Andrej Ferko

Multicriteria-optimized triangulations

Triangulation of a given set of points in a plane is one of the most commonly solved problems in computer graphics and computational geometry. Because they are useful in many applications, triangulations must provide well-shaped triangles. Many criteria have been developed to provide such meshes, namely weight and angular criteria. Each criterion has its pros and cons, some of them are difficult to compute, and sometimes even the polynomial algorithm is not known. By any of the existing deterministic methods, it is not possible to compute a triangulation which satisfies more than one criterion or which contains parts developed according to several criteria. We explain how such a mixture can be generated using genetic optimization.

Feature-preserving mesh denoising via attenuated bilateral normal filtering and quadrics

In this paper, we propose a two phase feature-preserving mesh denoising algorithm. The first phase consists of modified bilateral filtering applied on field of face normals. The range filtering is affected by gradual attenuation of the standard deviation of normal differences along with subsequent iteration. We also provide a method for automatic estimation of the bilateral filter parameters without user interaction. Filtering process is followed by reconstruction of the mesh vertex positions from a given field of face normals. Our method is based on geometric fact that every vertex should lie within all tangent planes that locally support one of its neighbouring triangles. We use quadrics to encode squared distances to the planes defined by filtered normals and centroids of the faces from 1-ring neighbourhood of considered vertex. New vertex positions are identified by minimizing quadric error metric. Our tests have shown that this iteration scheme converges faster than gradient descent algorithm. Sharp features are well preserved which will be documented on several CAD-like models.

Beyond Image Quality Comparison

We solve the problem of quantitative measuring of image quality, beyond the widely used MSE (mean square error) or even visual comparison. We combine eight feature-based and perceptually-oriented image quality metrics. The need for this comes from virtual archaeology, where various image acquisitions, antialiasing, multiresolution, image reconstruction or texturing methods produce very similar images. The proposed evaluation framework is suitable for any image quality decision-making, being not restricted to virtual archaeology. In particular, we compare a representative database of visually indistiguishable image pairs from different cameras, anisotropic texture filters and various antialiasing methods. For image registration we propose a modified video processing step. The results support the selection beyond commonly used visual comparison.

Technical Section: Parallel GPU-based data-dependent triangulations

In this paper we introduce a new technique for data-dependent triangulation which is suitable for implementation on a GPU. Our solution is based on a new parallel version of the well known Lawsons optimization process and is fully compatible with restrictions of the GPU hardware. We test and compare the quality of our solution in an image reconstruction problem. In comparison with the standard implementations we achieve significant speed-up (eight times on average) with comparable quality of the reconstructed image. Further, several other improvements and optimizations are introduced and tested, and the results are discussed in detail.

Distinctive Approaches to Computer Graphics Education

This paper presents the latest advances and research in Computer Graphics education in a nutshell. It is concerned with topics that were presented at the Education Track of the Eurographics Conference held in Lisbon in 2016. We describe works corresponding to approaches to Computer Graphics education that are unconventional in some way and attempt to tackle unsolved problems and challenges regarding the role of arts in computer graphics education, the role of research‐oriented activities in undergraduate education and the interaction among different areas of Computer Graphics, as well as their application to courses or extra‐curricular activities. We present related works addressing these topics and report experiences, successes and issues in implementing the approaches.

Distinctive Approaches to Computer Graphics Education: Distinctive Approaches to Computer Graphics Education

This paper presents the latest advances and research in Computer Graphics education in a nutshell. It is concerned with topics that were presented at the Education Track of the Eurographics Conference held in Lisbon in 2016. We describe works corresponding to approaches to Computer Graphics education that are unconventional in some way and attempt to tackle unsolved problems and challenges regarding the role of arts in computer graphics education, the role of research‐oriented activities in undergraduate education and the interaction among different areas of Computer Graphics, as well as their application to courses or extra‐curricular activities. We present related works addressing these topics and report experiences, successes and issues in implementing the approaches.

Nearest Neighbour Graph and Locally Minimal Triangulation

Nearest neighbour graph (NNG) is a useful tool namely for collision detection tests. It is well known that NNG, when considered as an undirected graph, is a subgraph of Delaunay triangulation (DT) and this relation can be used for efficient NNG computation. This paper concentrates on relation of NNG to the locally minimal triangulation (LMT) and shows that, although NNG can be proved not to be a LMT subgraph, in most cases LMT contains all or nearly all NNG edges. This fact can also be used for NNG computation, namely in kinetic problems, because LMT computation is easier.

A piece of peace in sWARajevo: Locally and globally interesting stories for virtual museums

Summary form only given. We present a method how to create locally and globally interesting stories for virtual museums in a relatively short time. The local interestingness is understood in a Koestlerian way (AH, AHA, HAHA bisociation effects). Global interestingness is achieved by discovering, within the given unique material, options for relating unrelated contexts, internal poetry and/or change of the narration mode. The craft of storytelling resulted in five short movies, completed during the South-East European Virtual Heritage School: Digital Storytelling for Virtual Museums. These intereStories“ are intentionally aimed at overcoming multiple limitations of backtelling, frequent in virtual museums. The five themes include Bosnian blues Sevdah, fate of Sephardic Jews, existing and nonexisting urban area, and traditional Bosnian coffee. The stories were coauthored by 15 beginners storytellers in groups (24 authors) in 5 days alongside with the 12 lectures on theory and narrative case studies from V-must network good practice. Besides the brainstormings, speed-up focused brainwritting feedback was provided twice: once for preexistent stories, second for betaversions. The final creations were produced in Adobe Premiere Pro and published at YouTube.

Schola ludus, serious games, and measurement of interestingness

We propose a novel engagement measurement (establihed originally in virtual museum theory) for serious games. The key idea is to measure the user input in terms of time spent. The output is given by the recorded user behavior. We discuss the implications for edutainment, e-learning, and serious games.

Texture Minification using Quad-trees and Fipmaps

The paper extends the recently published methods for image reconstruction and texture minification using the generalized ripmap method, named fipmap, and quad-trees. Fipmap is based on the technique of partitioned iterated function systems, used in fractal image compression. The quad-tree texture reconstruction algorithm works well for many standard cases. The special cases can be solved using the fipmap minification. The approach was applied for textures from architectural image sequences and the results are very promising.