Results 11  20
of
94
Centroidal Voronoi Tesselation of Line Segments and Graphs
"... Figure 1: Starting from a mesh (A) and a template skeleton (B), our method fits the skeleton to the mesh (C) and outputs a segmentation (D). Our main contribution is an extension of Centroidal Voronoi Tesselation to line segments, using approximated Voronoi Diagrams of segments (E). Segment Voronoi ..."
Abstract

Cited by 13 (0 self)
 Add to MetaCart
(Show Context)
Figure 1: Starting from a mesh (A) and a template skeleton (B), our method fits the skeleton to the mesh (C) and outputs a segmentation (D). Our main contribution is an extension of Centroidal Voronoi Tesselation to line segments, using approximated Voronoi Diagrams of segments (E). Segment Voronoi cells (colors) are approximated by the union of sampled point’s Voronoi cells (thin lines, right half of D). Clipped 3D Voronoi cells are accurately computed, at a subfacet precision (F). Centroidal Voronoi Tesselation (CVT) of points has many applications in geometry processing, including remeshing and segmentation to name but a few. In this paper, we propose a new extension of CVT, generalized to graphs. Given a graph and a 3D polygonal surface, our method optimizes the placement of the vertices of the graph in such a way that the graph segments best approximate the shape of the surface. We formulate the computation of CVT for graphs as a continuous variational problem, and present a simple approximated method to solve this problem. Our method is robust in the sense that it is independent of degeneracies in the input mesh, such as skinny triangles, Tjunctions, small gaps or multiple connected components. We present some applications, to skeleton fitting and to shape segmentation.
Continuations and transducer composition
 In PLDI ’06
, 2006
"... Online transducers are an important class of computational agent; we construct and compose together many software systems using them, such as stream processors, layered network protocols, DSP networks and graphics pipelines. We show an interesting use of continuations, that, when taken in a CPS set ..."
Abstract

Cited by 10 (6 self)
 Add to MetaCart
Online transducers are an important class of computational agent; we construct and compose together many software systems using them, such as stream processors, layered network protocols, DSP networks and graphics pipelines. We show an interesting use of continuations, that, when taken in a CPS setting, exposes the control flow of these systems. This enables a CPSbased compiler to optimise systems composed of these transducers, using only standard, known analyses and optimisations. Critically, the analysis permits optimisation across the composition of these transducers, allowing efficient construction of systems in a hierarchical way.
Misregistration sensitivity in clustereddot color halftones
 JOURNAL OF ELECTRONIC IMAGING 17(2), 023004 (APR–JUN 2008)
, 2008
"... Halftoned separations of individual colorants, typically cyan, magenta, yellow, and black, are overlaid on a print substrate in typical color printing systems. Displacements between these separations, commonly referred to as “interseparation misregistration”, can cause objectionable color shifts i ..."
Abstract

Cited by 10 (5 self)
 Add to MetaCart
Halftoned separations of individual colorants, typically cyan, magenta, yellow, and black, are overlaid on a print substrate in typical color printing systems. Displacements between these separations, commonly referred to as “interseparation misregistration”, can cause objectionable color shifts in the prints. We study this misregistrationinduced color shift for periodic clustereddot halftones using a spatiospectral model for the printed output that combines the Neugebauer model with a periodic lattice representation for the individual halftones. Using Fourier analysis in the framework of this model, we obtain an analytic characterization for the conditions for misregistration invariance in terms of colorant spectra, periodicity of the individual separation halftones, dot shapes, and misregistration displacements. We further exploit the framework in a hybrid analyticalnumerical simulation that allows us to obtain quantitative estimates of the color shifts due to misregistration, thereby providing a characterization for these shifts as a function of the optical dot gain, halftone periodicities, spot shapes, and interseparation misregistration amounts. We present simulation results that demonstrate the impact of each of these parameters on the color shift and demonstrate qualitative agreement between our approximation and experimental data.
Clipping Using Homogeneous Coordinates
 Proceedings of SIGGRAPH ’78
, 1978
"... Clipping is the process of determining how much of a given line segment lies within the boundaries of the display screen. Homogeneous coordinates are a convenient mathematical device for representing and transforming objects. The space represented by homogeneous coordinates is not, however, a simple ..."
Abstract

Cited by 10 (0 self)
 Add to MetaCart
(Show Context)
Clipping is the process of determining how much of a given line segment lies within the boundaries of the display screen. Homogeneous coordinates are a convenient mathematical device for representing and transforming objects. The space represented by homogeneous coordinates is not, however, a simple Euclidean 3space. It is, in fact, analagous to a topological shape called a "projective plane". The clipping problem is usually solved without consideration for the differences between Euclidean space and the space represented by homogeneous coordinates. For some constructions, this leads to errors in picture generation which show up as lines marked invisible when they should be visible. This paper will examine these cases and present techniques for correctly clipping the line segments. 1.
Efficient computation of 3d clipped voronoi diagram
 In GMP conf. proc
, 2010
"... Abstract. The Voronoi diagram is a fundamental geometry structure widely used in various fields, especially in computer graphics and geometry computing. For a set of points in a compact 3D domain (i.e. a finite 3D volume), some Voronoi cells of their Voronoi diagram are infinite, but in practice onl ..."
Abstract

Cited by 7 (3 self)
 Add to MetaCart
(Show Context)
Abstract. The Voronoi diagram is a fundamental geometry structure widely used in various fields, especially in computer graphics and geometry computing. For a set of points in a compact 3D domain (i.e. a finite 3D volume), some Voronoi cells of their Voronoi diagram are infinite, but in practice only the parts of the cells inside the domain are needed, as when computing the centroidal Voronoi tessellation. Such a Voronoi diagram confined to a compact domain is called a clipped Voronoi diagram. We present an efficient algorithm for computing the clipped Voronoi diagram for a set of sites with respect to a compact 3D volume, assuming that the volume is represented as a tetrahedral mesh. We also describe an application of the proposed method to implementing a fast method for optimal tetrahedral mesh generation based on the centroidal Voronoi tessellation.
SIMPLIFIED LINEARTIME JORDAN SORTING AND POLYGON CLIPPING
, 1990
"... Given the intersection points of a Jordan curve with the xaxis in the order in which they occur along the curve, the Jordan sorting problem is to sort them into the order in which they occur along the xaxis. This problem arises in clipping a simple polygon against a rectangle (a “window”) and in e ..."
Abstract

Cited by 7 (1 self)
 Add to MetaCart
Given the intersection points of a Jordan curve with the xaxis in the order in which they occur along the curve, the Jordan sorting problem is to sort them into the order in which they occur along the xaxis. This problem arises in clipping a simple polygon against a rectangle (a “window”) and in efficient algorithms for triangulating a simple polygon. Hoffman, Mehlhorn, Rosenstiehl, and Tarjan proposed an algorithm that solves the Jordan sorting problem in time that is linear in the number of intersection points, but their algorithm requires the use of a sophisticated data structure, the levellinked search tree. We propose a variant of the algorithm of Hoffman et al. that retains the lineartime bound but simplifies both the primary data structure and the operations it must perform.
SmoothnessIncreasing AccuracyConserving (SIAC) Filtering for Discontinuous Galerkin Solutions: Improved Errors Versus HigherOrder Accuracy
, 2012
"... © The Author(s) 2012. This article is published with open access at Springerlink.com Abstract Smoothnessincreasing accuracyconserving (SIAC) filtering has demonstrated its effectiveness in raising the convergence rate of discontinuous Galerkin solutions from order k + 1 to order 2k + 1 for specifi ..."
Abstract

Cited by 7 (4 self)
 Add to MetaCart
(Show Context)
© The Author(s) 2012. This article is published with open access at Springerlink.com Abstract Smoothnessincreasing accuracyconserving (SIAC) filtering has demonstrated its effectiveness in raising the convergence rate of discontinuous Galerkin solutions from order k + 1 to order 2k + 1 for specific types of translation invariant meshes (Cockburn et 2
SMOOTHNESSINCREASING ACCURACYCONSERVING (SIAC) POSTPROCESSING FOR DISCONTINUOUS GALERKIN SOLUTIONS OVER STRUCTURED TRIANGULAR MESHES ∗
, 1899
"... Abstract. Theoretically and computationally, it is possible to demonstrate that the order of accuracy of a discontinuous Galerkin (DG) solution for linear hyperbolic equations can be improved from order k+1 to 2k+1 through the use of smoothnessincreasing accuracyconserving (SIAC) filtering. Howeve ..."
Abstract

Cited by 7 (3 self)
 Add to MetaCart
(Show Context)
Abstract. Theoretically and computationally, it is possible to demonstrate that the order of accuracy of a discontinuous Galerkin (DG) solution for linear hyperbolic equations can be improved from order k+1 to 2k+1 through the use of smoothnessincreasing accuracyconserving (SIAC) filtering. However, it is a computationally complex task to perform this in an efficient manner, which becomes an even greater issue considering nonquadrilateral mesh structures. In this paper, we present an extension of this SIAC filter to structured triangular meshes. The basic theoretical assumption in the previous implementations of the postprocessor limits the use to numerical solutions solved over a quadrilateral mesh. However, this assumption is restrictive, which in turn complicates the application of this postprocessing technique to general tessellations. Additionally, moving from quadrilateral meshes to triangulated ones introduces more complexity in the calculations as the number of integrations required increases. In this paper, we extend the current theoretical results to variable coefficient hyperbolic equations over structured triangular meshes and demonstrate the effectiveness of the application of this postprocessor to structured triangular meshes as well as exploring the effect of using inexact quadrature. We show that there is a direct theoretical extension to structured triangular meshes for hyperbolic equations with bounded variable coefficients. This is a challenging first step toward implementing SIAC filters for unstructured tessellations. We show that by using the usual Bspline implementation, we are able to improve on the order of accuracy as well as decrease the magnitude of the errors. These results are valid regardless of whether exact or inexact integration is used. The results here demonstrate that it is still possible, both theoretically and computationally, to improve to 2k+1 over the DG solution itself for structured triangular meshes.
Parallel Rendering Techniques for Multiprocessor Systems
 Comenius University Bratislava
, 1994
"... This paper presents the stateoftheart parallel rendering techniques for interpolation shading, raytracing and radiosity. In addition the most sophisticated parallel architectures for real time rendering are introduced. The new Virtual Walls concept especially designed for asyncronously distribute ..."
Abstract

Cited by 6 (1 self)
 Add to MetaCart
(Show Context)
This paper presents the stateoftheart parallel rendering techniques for interpolation shading, raytracing and radiosity. In addition the most sophisticated parallel architectures for real time rendering are introduced. The new Virtual Walls concept especially designed for asyncronously distributed multiprocessor systems is presented by the author. It describes new distributed rendering techniques based on spatial subdivision and has already been implemented on massively parallel transputer systems and on networks of workstations. Keywords: Parallel, Rendering, Raytracing, Radiosity. 1 Introduction Parallel rendering techniques is a field whose time has come. Until recently for the most it was an cumbersome specialty involving complicated and expensive hardware. In addition the programmers of distributed software had to begin to think parallel. In the last few years, however, there has been a steady and sometimes even spectacular reduction in the hardware price/performance ratio an...
Threedimensional computer graphics. A coordinatefree approach
, 1992
"... 2.1 Scanconverting Line Segments............. 8 ..."
(Show Context)