A Comparative Study on Polygonal Mesh Simplification Algorithms

Polygonal meshes are a common way of representing three dimensional surface models in many different areas of computer graphics and geometry processing. However, with the evolution of the technology, polygonal models are becoming more and more complex. As the complexity of the models increase, the visual approximation to the real world objects get better but there is a trade-off between the cost of processing these models and better visual approximation. In order to reduce this cost, the number of polygons in a model can be reduced by mesh simplification algorithms. These algorithms are widely used such that nearly all of the popular mesh editing libraries include at least one of them. In this work, polygonal simplification algorithms that are embedded in open source libraries: CGAL, VTK and OpenMesh are compared with the Metro geometric error measuring tool. By this way we try to supply a guidance for developers for publicly available mesh libraries in order to implement polygonal mesh simplification

The Development and Evolution of Digital Leadership: A Bibliometric Mapping Approach-Based Study

The inevitable digitalization of workplaces in the present era, generally as a result of technological developments, has caused a paradigm shift, along with new innovative business models and business behaviors, which has required leaders to possess certain digital skills for sustainable corporate performance. Hence, studies on digital leadership have attracted the attention of academics and practitioners worldwide, with many studies having been conducted on the topic. However, a comprehensive analysis of the intellectual architecture, knowledge structure, and thematic evolution of the digital leadership field of research using science mapping tools has yet to be conducted. The current study, therefore, aimed at reviewing the intellectual structure and evolution of the digital leadership field through a bibliometric and science-mapping analysis. This study used digital leadership as an umbrella term comprising leadership styles such as e-leadership, virtual leadership, technology leadership, and leadership 4.0, which have similar meanings and can be used interchangeably. With this purpose, bibliometric performance and science mapping analysis was performed on articles related to the research field that were retrieved from the Scopus database using SciMAT software (version 1.1.04). The results of the study revealed that the scope of digital leadership research is gradually expanding and diversifying and that publication output is increasing steadily. In addition, period-based analysis showed that the technology management theme during the first period, the virtual teams and technology themes during the second period, and the COVID-19, virtual reality, and digital technologies themes during the third period emerged as the motor themes and formed the focus of research in this field. Thematic evolution analysis showed that virtual leadership during the first and second periods, virtual teams during the second period, e-leadership and technology during the second and third periods, and digital leadership, COVID-19, and virtual reality during the third period, along with technology leadership in all three periods were all noteworthy as well-developed research themes. These findings enable a better understanding of the research field of digital leadership and provide a reference for future research by revealing the conceptual structure and thematic evolution of the digital leadership knowledge base

Arrangements 2D pour la Cartographie de l’Espace Public et des Transports

This thesis addresses easy and effective development of mapping and transportation applications which especially focuses on the generation of pedestrian networks for applications like navigation, itinerary calculation, accessibility analysis and urban planning. In order to achieve this goal, we proposed a two layered data model which encodes the public space into a hierarchy of semantic geospatial objects. At the lower level, the 2D geometry of the geospatial objects are captured using a planar partition which is represented as a topological 2D arrangement. This representation of a planar partition allows efficient and effective geometry processing and easy maintenance and validation throughout the editions when the geometry or topology of an object is modified. At the upper layer, the semantic and thematic aspects of geospatial objects are modelled and managed. The hierarchy between these objects is maintained using a directed acyclic graph (DAG) in which the leaf nodes correspond to the geometric primitives of the 2D arrangement and the higher level nodes represent the aggregated semantic geospatial objects at different levels. We integrated the proposed data model into our GIS framework called StreetMaker together with a set of generic algorithms and basic GIS capabilities. This framework is then rich enough to generate pedestrian network graphs automatically. In fact, within an accessibility analysis project, the full proposed pipeline was successfully used on two sites to produce pedestrian network graphs from various types of input data: existing GIS vector maps, semi-automatically created vector data and vector objects extracted from Mobile Mapping lidar point clouds.While modelling 2D ground surfaces may be sufficient for 2D GIS applications, 3D GIS applications require 3D models of the environment. 3D modelling is a very broad topic but as a first step to such 3D models, we focused on the semi-automatic modelling of objects which can be modelled or approximated by generalized cylinders (such as poles, lampposts, tree trunks, etc.) from single images. The developed methods and techniques are presented and discussedCette thèse porte sur le développement facilité d'applications de cartographie et de transport, plus particulièrement sur la génération de réseaux piétonniers pour des applications telles que la navigation, le calcul d'itinéraires, l'analyse d'accessibilité et l'urbanisme. Afin d'atteindre ce but, nous proposons un modèle de données à deux couches qui cartographie l'espace public dans une hiérarchie d'objets géospatiaux sémantisés. A bas niveau, la géométrie 2D des objets géospatiaux est représentée par une partition planaire, modélisée par une structure topologique d'arrangement 2D. Cette représentation permet des traitements géométriques efficaces et efficients, ainsi qu'une maintenance et une validation aisée au fur et à mesure des éditions lorsque la géométrie ou la topologie d'un objet sont modifiées. A haut niveau, les aspects sémantiques et thématiques des objets géospatiaux sont modélisés et gérés. La hiérarchie entre ces objets est maintenue à travers un graphe dirigé acyclique dans lequel les feuilles correspondent à des primitives géométriques de l'arrangement 2D et les noeuds de plus haut niveau représentent les objets géospatiaux sémantiques plus ou moins aggrégés. Nous avons intégré le modèle de données proposé dans un framework SIG nommé StreetMaker en complément d'un ensemble d'algorithmes génériques et de capacités SIG basiques. Ce framework est alors assez riche pour générer automatiquement des graphes de réseau piétonnier. En effet, dans le cadre d'un projet d'analyse d'accessibilité, le flux de traitement proposé a permis de produire avec succès sur deux sites un graphe de réseau piétonnier à partir de données en entrées variées : des cartes vectorielles existantes, des données vectorielles créées semi-automatiquement et des objets vectoriels extraits d'un nuage de points lidar issu d'une acquisition de cartographie mobile.Alors que la modélisation 2D de la surface du sol est suffisante pour les applications SIG 2D, les applications SIG 3D nécessitent des modèles 3D de l'environnement. La modélisation 3D est un sujet très large mais, dans un premier pas vers cette modélisation 3D, nous nous sommes concentrés sur la modélisation semi-automatique d'objets de type cylindre généralisé (tels que les poteaux, les lampadaires, les troncs d'arbre, etc) à partir d'une seule image. Les méthodes et techniques développées sont présentées et discutée

Poligonal sadeleştirme algoritmalarının karşılaştırılması.

Polygonal meshes are a common way of representing 3D surface models in many different areas of computer graphics and geometry processing. However, these models are becoming more and more complex which increases the cost of processing these models. In order to reduce this cost, mesh simplification algorithms are developed. Another important property of a polygonal mesh model is that whether it is regular or not. Regular meshes have many advantages over the irregular ones in terms of memory requirements, efficient processing, rendering etc. In this thesis work, both mesh simplification and regular remeshing algorithms are studied. Moreover, some of the popular mesh libraries are compared with respect to their approaches and performance to the mesh simplification. In addition, mesh models with disk topology are remeshed and converted to regular ones.M.S. - Master of Scienc

2D Arrangements for Public Space Mapping and Transportation

Cette thèse porte sur le développement facilité d'applications de cartographie et de transport, plus particulièrement sur la génération de réseaux piétonniers pour des applications telles que la navigation, le calcul d'itinéraires, l'analyse d'accessibilité et l'urbanisme. Afin d'atteindre ce but, nous proposons un modèle de données à deux couches qui cartographie l'espace public dans une hiérarchie d'objets géospatiaux sémantisés. A bas niveau, la géométrie 2D des objets géospatiaux est représentée par une partition planaire, modélisée par une structure topologique d'arrangement 2D. Cette représentation permet des traitements géométriques efficaces et efficients, ainsi qu'une maintenance et une validation aisée au fur et à mesure des éditions lorsque la géométrie ou la topologie d'un objet sont modifiées. A haut niveau, les aspects sémantiques et thématiques des objets géospatiaux sont modélisés et gérés. La hiérarchie entre ces objets est maintenue à travers un graphe dirigé acyclique dans lequel les feuilles correspondent à des primitives géométriques de l'arrangement 2D et les noeuds de plus haut niveau représentent les objets géospatiaux sémantiques plus ou moins aggrégés. Nous avons intégré le modèle de données proposé dans un framework SIG nommé StreetMaker en complément d'un ensemble d'algorithmes génériques et de capacités SIG basiques. Ce framework est alors assez riche pour générer automatiquement des graphes de réseau piétonnier. En effet, dans le cadre d'un projet d'analyse d'accessibilité, le flux de traitement proposé a permis de produire avec succès sur deux sites un graphe de réseau piétonnier à partir de données en entrées variées : des cartes vectorielles existantes, des données vectorielles créées semi-automatiquement et des objets vectoriels extraits d'un nuage de points lidar issu d'une acquisition de cartographie mobile.Alors que la modélisation 2D de la surface du sol est suffisante pour les applications SIG 2D, les applications SIG 3D nécessitent des modèles 3D de l'environnement. La modélisation 3D est un sujet très large mais, dans un premier pas vers cette modélisation 3D, nous nous sommes concentrés sur la modélisation semi-automatique d'objets de type cylindre généralisé (tels que les poteaux, les lampadaires, les troncs d'arbre, etc) à partir d'une seule image. Les méthodes et techniques développées sont présentées et discutéesThis thesis addresses easy and effective development of mapping and transportation applications which especially focuses on the generation of pedestrian networks for applications like navigation, itinerary calculation, accessibility analysis and urban planning. In order to achieve this goal, we proposed a two layered data model which encodes the public space into a hierarchy of semantic geospatial objects. At the lower level, the 2D geometry of the geospatial objects are captured using a planar partition which is represented as a topological 2D arrangement. This representation of a planar partition allows efficient and effective geometry processing and easy maintenance and validation throughout the editions when the geometry or topology of an object is modified. At the upper layer, the semantic and thematic aspects of geospatial objects are modelled and managed. The hierarchy between these objects is maintained using a directed acyclic graph (DAG) in which the leaf nodes correspond to the geometric primitives of the 2D arrangement and the higher level nodes represent the aggregated semantic geospatial objects at different levels. We integrated the proposed data model into our GIS framework called StreetMaker together with a set of generic algorithms and basic GIS capabilities. This framework is then rich enough to generate pedestrian network graphs automatically. In fact, within an accessibility analysis project, the full proposed pipeline was successfully used on two sites to produce pedestrian network graphs from various types of input data: existing GIS vector maps, semi-automatically created vector data and vector objects extracted from Mobile Mapping lidar point clouds.While modelling 2D ground surfaces may be sufficient for 2D GIS applications, 3D GIS applications require 3D models of the environment. 3D modelling is a very broad topic but as a first step to such 3D models, we focused on the semi-automatic modelling of objects which can be modelled or approximated by generalized cylinders (such as poles, lampposts, tree trunks, etc.) from single images. The developed methods and techniques are presented and discusse

Regular Remeshing of 3D Human Face Models

Three dimesional polygonal models can be classified into three groups as irregular, semi-regular and regular. Regular models have advantages over the semi-regular and irregular ones in terms of efficient processing, memory requirements and rendering. Although most of the polygonal mesh generating methods yield irregular models, these models can be remeshed regularly. fit this paper, regular remeshing of three dimensional human face models are studied. These models are commonly used in computer graphics and pattern recongnition

Provably Consistent Distributed Delaunay Triangulation

International audienceThis paper deals with the distributed computation of Delaunay triangulations of massive point sets, mainly motivated by the needs of a scalable out-of-core surface reconstruction workflow from massive urban LIDAR datasets. Such a data often corresponds to a huge point cloud represented through a set of tiles of relatively homogeneous point sizes. This will be the input of our algorithm which will naturally partition this data across multiple processing elements. The distributed computation and communication between processing elements is orchestrated efficiently through an uncentralized model to represent, manage and locally construct the triangulation corresponding to each tile. Initially inspired by the star splaying approach, we review the Tile\& Merge algorithm for computing Distributed Delaunay Triangulations on the cloud, provide a theoretical proof of correctness of this algorithm, and analyse the performance of our Spark implementation in terms of speedup and strong scaling in both synthetic and real use case datasets. A HPC implementation (e.g. using MPI), left for future work, would benefit from its more efficient message passing paradigm but lose the robustness and failure resilience of our Spark approach

Tile & Merge: Distributed Delaunay Triangulations for Cloud Computing

International audienceMotivated by the needs of a scalable out-of-core surface reconstruction algorithm available on the cloud, this paper addresses the computation of distributed Delaunay triangulations of massive point sets. The proposed algorithm takes as input a point cloud and first partitions it across multiple processing elements into tiles of relatively homogeneous point sizes. The distributed computation and communication between processing elements is orchestrated so that each one discovers the Delaunay neighbors of its input points within the theoretical overall Delau-nay triangulation of all points and computes locally a partial view of this triangulation. This approach prevents memory limitations by never materializing the global triangulation. This efficiency is due to our proposed uncentralized model to represent, manage and locally construct the triangulation corresponding to each tile. The point set is first partitioned into non-overlapping tiles, then we construct within each tile the Delaunay triangulation of the local points and a minimal set of replicated foreign points in order to capture the simplices spanning multiple tiles. Inspired by the star splaying approach for Delaunay triangulation computation/repair, communication is limited to exchanging points of potential Delaunay neighbors across tiles. Therefore, our method is guaranteed to reconstruct, within each tile, a triangulation that contains the star of its local points, as though it were computed within the Delaunay triangulation of all points. The proposed algorithm is implemented with Spark for the scheduling and C ++ for the geometric computations. This allows both an optimal scheduling on multiple machines and efficient low-level computation. The results show the efficiency of our algorithm in terms of speedup and strong scaling on a classical Spark configuration with both synthetic and real use case datasets

An Examination of the Relationships between Psychological Resilience, Organizational Ostracism, and Burnout in K–12 Teachers through Structural Equation Modelling

Psychological resilience, burnout, and ostracism are significant variables that may affect teachers’ performance and well-being. While psychological resilience is the ability of individuals to cope with the challenges of life/work and could support teachers in performing their profession, burnout (i.e., high levels of emotional exhaustion and desensitization) and ostracism (i.e., being ignored by others in the workplace) could lead to serious negative outcomes for both teachers and the educational system. Despite their significance, studies addressing the relationships between these variables are rare. Therefore, this study aimed to investigate the relationships between teachers’ psychological resilience, burnout, and organizational ostracism. The study used structural equation modeling (SEM) to test the hypothetical relationships between these variables. The participants were selected using a simple random sampling method among K–12 teachers working in Elazig, Turkey. The data were collected using Psychological Resilience Scale—Short Form, Organizational Ostracism Scale, and Burnout Syndrome Inventory—Short Form. Data obtained from 309 K–12 teachers were analyzed using path analysis. The findings showed that teachers’ psychological resilience was quite low, whilst they experienced high levels of burnout and organizational ostracism. The results also showed a negative relationship between their psychological resilience and organizational ostracism and burnout while determining a positive relationship between ostracism and burnout. Psychological resilience was determined to have a moderating role in the relationship between organizational ostracism and burnout. Implications were suggested for both research and practice

Assessment of the Relationships between Prospective Mathematics Teachers’ Classroom Management Anxiety, Academic Self-Efficacy Beliefs, Academic Amotivation and Attitudes toward the Teaching Profession Using Structural Equation Modelling

Academic self-efficacy, academic amotivation, attitude toward the teaching profession, and classroom management anxiety are four of the most significant factors for both teacher training and performance because these psychological and behavioral constructs are first developed during the initial training, and reflect on the actual teaching quality of teachers. Therefore, investigation into their development and relationships, particularly with regard to prospective teachers, is significant both for the theory and practice of teaching. Hence, the current study aims to explore the casual relationships between these variables with a sample of prospective mathematics teachers, using the structural equation modelling (SEM). The participants were selected using simple random sampling method from prospective mathematics teachers studying at educational faculties of seven universities in different regions of Turkey. The data were collected using the academic amotivation scale, academic self-efficacy scale, attitude toward the teaching profession scale, classroom management anxiety scale, and a personal information form developed by the researchers. Data obtained from 581 participants were analyzed using path analysis. The findings showed that prospective mathematics teachers had a positive attitude toward the profession, and were eager to teach. Their academic self-efficacy predicted their attitude toward the teaching profession. Similarly, prospective mathematics teachers’ attitude toward the teaching profession correlated negatively with their academic amotivation. In other words, as prospective mathematics teachers’ attitude scores toward the profession increased, their academic amotivation scores decreased. However, prospective mathematics teachers had a high level of classroom management anxiety. Interestingly, prospective mathematics teachers with a positive attitude toward the profession experienced higher levels of classroom management anxiety. The findings mostly supported previous results in the literature. Implications were suggested both for teacher training and practice of quality teaching