We formulate contour correspondence as a Quadratic Assignment Problem (QAP), incorporating proximity information. By maintaining the neighborhood relation between points this way, we show that better matching results are obtained in practice. We propose the first Ant Colony Optimization (ACO) algorithm specifically aimed at solving the QAP-based shape correspondence problem. Our ACO framework is flexible in the sense that it can handle general point correspondence, but also allows extensions, such as order preservation, for the more specialized contour matching problem. Various experiments are presented which demonstrate that this approach yields high-quality correspondence results and is computationally efficient when compared to other methods.
{"title":"Contour Correspondence via Ant Colony Optimization","authors":"O. V. Kaick, G. Hamarneh, Hao Zhang, P. Wighton","doi":"10.1109/PG.2007.56","DOIUrl":"https://doi.org/10.1109/PG.2007.56","url":null,"abstract":"We formulate contour correspondence as a Quadratic Assignment Problem (QAP), incorporating proximity information. By maintaining the neighborhood relation between points this way, we show that better matching results are obtained in practice. We propose the first Ant Colony Optimization (ACO) algorithm specifically aimed at solving the QAP-based shape correspondence problem. Our ACO framework is flexible in the sense that it can handle general point correspondence, but also allows extensions, such as order preservation, for the more specialized contour matching problem. Various experiments are presented which demonstrate that this approach yields high-quality correspondence results and is computationally efficient when compared to other methods.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"142 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116579184","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}
We propose a technique for fusing a bracketed exposure sequence into a high quality image, without converting to HDR first. Skipping the physically-based HDR assembly step simplifies the acquisition pipeline. This avoids camera response curve calibration and is computationally efficient. It also allows for including flash images in the sequence. Our technique blends multiple exposures, guided by simple quality measures like saturation and contrast. This is done in a multiresolution fashion to account for the brightness variation in the sequence. The resulting image quality is comparable to existing tone mapping operators.
{"title":"Exposure Fusion","authors":"T. Mertens, J. Kautz, F. Reeth","doi":"10.1109/PG.2007.17","DOIUrl":"https://doi.org/10.1109/PG.2007.17","url":null,"abstract":"We propose a technique for fusing a bracketed exposure sequence into a high quality image, without converting to HDR first. Skipping the physically-based HDR assembly step simplifies the acquisition pipeline. This avoids camera response curve calibration and is computationally efficient. It also allows for including flash images in the sequence. Our technique blends multiple exposures, guided by simple quality measures like saturation and contrast. This is done in a multiresolution fashion to account for the brightness variation in the sequence. The resulting image quality is comparable to existing tone mapping operators.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122721601","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}
Efficient numerical techniques developed in the field of computer graphics are able to simulate compellingly realistic simulations of interactions between solids and fluids. These techniques are less used for engineering applications due to errors inherent in the systemic approximations. The errors, manifesting as excessive damping, are expected to change the nature of steady-state fields and nullify the typical engineering static flow analysis. On the other hand, near-body solid/fluids interaction are affected to a lesser degree since errors originating from dissipation are more severe when accumulated over time. Although it is generally not possible to numerically validate unsteady, high-velocity vector fields, our investigations show that near- body solid/fluid dynamics converges with respect to parametric refinements. Though far from a correctness proof, the numerical convergence of near-body quantities suggests the applicability of the method to certain classes of analysis and visualization where near-body characteristics are of greater concern. This article applies the semi-Lagrangian stable fluids method to biomechanical hydrodynamics visualization. The near-body surface dynamics provide meaningful information for rendering visuals that are intuitive to the streamlined flow characteristics surrounding the body. The techniques are applied to the visualization of active and passive resistive forces on the body in a video-based capture of an immersed dolphin kick.
{"title":"Visualization and Simulation of Near-Body Hydrodynamics Using the Semi-Lagrangian Fluid Simulation Method","authors":"Duc-Thang Truong, Y. Chow, A. Fang","doi":"10.1109/PG.2007.58","DOIUrl":"https://doi.org/10.1109/PG.2007.58","url":null,"abstract":"Efficient numerical techniques developed in the field of computer graphics are able to simulate compellingly realistic simulations of interactions between solids and fluids. These techniques are less used for engineering applications due to errors inherent in the systemic approximations. The errors, manifesting as excessive damping, are expected to change the nature of steady-state fields and nullify the typical engineering static flow analysis. On the other hand, near-body solid/fluids interaction are affected to a lesser degree since errors originating from dissipation are more severe when accumulated over time. Although it is generally not possible to numerically validate unsteady, high-velocity vector fields, our investigations show that near- body solid/fluid dynamics converges with respect to parametric refinements. Though far from a correctness proof, the numerical convergence of near-body quantities suggests the applicability of the method to certain classes of analysis and visualization where near-body characteristics are of greater concern. This article applies the semi-Lagrangian stable fluids method to biomechanical hydrodynamics visualization. The near-body surface dynamics provide meaningful information for rendering visuals that are intuitive to the streamlined flow characteristics surrounding the body. The techniques are applied to the visualization of active and passive resistive forces on the body in a video-based capture of an immersed dolphin kick.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128478106","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}
In this paper, we describe a method for exact evaluation of a limit mesh defined via subdivision on a uniform grid of any size. Other exact evaluation technique either restrict the grids to have subdivision sampling and are, hence, exponentially increasing in size or make assumptions about the underlying surface being piecewise polynomial (Stam's method is a widely used technique that makes this assumption). As opposed to Stam's technique, our method works for both polynomial and non-polynomial schemes. The values for this exact evaluation scheme can be computed via a simple system of linear equation derived from the scaling relations associated with the scheme or, equivalently, as the dominant left eigenvector of an upsampled subdivision matrix associated with the scheme. To illustrate one possible application of this method, we demonstrate how to generate adaptive polygonalizations of a non-polynomial quad-based subdivision surfaces using our exact evaluation method. Our method guarantees a water-tight tessellation no matter how the surface is sampled and is quite fast. We achieve tessellation rates of over 33.5 million triangles/ second using a CPU implementation.
{"title":"Exact Evaluation of Non-Polynomial Subdivision Schemes at Rational Parameter Values","authors":"S. Schaefer, J. Warren","doi":"10.1109/PG.2007.8","DOIUrl":"https://doi.org/10.1109/PG.2007.8","url":null,"abstract":"In this paper, we describe a method for exact evaluation of a limit mesh defined via subdivision on a uniform grid of any size. Other exact evaluation technique either restrict the grids to have subdivision sampling and are, hence, exponentially increasing in size or make assumptions about the underlying surface being piecewise polynomial (Stam's method is a widely used technique that makes this assumption). As opposed to Stam's technique, our method works for both polynomial and non-polynomial schemes. The values for this exact evaluation scheme can be computed via a simple system of linear equation derived from the scaling relations associated with the scheme or, equivalently, as the dominant left eigenvector of an upsampled subdivision matrix associated with the scheme. To illustrate one possible application of this method, we demonstrate how to generate adaptive polygonalizations of a non-polynomial quad-based subdivision surfaces using our exact evaluation method. Our method guarantees a water-tight tessellation no matter how the surface is sampled and is quite fast. We achieve tessellation rates of over 33.5 million triangles/ second using a CPU implementation.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116365013","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}
In this paper, we present a new and efficient spherical harmonics decomposition for spherical functions defining 3D triangulated objects. Such spherical functions are intrinsically associated to star-shaped objects. However, our results can be extended to any triangular object after segmentation into star-shaped surface patches and recomposition of the results in the implicit framework. There is thus no restriction about the genus number of the object. We demonstrate that the evaluation of the spherical harmonics coefficients can be performed by a Monte Carlo integration over the edges, which makes the computation more accurate and faster than previous techniques, and provides a better control over the precision error in contrast to the voxel-based methods. We present several applications of our research, including fast spectral surface reconstruction from point clouds, local surface smoothing and interactive geometric texture transfer.
{"title":"Efficient Spherical Harmonics Representation of 3D Objects","authors":"M. Mousa, R. Chaine, S. Akkouche, Eric Galin","doi":"10.1109/PG.2007.39","DOIUrl":"https://doi.org/10.1109/PG.2007.39","url":null,"abstract":"In this paper, we present a new and efficient spherical harmonics decomposition for spherical functions defining 3D triangulated objects. Such spherical functions are intrinsically associated to star-shaped objects. However, our results can be extended to any triangular object after segmentation into star-shaped surface patches and recomposition of the results in the implicit framework. There is thus no restriction about the genus number of the object. We demonstrate that the evaluation of the spherical harmonics coefficients can be performed by a Monte Carlo integration over the edges, which makes the computation more accurate and faster than previous techniques, and provides a better control over the precision error in contrast to the voxel-based methods. We present several applications of our research, including fast spectral surface reconstruction from point clouds, local surface smoothing and interactive geometric texture transfer.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121728650","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}
The craft of papercutting is part of the folk art traditions of cultures all over the world. From the point of view of computer graphics, papercutting can be seen as a method of composing bi-level images under a set of geometric connectivity constraints. In this paper, we present a technique for composing digital paper-cut designs. The elements of a design may be images, which are processed via a multilayer thresholding operation, or they may be procedurallygenerated arrangements of shapes. Elements are composed using a set of boolean operators that preserve connectivity. The resulting designs are well suited to being cut by a new generation of inexpensive computer peripherals.
{"title":"Computer-Generated Papercutting","authors":"Jie Xu, C. Kaplan, Xiaofeng Mi","doi":"10.1109/PG.2007.10","DOIUrl":"https://doi.org/10.1109/PG.2007.10","url":null,"abstract":"The craft of papercutting is part of the folk art traditions of cultures all over the world. From the point of view of computer graphics, papercutting can be seen as a method of composing bi-level images under a set of geometric connectivity constraints. In this paper, we present a technique for composing digital paper-cut designs. The elements of a design may be images, which are processed via a multilayer thresholding operation, or they may be procedurallygenerated arrangements of shapes. Elements are composed using a set of boolean operators that preserve connectivity. The resulting designs are well suited to being cut by a new generation of inexpensive computer peripherals.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127966418","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}
We consider the problem of generating a map between two triangulated meshes, M and M', with arbitrary and possibly differing genus. This problem has rarely been tackled in its generality. Early schemes considered only topological spheres. Recent algorithms allow inputs with an arbitrary number of tunnels but require M and M' to have equal genus, mapping tunnel to tunnel. Other schemes which allow more general inputs are not guaranteed to work and the authors do not provide a characterization of the input meshes that can be processed successfully. Moreover, the techniques have difficulty dealing with coarse meshes with many tunnels. In this paper we present the first robust approach to build a map between two meshes of arbitrary unequal genus. We also provide a simplified method for setting the initial alignment between M and M', reducing reliance on landmarks and allowing the user to select "landmark tunnels" in addition to the standard landmark vertices. After computing the map, we automatically derive a continuous deformation from M to M' using a variational implicit approach to describe the evolution of non-landmark tunnels. Overall, we achieve a cross parameterization scheme that is provably robust in the sense that it can mapM toM' without constraints on their relative genus or on the density of the triangulation with respect to the number of tunnels. To demonstrate the practical effectiveness of our scheme we provide a number of examples of inter-surface parameterizations between meshes of different genus and shape.
{"title":"Genus Oblivious Cross Parameterization: Robust Topological Management of Inter-Surface Maps","authors":"Janine Bennett, Valerio Pascucci, K. Joy","doi":"10.1109/PG.2007.42","DOIUrl":"https://doi.org/10.1109/PG.2007.42","url":null,"abstract":"We consider the problem of generating a map between two triangulated meshes, M and M', with arbitrary and possibly differing genus. This problem has rarely been tackled in its generality. Early schemes considered only topological spheres. Recent algorithms allow inputs with an arbitrary number of tunnels but require M and M' to have equal genus, mapping tunnel to tunnel. Other schemes which allow more general inputs are not guaranteed to work and the authors do not provide a characterization of the input meshes that can be processed successfully. Moreover, the techniques have difficulty dealing with coarse meshes with many tunnels. In this paper we present the first robust approach to build a map between two meshes of arbitrary unequal genus. We also provide a simplified method for setting the initial alignment between M and M', reducing reliance on landmarks and allowing the user to select \"landmark tunnels\" in addition to the standard landmark vertices. After computing the map, we automatically derive a continuous deformation from M to M' using a variational implicit approach to describe the evolution of non-landmark tunnels. Overall, we achieve a cross parameterization scheme that is provably robust in the sense that it can mapM toM' without constraints on their relative genus or on the density of the triangulation with respect to the number of tunnels. To demonstrate the practical effectiveness of our scheme we provide a number of examples of inter-surface parameterizations between meshes of different genus and shape.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"1987 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125476010","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}
We describe a new algorithm for the visualisation of implicit algebraic curves, which isolates the singular points, compute the topological degree around these points in order to check that the topology of the curve can be deduced from the points on the boundary of these singular regions. The other regions are divided into x or y regular regions, in which the branches of the curve are also determined from information on the boundary. Combined with enveloping techniques of the polynomial represented in the Bernstein basis, it is shown on examples that this algorithm is able to render curves defined by high degree polynomials with large coefficients, to identify regions of interest and to zoom safely on these regions.
{"title":"Visualisation of Implicit Algebraic Curves","authors":"L. Alberti, B. Mourrain","doi":"10.1109/PG.2007.32","DOIUrl":"https://doi.org/10.1109/PG.2007.32","url":null,"abstract":"We describe a new algorithm for the visualisation of implicit algebraic curves, which isolates the singular points, compute the topological degree around these points in order to check that the topology of the curve can be deduced from the points on the boundary of these singular regions. The other regions are divided into x or y regular regions, in which the branches of the curve are also determined from information on the boundary. Combined with enveloping techniques of the polynomial represented in the Bernstein basis, it is shown on examples that this algorithm is able to render curves defined by high degree polynomials with large coefficients, to identify regions of interest and to zoom safely on these regions.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"276 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115600725","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}
Minkowski sum is a fundamental operation in many geometric applications, including robotics, penetration depth estimation, solid modeling, and virtual prototyping. However, due to its high computational complexity and several nontrivial implementation issues, computing the exact boundary of the Minkowski sum of two arbitrary polyhedra is generally a difficult task. In this work, we propose to represent the boundary of the Minkowski sum approximately using only points. Our results show that this point-based representation can be generated efficiently. An important feature of our method is its straightforward implementation and parallelization. We also demonstrate that the point-based representation of the Minkowski sum boundary can indeed provide similar functionality as mesh-based representations can. We show several applications in motion planning, penetration depth approximation and modeling.
{"title":"Point-Based Minkowski Sum Boundary","authors":"Jyh-Ming Lien","doi":"10.1109/PG.2007.49","DOIUrl":"https://doi.org/10.1109/PG.2007.49","url":null,"abstract":"Minkowski sum is a fundamental operation in many geometric applications, including robotics, penetration depth estimation, solid modeling, and virtual prototyping. However, due to its high computational complexity and several nontrivial implementation issues, computing the exact boundary of the Minkowski sum of two arbitrary polyhedra is generally a difficult task. In this work, we propose to represent the boundary of the Minkowski sum approximately using only points. Our results show that this point-based representation can be generated efficiently. An important feature of our method is its straightforward implementation and parallelization. We also demonstrate that the point-based representation of the Minkowski sum boundary can indeed provide similar functionality as mesh-based representations can. We show several applications in motion planning, penetration depth approximation and modeling.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123200737","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}
The faceting signal, defined in this paper as the difference signal between a rendering of the original geometric model and a simplified version of the geometric model, is responsible for the faceting artifacts commonly observed in the renderings of coarse geometric models. In this paper, we analyze the source of the faceting signal and develop a perceptual metric for the visibility of the faceting signal.
{"title":"Faceting Artifact Analysis for Computer Graphics","authors":"Lijun Qu, G. Meyer","doi":"10.1109/PG.2007.61","DOIUrl":"https://doi.org/10.1109/PG.2007.61","url":null,"abstract":"The faceting signal, defined in this paper as the difference signal between a rendering of the original geometric model and a simplified version of the geometric model, is responsible for the faceting artifacts commonly observed in the renderings of coarse geometric models. In this paper, we analyze the source of the faceting signal and develop a perceptual metric for the visibility of the faceting signal.","PeriodicalId":376934,"journal":{"name":"15th Pacific Conference on Computer Graphics and Applications (PG'07)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123909067","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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