Papers by Ivana Kolingerová
The paper shows a simple technique which saves some edge tests in the walking algorithm for point... more The paper shows a simple technique which saves some edge tests in the walking algorithm for point location. The walking technique does not achieve the logarithmic per point complexity of the location-datastructure-based methods but does not need any auxiliary data structure and is very simple to implement, therefore, it is very popular in practice. The suggested idea did not bring a substantial improvement in our tests but it is very simple and there is an open door to further more substantial improvement in the future research.
A cell-based point-in-polygon algorithm suitable for large sets of points
Computers & Geosciences, 2001
The paper describes a new algorithm for solving the point-in-polygon problem. It is especially su... more The paper describes a new algorithm for solving the point-in-polygon problem. It is especially suitable when it is necessary to check whether many points are placed inside or outside a polygon. The algorithm works in two steps. First, a grid of cells equal in size is generated, and the polygon is laid on that grid. A heuristic approach is proposed
Fast Delaunay Stripification (DRAFT)
2D and,2.5D triangulations,belong,nowadays,among,the most,often types of geometric,object descrip... more 2D and,2.5D triangulations,belong,nowadays,among,the most,often types of geometric,object description in computer graphics. A frequent application is, e.g., terrain modeling. Therefore the problem,of fast visualization of this type of data is often solved. One possible approach,is the reduction,of data duplicities by using triangle strips. This paper describes a new stripification algorithm for models, based on Delaunay trian- gulation using incremental insertion
Quadrilateral models,are becoming,very popular,in many,applications,of computer,graphics (e.g. co... more Quadrilateral models,are becoming,very popular,in many,applications,of computer,graphics (e.g. computer animation, computer games, scientific visualization of volumetric data, etc.). The complexity of these models can be very high (even millions of quadrilaterals), thus the problem of fast visualization of these meshes,is often being solved. To increase the speed,one can use some techniques to avoid sending of unnecessary faces (e.g., visibility culling)
Surface Reconstruction from Large Point Clouds Using Virtual Shared Memory Manager
Lecture Notes in Computer Science, 2006
ABSTRACT Surface reconstruction is a common problem in computer graphics. Given a set of points s... more ABSTRACT Surface reconstruction is a common problem in computer graphics. Given a set of points sampled from some surface, a triangle mesh interpolating or approximating the points is to be obtained. One of very often used techniques for solving this problem is the selection of surface triangles from the set of Delaunay tetrahedronization faces. In the case of large data, it is difficult to obtain the tetrahedronization due to its huge memory requirements. One of possible solutions is to use distributed computing. Here, we describe the newly developed VSM (Virtual Shared Memory) distributed toolkit and its utilization for the task of surface reconstruction. By our approach, we were able to process dataset having 1.4M points on 4xP4 interconnected via 100Mb Ethernet in 6 hours. About 5GB of memory was consumed during the reconstruction.
Lecture Notes in Geoinformation and Cartography, 2014
Encoding the geographic coordinates into the compact string expression is an important problem in... more Encoding the geographic coordinates into the compact string expression is an important problem in geosciences, therefore, several algorithms exist. Such a string is used for several purposes. One of the most frequent is probably its use as a part of a URL or as a hashtag of ad hoc data. An important part of spatially referenced data can be also a timestamp, but current encoding methods do not allow to encode the temporal dimension. In this chapter we propose a new encoding algorithm focused on a point data expressed by latitude, longitude and timestamp coordinates. The algorithm details are described and its use is shown on examples.
Parallel Delaunay triangulation based on circum-circle criterion
Proceedings of the 18th spring conference on Computer graphics - SCCG '03, 2003
This paper describes a newly proposed simple and efficient parallel algorithm for the constructio... more This paper describes a newly proposed simple and efficient parallel algorithm for the construction of the Delaunay triangulation (DT) in E2 by randomized incremental insertion. The construction of the DT is one of the fundamental problems in computer graphics. The proposed algorithm is designed for parallel systems with shared memory and several processors. Such hardware (especially with two-processors) became available
Contour lines are an important means of cartographical visualization. If computed automatically o... more Contour lines are an important means of cartographical visualization. If computed automatically on a triangulation, they contain many artefacts. This paper shows the results of their elimination by using constrained edges in the triangulation. Constrained edges can be inserted either manually by an editorwhich enables all kinds of detected artefacts to be improved manually-or automatically for some kinds of artefacts only. We present a survey of detected artefacts, evaluation of the Delaunay and greedy triangulations as to the number and kind of contour line artefacts, examples of achievements using manual placement of constrained edges and two algorithms suitable for automatic detection and removal of artefacts caused by flat triangle areas. According to our results, problems are not completely removed but the number of problematic areas is decreased substantially.
Our approach to image region approximation offers a complete scheme consisting of several steps. ... more Our approach to image region approximation offers a complete scheme consisting of several steps. We separate the encoding of region boundaries from the texture description. The original image is first segmented using an unsupervised segmentation method for colortexture regions. Following polygonal approximation of created regions causes the degradation of region boundaries. The triangulation is then applied to polygons and either all short edges, or all small triangles are filtered out from the triangular mesh. This results in new smaller regions. The encoding and decoding of polygons and triangles is very efficient, because we need to store only the vertices. For texture approximation we use 2D shape independent orthogonal transforms (e.g. DCT II). The texture is encoded with a code similar to JPEG arithmetic code. The encoding scheme proposed in this paper is much faster than latest approaches with polygonal approximation. We present the two triangulation algorithms-constrained greedy (CGT) and constrained Delaunay triangulation (CDT). Both CGT and CDT provide similar results.
Faster facility location and hierarchical clustering
ABSTRACT We propose several methods to speed up the facility location, and the single link and th... more ABSTRACT We propose several methods to speed up the facility location, and the single link and the complete link clustering algorithms. The local search algorithm for the facility location is accelerated by introducing several space partitioning methods and a parallelisation on the CPU of a standard desktop computer. The influence of the cluster size on the speedup is documented. The paper further presents the computation of the single link and the complete link clustering on the GPU using the CUDA architecture.
Regular Triangulation and Tunnels in Proteins
Proteins are organic compounds and are contained in every living cell. Protein engineering studie... more Proteins are organic compounds and are contained in every living cell. Protein engineering studies proteins and tries to modify them. For this purpose it uses (among others) an analysis of tunnels - paths, which lead from an interesting place inside a protein to its surface. In this paper the geometric approximation of tunnels in protein molecules and the application of
Multi-path algorithm for triangle strips
Proceedings Computer Graphics International, 2004., 2004
Triangle surface models belong to the most popular type of geometric objects description in compu... more Triangle surface models belong to the most popular type of geometric objects description in computer graphics. Therefore, the problem of fast visualization of this type of data is often solved. One of popular approaches is stripification, i.e., a conversion of triangle surface into strips of triangles. This enables to reduce the rendering time by reduction data size and by avoiding
The Visual Computer, 1997
Duality is a well-known principle of computational geometry. It is often used for detecting the m... more Duality is a well-known principle of computational geometry. It is often used for detecting the mutual position of convex geometrical objects, the dimensions of which do not differ more than by one; e.g., a convex polyhedron and a hyperplane or two convex polyhedra of the same dimensions. In this paper, a new possibility of usage is shown for objects with dimensions different by two. The mutual position of a convex polyhedron and a line is tested. The method works as follows. The line is described as an intersection of two planes. With a proper choice of these planes, the original problem of detecting a polyhedron-line intersection is reduced to a one-dimensional range search, which is much simpler to solve. The price to be paid for this reduction is computationally more demanding preprocessing.
The Visual Computer, 2002
The paper describes a new parallel algorithm of Delaunay triangulation based on randomized increm... more The paper describes a new parallel algorithm of Delaunay triangulation based on randomized incremental insertion. The algorithm is practical, simple and can be modified also for constrained triangulation or tetrahedralization. It was developed for architectures with a lower degree of parallelism, such as several-processor workstations, and tested on up to 8 processors.
The Visual Computer, 2001
Computers & Graphics, 2007
Triangle surface models belong to the most popular type of geometric objects description in compu... more Triangle surface models belong to the most popular type of geometric objects description in computer graphics. Therefore, the problem of fast visualization of this type of data is often solved. One popular approach is stripification, i.e., a conversion of a triangulated object surface into strips of triangles. This enables a reduction of the rendering time by reducing the data size which avoids redundant lighting and transformation computations. The problem of finding an optimal decomposition of triangle surface models to a set of strips is NP-hard and there exist a lot of different heuristic stripification techniques. This paper should help to orient in the jungle of stripification algorithms. We present an overview of existing stripification methods and detailed description of several important stripification methods for fully triangulated meshes. As different authors usually use different data sets and different architectures, it is nearly impossible to compare the quality of stripification methods. For this reason we also present a set of tests of these methods to give the reader a better possibility to compare these methods.
Computers & Geosciences, 2011
This paper presents a novel approach to handle large amounts of geometric data. A data stream clu... more This paper presents a novel approach to handle large amounts of geometric data. A data stream clustering is used to reduce the amount of data and build a hierarchy of clusters. The data stream concept allows for the processing of very large data sets. The cluster hierarchy is then used in a dynamic triangulation to create a multiresolution model. It allows for the interactive selection of a different level of detail in various parts of the data. A method for removal multiple points from Delaunay triangulation is proposed. It is significantly faster than the traditional approach. The clustering and the triangulation are supplemented by an elliptical metric to handle data with anisotropic properties. Compared to the closest competitive method by Isenburg et al., the presented algorithm requires only a single pass over the data and offers a high flexibility. These advantages culminate in a long running time. The method was tested on several large digital elevation maps. The clustering phase can take up to a few hours. Once the cluster hierarchy is built, the terrains can be efficiently manipulated in real time.
A Proper Choice of Vertices for Triangulation Representation of Digital Images
Representation of the digital image by a triangulation does not bring a high compression but enab... more Representation of the digital image by a triangulation does not bring a high compression but enables geometric transformations and is very simple. In this paper we will show that it is also possible to choose the triangulation vertices randomly, then their [x,y] position does not need to be stored as it can be easily reconstructed during decoding. We show how
Fast Method for Computation of Channels in Dynamic Proteins Session 10: Shapes
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Papers by Ivana Kolingerová