general decomposition on a CAD model with arbitrary shapes to produce intelligent partitions is still highly challenging. The constrained and aggregated half-space volume decomposition approach is aimed at improving the efficiency and intelligence of decomposition by trimming and aggregating cutting surfaces. In this paper, two kinds of extending strategies ("internal" extending and "external" extending) are identified and the algorithms for them are demonstrated.
{"title":"Constrained and aggregated half space volume decomposition: generating cutting patches with \"internal\" and \"external\" extending","authors":"Yong Lu, R. Gadh","doi":"10.1109/PCCGA.2000.883949","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883949","url":null,"abstract":"Volume decomposition is a fundamental issue that draws attention from researchers in different disciplines. In many contexts, a solid model that contains shape information needs to be partitioned into smaller simpler or more meaningful sub-models in order to facilitate efficient or effective analysis. Much progress has been made so far on convex decomposition of polyhedra and relatively difficult geometries; general decomposition on a CAD model with arbitrary shapes to produce intelligent partitions is still highly challenging. The constrained and aggregated half-space volume decomposition approach is aimed at improving the efficiency and intelligence of decomposition by trimming and aggregating cutting surfaces. In this paper, two kinds of extending strategies (\"internal\" extending and \"external\" extending) are identified and the algorithms for them are demonstrated.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"53 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130362289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883962
Terii Stein, S. Coquillart
This paper proposes a new interaction technique for positioning or moving 3D points, which is a basic task in geometric modeling and several other applications. These systems usually make use of a 2D interface with a 2D cursor. However positioning 3D points with a 2D cursor is often done by using several windows, each window displaying a different orthographic projection of the 3D space. This paper introduces the Metric Cursor, a multi-purpose 3D cursor which moves freely in the 3D space, requires only one window and provides the user with different helpful functionalities such as grids and some measurement capabilities.
{"title":"The metric cursor","authors":"Terii Stein, S. Coquillart","doi":"10.1109/PCCGA.2000.883962","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883962","url":null,"abstract":"This paper proposes a new interaction technique for positioning or moving 3D points, which is a basic task in geometric modeling and several other applications. These systems usually make use of a 2D interface with a 2D cursor. However positioning 3D points with a 2D cursor is often done by using several windows, each window displaying a different orthographic projection of the 3D space. This paper introduces the Metric Cursor, a multi-purpose 3D cursor which moves freely in the 3D space, requires only one window and provides the user with different helpful functionalities such as grids and some measurement capabilities.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115551715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883898
Yuya Iwakiri, Yuuichi Omori, T. Kaneko
Concerns the problem of mapping photographic images on to the surface of a 3D object whose geometric data are already known. Although the minimal view selection algorithm of K. Matsushita and T. Kaneko (1999) enables the selection of a minimal number of camera positions, it often results in untextured patches due to camera misalignment: a deviation of actual camera position from the specified position. This paper proposes two new practical algorithms (double and product viewing) to ensure that all the polygons are textured even if there are unavoidable human errors in camera alignment. The performance of the algorithms is evaluated by simulation experiments.
{"title":"Practical texture mapping on free-form surfaces","authors":"Yuya Iwakiri, Yuuichi Omori, T. Kaneko","doi":"10.1109/PCCGA.2000.883898","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883898","url":null,"abstract":"Concerns the problem of mapping photographic images on to the surface of a 3D object whose geometric data are already known. Although the minimal view selection algorithm of K. Matsushita and T. Kaneko (1999) enables the selection of a minimal number of camera positions, it often results in untextured patches due to camera misalignment: a deviation of actual camera position from the specified position. This paper proposes two new practical algorithms (double and product viewing) to ensure that all the polygons are textured even if there are unavoidable human errors in camera alignment. The performance of the algorithms is evaluated by simulation experiments.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123642554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883938
Manuel Carcenac, A. Acan
Presents a novel method for modeling an isosurface that is defined by an unstructured set of control points. The principle is to model the scalar field underlying the isosurface with a neural network: the inputs of the neural network are the three coordinates of a point in space, and its output is the value of the scalar field at this point. The isosurface is requested to satisfy some constraints related to the control points: it must pass through these points and its normal and curvature may be imposed over these points. Consequently, the neural network is trained to comply with these constraints. The type of network considered so far is a multilayer feedforward neural network with two internal layers. The learning techniques (for finding relevant values of the connection weights) on which we are currently working are an expanded version of the backpropagation algorithm and a genetic algorithm. This paper lays the basis of the neural network modeling approach. Some directions for further development are also indicated.
{"title":"Modeling an isosurface with a neural network","authors":"Manuel Carcenac, A. Acan","doi":"10.1109/PCCGA.2000.883938","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883938","url":null,"abstract":"Presents a novel method for modeling an isosurface that is defined by an unstructured set of control points. The principle is to model the scalar field underlying the isosurface with a neural network: the inputs of the neural network are the three coordinates of a point in space, and its output is the value of the scalar field at this point. The isosurface is requested to satisfy some constraints related to the control points: it must pass through these points and its normal and curvature may be imposed over these points. Consequently, the neural network is trained to comply with these constraints. The type of network considered so far is a multilayer feedforward neural network with two internal layers. The learning techniques (for finding relevant values of the connection weights) on which we are currently working are an expanded version of the backpropagation algorithm and a genetic algorithm. This paper lays the basis of the neural network modeling approach. Some directions for further development are also indicated.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125401183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883958
H. Johan, Yuichi Koiso, T. Nishita
This paper presents solutions to the feature correspondence and feature interpolation problems in image morphing. The user specifies the correspondence between the source and the target images by drawing input curves on the features of the objects. The correspondence between these curves at the finest level (pixel level) is computed by optimizing a cost function. Based on this correspondence, the input curves are approximated by using Bezier curves. We represent the Bezier curves and the connections among them by using a "dependency graph". Feature interpolation is performed by interpolating the dependency graphs using the edge-angle blending technique. We also propose methods for controlling the transition rates of the shape and the color. We implemented the proposed algorithms in our morphing system which is based on the field morphing technique. From experimental results, our algorithms can generate a smooth morphing animation even when the objects in the source and the target images have different orientations. Also, the user's workload is reduced because the system includes an automatic feature correspondence computation.
{"title":"Morphing using curves and shape interpolation techniques","authors":"H. Johan, Yuichi Koiso, T. Nishita","doi":"10.1109/PCCGA.2000.883958","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883958","url":null,"abstract":"This paper presents solutions to the feature correspondence and feature interpolation problems in image morphing. The user specifies the correspondence between the source and the target images by drawing input curves on the features of the objects. The correspondence between these curves at the finest level (pixel level) is computed by optimizing a cost function. Based on this correspondence, the input curves are approximated by using Bezier curves. We represent the Bezier curves and the connections among them by using a \"dependency graph\". Feature interpolation is performed by interpolating the dependency graphs using the edge-angle blending technique. We also propose methods for controlling the transition rates of the shape and the color. We implemented the proposed algorithms in our morphing system which is based on the field morphing technique. From experimental results, our algorithms can generate a smooth morphing animation even when the objects in the source and the target images have different orientations. Also, the user's workload is reduced because the system includes an automatic feature correspondence computation.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123752325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-10-03DOI: 10.1109/PCCGA.2000.883945
Eung-Seok Lee, Hyeongseok Ko
In the field of geometry compression, two main compression targets exist. One is triangle connectivity data and the other is vertex position data. The authors propose a novel algorithm to compress the vertex data. A fundamentally different approach taken in the paper is to transform the vertex positions to the model space, a coordinate system formed by the three previously processed vertices. Once all the vertices are transformed, we found that the result shows a strong tendency to cluster around three points. We exploit such a tendency during the vector quantization steps to increase the compression ratio. According to the experiments performed on 12 models, the average compression performance of our algorithm is 6.7 bits/vertex, which is a clear improvement over previous methods.
{"title":"Vertex data compression for triangular meshes","authors":"Eung-Seok Lee, Hyeongseok Ko","doi":"10.1109/PCCGA.2000.883945","DOIUrl":"https://doi.org/10.1109/PCCGA.2000.883945","url":null,"abstract":"In the field of geometry compression, two main compression targets exist. One is triangle connectivity data and the other is vertex position data. The authors propose a novel algorithm to compress the vertex data. A fundamentally different approach taken in the paper is to transform the vertex positions to the model space, a coordinate system formed by the three previously processed vertices. Once all the vertices are transformed, we found that the result shows a strong tendency to cluster around three points. We exploit such a tendency during the vector quantization steps to increase the compression ratio. According to the experiments performed on 12 models, the average compression performance of our algorithm is 6.7 bits/vertex, which is a clear improvement over previous methods.","PeriodicalId":342067,"journal":{"name":"Proceedings the Eighth Pacific Conference on Computer Graphics and Applications","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131979504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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