TY - JOUR A1 - Richter, Rico A1 - Kyprianidis, Jan Eric A1 - Döllner, Jürgen Roland Friedrich T1 - Out-of-core GPU-based change detection in massive 3D point clouds JF - Transactions in GIS N2 - If sites, cities, and landscapes are captured at different points in time using technology such as LiDAR, large collections of 3D point clouds result. Their efficient storage, processing, analysis, and presentation constitute a challenging task because of limited computation, memory, and time resources. In this work, we present an approach to detect changes in massive 3D point clouds based on an out-of-core spatial data structure that is designed to store data acquired at different points in time and to efficiently attribute 3D points with distance information. Based on this data structure, we present and evaluate different processing schemes optimized for performing the calculation on the CPU and GPU. In addition, we present a point-based rendering technique adapted for attributed 3D point clouds, to enable effective out-of-core real-time visualization of the computation results. Our approach enables conclusions to be drawn about temporal changes in large highly accurate 3D geodata sets of a captured area at reasonable preprocessing and rendering times. We evaluate our approach with two data sets from different points in time for the urban area of a city, describe its characteristics, and report on applications. Y1 - 2013 U6 - https://doi.org/10.1111/j.1467-9671.2012.01362.x SN - 1361-1682 VL - 17 IS - 5 SP - 724 EP - 741 PB - Wiley-Blackwell CY - Hoboken ER - TY - THES A1 - Kyprianidis, Jan Eric T1 - Structure adaptive stylization of images and video T1 - Strukturadaptive Stilisierung von Bildern und Videos N2 - In the early days of computer graphics, research was mainly driven by the goal to create realistic synthetic imagery. By contrast, non-photorealistic computer graphics, established as its own branch of computer graphics in the early 1990s, is mainly motivated by concepts and principles found in traditional art forms, such as painting, illustration, and graphic design, and it investigates concepts and techniques that abstract from reality using expressive, stylized, or illustrative rendering techniques. This thesis focuses on the artistic stylization of two-dimensional content and presents several novel automatic techniques for the creation of simplified stylistic illustrations from color images, video, and 3D renderings. Primary innovation of these novel techniques is that they utilize the smooth structure tensor as a simple and efficient way to obtain information about the local structure of an image. More specifically, this thesis contributes to knowledge in this field in the following ways. First, a comprehensive review of the structure tensor is provided. In particular, different methods for integrating the minor eigenvector field of the smoothed structure tensor are developed, and the superiority of the smoothed structure tensor over the popular edge tangent flow is demonstrated. Second, separable implementations of the popular bilateral and difference of Gaussians filters that adapt to the local structure are presented. These filters avoid artifacts while being computationally highly efficient. Taken together, both provide an effective way to create a cartoon-style effect. Third, a generalization of the Kuwahara filter is presented that avoids artifacts by adapting the shape, scale, and orientation of the filter to the local structure. This causes directional image features to be better preserved and emphasized, resulting in overall sharper edges and a more feature-abiding painterly effect. In addition to the single-scale variant, a multi-scale variant is presented, which is capable of performing a highly aggressive abstraction. Fourth, a technique that builds upon the idea of combining flow-guided smoothing with shock filtering is presented, allowing for an aggressive exaggeration and an emphasis of directional image features. All presented techniques are suitable for temporally coherent per-frame filtering of video or dynamic 3D renderings, without requiring expensive extra processing, such as optical flow. Moreover, they can be efficiently implemented to process content in real-time on a GPU. N2 - In den Anfängen der Computergrafik war die Forschung hauptsächlich von dem Anspruch getragen, realistisch aussehende synthetische Bilder zu erstellen. Im Gegensatz dazu ist die nicht-photorealistische Computergraphik, ein Untergebiet der Computergrafik, welches in den frühen 1990er Jahren gegründet wurde, vor allem motiviert durch Konzepte und Prinzipien der traditionellen Kunst wie Malerei, Illustration und Grafikdesign. Diese Arbeit beschäftigt sich mit der künstlerischen Verarbeitung von zweidimensionalen Bildinhalten und präsentiert mehrere neue automatische Verfahren für die Erstellung von vereinfachten künstlerischen Darstellungen von Farbbildern, Videos und 3D- Renderings. Wichtigste Neuerung dieser Techniken ist die Verwendung des Strukturtensors als eine einfache und effiziente Möglichkeit, Informationen über die lokale Struktur eines Bildes zu erhalten. Konkret werden die folgenden Beiträge gemacht. Erstens wird eine umfassende übersicht über den Strukturtensor gegeben. Insbesondere werden verschiedene Methoden für die Integration des kleineren Eigenvektorfeldes des geglätteten Strukturtensors entwickelt, und die Überlegenheit des geglätteten Strukturtensors gegenüber dem populären Edge-Tangent-Flow demonstriert. Zweitens werden separable Implementierungen des bilateralen Filters und des Difference of Gaussians Filters vorgestellt. Durch die Anpassung der Filter an die lokale Struktur des Bildes werden Bildfehler vermieden, wobei der Vorgang rechnerisch effizient bleibt. Zusammengenommen bieten beide Techniken eine effektive Möglichkeit, um einen Cartoon-ähnlichen Effekt zu erzielen. Drittens wird eine Verallgemeinerung des Kuwahara-Filters vorgestellt. Durch die Anpassung von Form, Umfang und Orientierung der Filter an die lokale Struktur werden Bildfehler verhindert. Außerdem werden direktionale Bildmerkmale besser berücksichtigt und betont, was zu schärferen Kanten und einem malerischen Effekt führt. Neben der single-scale Variante wird auch eine multi-scale Variante vorgestellt, welche im Stande ist, eine höhere Abstraktion zu erzielen. Viertens wird eine Technik vorgestellt, die auf der Kombination von flussgesteuerter Glättung und Schock-Filterung beruht, was zu einer intensiven Verstärkung und Betonung der direktionalen Bildmerkmale führt. Alle vorgestellten Techniken erlauben die zeitlich kohärente Verarbeitung von Einzelbildern eines Videos oder einer dynamischen 3D-Szene, ohne dass andere aufwendige Verfahren wie zum Beispiel die Berechnung des optischen Flusses, benötigt werden. Darüberhinaus können die Techniken effizient implementiert werden und ermöglichen die Verarbeitung in Echtzeit auf einem Grafikprozessor (GPU). KW - Nicht-photorealistisches Rendering KW - Flussgesteuerter Bilateraler Filter KW - Differenz von Gauss Filtern KW - Anisotroper Kuwahara Filter KW - non-photorealistic rendering KW - flow-based bilateral filter KW - difference of Gaussians KW - anisotropic Kuwahara filter KW - coherence-enhancing filtering Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-64104 ER - TY - JOUR A1 - Kyprianidis, Jan Eric A1 - Collomosse, John A1 - Wang, Tinghuai A1 - Isenberg, Tobias T1 - State of the "Art" a taxonomy of artistic stylization techniques for images and video JF - IEEE transactions on visualization and computer graphics N2 - This paper surveys the field of nonphotorealistic rendering (NPR), focusing on techniques for transforming 2D input (images and video) into artistically stylized renderings. We first present a taxonomy of the 2D NPR algorithms developed over the past two decades, structured according to the design characteristics and behavior of each technique. We then describe a chronology of development from the semiautomatic paint systems of the early nineties, through to the automated painterly rendering systems of the late nineties driven by image gradient analysis. Two complementary trends in the NPR literature are then addressed, with reference to our taxonomy. First, the fusion of higher level computer vision and NPR, illustrating the trends toward scene analysis to drive artistic abstraction and diversity of style. Second, the evolution of local processing approaches toward edge-aware filtering for real-time stylization of images and video. The survey then concludes with a discussion of open challenges for 2D NPR identified in recent NPR symposia, including topics such as user and aesthetic evaluation. KW - Image and video stylization KW - nonphotorealistic rendering (NPR) KW - artistic rendering Y1 - 2013 U6 - https://doi.org/10.1109/TVCG.2012.160 SN - 1077-2626 VL - 19 IS - 5 SP - 866 EP - 885 PB - Inst. of Electr. and Electronics Engineers CY - Los Alamitos ER -