Modeling of natural phenomena has been of particular interest in the graphics ommunity in recent years. This thesis will explore a method for creating and animating orb webs using a coupled spring-mass system. Using a spring-mass system for creating the orb web is ideal as we can represent each web strand using coupled spring-mass pairs. This allows the orb web simulator to be physically based, i.e., the simulation follows the laws that act on objects in the real world. This in turn simplifies the process of animating the web, as the animation emerges from the simulator without anyone having to set it up explicitly. Since this model is physically based, it would allow for realistic visualization of effects such as observing an orb web under a wind. In the children's book ``Charlotte's Web', the spider creates orb webs with words inscribed on them. Charlotte's web is used as an inspiration, in this thesis, to create webs which no real world spider could possibly create, while keeping the model physically based. This involves modifying the orb web such that the target text shows up on the orb web while keeping the web looking as natural as possible.

This thesis describes two new techniques for enhancing the rendering quality of cartoon characters in toon-shading applications. The proposed methods can be used to improve the output quality of current cel shaders. The first technique which uses 2D image-based algorithms, enhances the silhouettes of the input geometry and reduces the computer generated artefacts. The silhouettes are found by using the Sobel filter and reconstructed by Bezier curve fitting. The intensity of the reconstructed silhouettes is then modified to create a stylised appearance. In the second technique, a new hair model based on billboarded particles is introduced. This method is found to be particularly useful for generating toon-like specular highlights for hair, which are important in cartoon animations. The whole rendering framework is implemented in C++ using the OpenGL API. OpenGL extensions and GPU programming are used to take the advantage of the functionalities of currently available graphics hardware. The programming of graphics hardware is done using Cg, a high level shader language.

Pixel art is a popular style of digital art often found in video games. It is typically characterized by its low resolution and use of limited colour palettes. Pixel art is created manually with little automation because it requires attention to pixel-level details. Working with individual pixels is a challenging and abstract task, whereas manipulating higher-level objects in vector graphics is much more intuitive. However, it is difficult to bridge this gap because although many rasterization algorithms exist, they are not well-suited for the particular needs of pixel artists, particularly at low resolutions. In this thesis, we introduce a class of rasterization algorithms called pixelation that is tailored to pixel art needs. We describe how our algorithm suppresses artifacts when pixelating vector paths and preserves shape-level features when pixelating geometric primitives. We also developed methods inspired by pixel art for drawing lines and angles more effectively at low resolutions. We compared our results to rasterization algorithms, rasterizers used in commercial software, and human subjects---both amateurs and pixel artists. Through formal analyses of our user study studies and a close collaboration with professional pixel artists, we showed that, in general, our pixelation algorithms produce more visually appealing results than na\"{i}ve rasterization algorithms do.

Although proprietary and free web map applications have become an important part of daily life, individual map styling has been neglected for a fairly long time. With the latest possibilities of custom adjustment provided by many services and some interesting artistic experiments, this is about to change. In the context of artistic cartography and custom map styling, this work explores the possibilities of employing an automated process for the generation of WMTS compatible map tiles with an artistic styling. Web mapping standards and techniques of non-photorealistic rendering (NPR) are considered as well as traditional cartographic representations. Furthermore, existing vector- and raster-based processes are analyzed including an interactive workflow with the open-source image editing software GIMP, which is examined with respect to its drawing capabilities. Based on this, a concept for an automated rendering process is developed and influencing factors along with input parameters are discussed. An experimental automated processing is implemented using GIMP and its Python scripting interface to create single maps and seamless map tiles for the use in a WMTS application. Different drawing techniques of GIMP, such as brushes, dynamics and masks are applied during the rendering process. Geodata is taken from the freely available OpenStreetMap project and it is stored in a geodatabase. Furthermore, the GIS capabilities of the database are used to implement custom query procedures for the creation of seamless tiles, feature simplification and generalization that makes a preprocessing of the data unnecessary. Additionally randomization methods for the estrangement and abstraction of the SVG vector graphics geometry to emulate a hand-drawn appearance are created based on non-photorealistic rendering techniques. As a result, various rendering and abstraction processes are evaluated and discussed regarding their contribution to an artistic appearance. Map tiles are created using these stylings which are WMTS compatible and can be presented in a web mapping application.

Although proprietary and free web map applications have become an important part of daily life, individual map styling has been neglected for a fairly long time. With the latest possibilities of custom adjustment provided by many services and some interesting artistic experiments, this is about to change. In the context of artistic cartography and custom map styling, this work explores the possibilities of employing an automated process for the generation of WMTS compatible map tiles with an artistic styling. Web mapping standards and techniques of non-photorealistic rendering (NPR) are considered as well as traditional cartographic representations. Furthermore, existing vector- and raster-based processes are analyzed including an interactive workflow with the open-source image editing software GIMP, which is examined with respect to its drawing capabilities. Based on this, a concept for an automated rendering process is developed and influencing factors along with input parameters are discussed. An experimental automated processing is implemented using GIMP and its Python scripting interface to create single maps and seamless map tiles for the use in a WMTS application. Different drawing techniques of GIMP, such as brushes, dynamics and masks are applied during the rendering process. Geodata is taken from the freely available OpenStreetMap project and it is stored in a geodatabase. Furthermore, the GIS capabilities of the database are used to implement custom query procedures for the creation of seamless tiles, feature simplification and generalization that makes a preprocessing of the data unnecessary. Additionally randomization methods for the estrangement and abstraction of the SVG vector graphics geometry to emulate a hand-drawn appearance are created based on non-photorealistic rendering techniques. As a result, various rendering and abstraction processes are evaluated and discussed regarding their contribution to an artistic appearance. Map tiles are created using these stylings which are WMTS compatible and can be presented in a web mapping application.:Contents Task Description III Abstract V Declaration of authorship VII Acknowledgements IX Table of Contents XIII List of Figures XVI List of Tables XVIII Glossary XX 1 Introduction1 1.1 Motivation 1 1.2 Objectives 1 1.3 Structure of the work 2 2 Cartographic context and NPR 5 2.1 Definitions 5 2.2 Non-photorealistic rendering 7 2.2.1 NPR in computer graphics 7 2.2.2 Hand-drawn rendering 10 2.3 Cartographic communication and visualization 12 2.4 Cartography and art 14 2.5 Web Mapping 17 3 Image editing and web map rendering 19 3.1 Image editing software 19 3.2 Raster image editing with GIMP 20 3.2.1 Interactive editing 20 3.2.2 Plug-ins and scripting 28 3.3 Map rendering 31 3.3.1 Web map rendering techniques 31 3.3.2 Comparison of vector and raster based approaches 33 3.3.3 An interactive workflow with GIMP 36 4 A concept for automated processing 39 4.1 Comparison of influencing factors of a vector and raster based approach 39 4.2 Requirements and goals of automation 41 4.3 Definition of input parameters 43 4.4 Concept for an automated process with GIMP 43 4.5 Technical components 45 4.5.1 JSON 45 4.5.2 OpenStreetMap 46 4.5.3 Database environment 47 4.5.4 SVG as exchange format 47 4.5.5 Web map tile service 49 5 Implementation of an automated process with GIMP 53 5.1 Geodata setup 53 5.1.1 Data acquisition 53 5.1.2 Data import and update 54 5.2 Sketch rendering 56 5.2.1 Displacement and randomization 57 5.2.2 Hand-drawn emulation 60 5.2.3 Hatching 64 5.3 Automated processing 65 5.3.1 Configuration files 66 5.3.2 Script structure 70 5.3.3 Feature Processing 74 5.3.4 Image rendering 78 5.3.5 Output and WMTS 80 6 Processing results and evaluation 83 6.1 Results 83 6.2 Limitations and potential 87 7 Conclusion 93 7.1 Summary 93 7.2 Outlook 94

Die Verwendung von ikonographischen, bildhaften Kartenzeichen ist sehr beliebt bei der Darstellung von Sehenswürdigkeiten in touristischen Karten sowie bei Kartendarstellungen für Kinder und Jugendliche. Der Begriff des Non-Photorealistic Rendering (NPR) beschreibt einen zentralen Bereich in der Computergrafik, der sich mit der Erzeugung von Bildern auseinandersetzt, die scheinbar handgemacht sind und bewusst nicht dem physikalisch korrekten Abbild eines Modells entsprechen. Ein weiteres Trendthema zur Nachahmung eines bestimmten Stils eines Kunstwerks stellt der Neural Style Transfer (NST) dar. Hierbei werden künstlerische Bilder durch Trennung und Rekombination von Bildinhalt und Stil erzeugt. Im Rahmen der vorliegenden Arbeit ist ein semi-automatischer Workflow zur Erzeugung ikonographischer Gebäudedarstellungen für die Nutzung in zoombaren Webkarten entwickelt und in drei künstlerischen Stilvarianten unter Nutzung von Bildverarbeitungswerkzeugen in dem rasterbasierten Open Source Bildbearbeitungsprogramm GIMP, speziell mit der Filtersammlung G'MIC technisch umgesetzt worden. Außerdem zeigt die Masterarbeit das Potential der Ableitung von ikonographischen Signaturen durch den Style-Transfer mittels neuronaler Netze.:Selbstständigkeitserklärung III Inhaltsverzeichnis 5 Abbildungsverzeichnis 7 Tabellenverzeichnis 8 Abkürzungsverzeichnis 9 1 Einleitung 10 1.1 Motivation 10 1.2 Gliederung der Arbeit 10 2 Literaturstudium 11 2.1 Computergrafik 11 2.2 Non-Photorealistic Rendering 11 2.3 Neural Style Transfer 14 2.3.1 Einleitung 14 2.3.2 Convolutional Neural Network 15 2.3.3 Beschreibung des Algorithmus 17 3 Methodik 19 3.1 Technische Komponenten 19 3.2 Kriterien der Bildauswahl 19 3.3 Workflow „Ölmalerei“ 21 3.4 Workflow „Tuschezeichnung 22 3.5 Workflow „Silhouette“ 22 4 Praktischer Teil 23 4.1 Konkrete Umsetzung 23 4.1.1 Workflow „Ölmalerei“ 24 4.1.2 Workflow „Tuschezeichnung“ 32 4.1.3 Workflow „Silhouette“ 32 4.2 Implementierung eines Automatisierungsprozesses 35 4.3 Anwendung: Karte Dresden 39 4.4 Neural Style Transfer 43 4.4.1 Online-Anwendungen 43 4.4.2 Offline-Implementierung 45 5 Diskussion 51 5.1 Resultate 51 5.1.1 Bildverarbeitung 51 5.1.2 Neural Style Transfer 51 5.2 Ausblick 52 6 Zusammenfassung 52 Literaturverzeichnis 53 / The use of iconographic, pictorial map symbols is very popular for the representation of places of interest in tourist maps as well as for map presentations for children and young people. The term Non-Photorealistic Rendering (NPR) describes a prominent field in computer graphics that deals with the generation of images that are apparently handmade and deliberately do not correspond to the physically correct image of a model. Neural Style Transfer (NST) is another trend topic for imitating a certain style of an artwork. Here, artistic images are created by separating and recombining image content and style. In the context of the present work, a semi-automatic workflow for the creation of iconographic building representations for use in zoomable web maps has been developed and technically implemented in three artistic style variants using image processing tools in the raster-based open source image processing program GIMP, especially with the filter collection G'MIC. In addition, the master thesis demonstrates the potential of deriving iconographic signatures through style transfer using neural networks.:Selbstständigkeitserklärung III Inhaltsverzeichnis 5 Abbildungsverzeichnis 7 Tabellenverzeichnis 8 Abkürzungsverzeichnis 9 1 Einleitung 10 1.1 Motivation 10 1.2 Gliederung der Arbeit 10 2 Literaturstudium 11 2.1 Computergrafik 11 2.2 Non-Photorealistic Rendering 11 2.3 Neural Style Transfer 14 2.3.1 Einleitung 14 2.3.2 Convolutional Neural Network 15 2.3.3 Beschreibung des Algorithmus 17 3 Methodik 19 3.1 Technische Komponenten 19 3.2 Kriterien der Bildauswahl 19 3.3 Workflow „Ölmalerei“ 21 3.4 Workflow „Tuschezeichnung 22 3.5 Workflow „Silhouette“ 22 4 Praktischer Teil 23 4.1 Konkrete Umsetzung 23 4.1.1 Workflow „Ölmalerei“ 24 4.1.2 Workflow „Tuschezeichnung“ 32 4.1.3 Workflow „Silhouette“ 32 4.2 Implementierung eines Automatisierungsprozesses 35 4.3 Anwendung: Karte Dresden 39 4.4 Neural Style Transfer 43 4.4.1 Online-Anwendungen 43 4.4.2 Offline-Implementierung 45 5 Diskussion 51 5.1 Resultate 51 5.1.1 Bildverarbeitung 51 5.1.2 Neural Style Transfer 51 5.2 Ausblick 52 6 Zusammenfassung 52 Literaturverzeichnis 53

Image based lighting, (IBL), is a computer graphics technique for creating photorealistic renderings of synthetic objects such that they can be placed into real world scenes. IBL has been widely recognized and is today used in commercial production pipelines. However, the current techniques only use illumination captured at a single point in space. This means that traditional IBL cannot capture or recreate effects such as cast shadows, shafts of light or other important spatial variations in the illumination. Such lighting effects are, in many cases, artistically created or are there to emphasize certain features, and are therefore a very important part of the visual appearance of a scene. This thesis and the included papers present methods that extend IBL to allow for capture and rendering with spatially varying illumination. This is accomplished by measuring the light field incident onto a region in space, called an Incident Light Field, (ILF), and using it as illumination in renderings. This requires the illumination to be captured at a large number of points in space instead of just one. The complexity of the capture methods and rendering algorithms are then significantly increased. The technique for measuring spatially varying illumination in real scenes is based on capture of High Dynamic Range, (HDR), image sequences. For efficient measurement, the image capture is performed at video frame rates. The captured illumination information in the image sequences is processed such that it can be used in computer graphics rendering. By extracting high intensity regions from the captured data and representing them separately, this thesis also describes a technique for increasing rendering efficiency and methods for editing the captured illumination, for example artificially moving or turning on and of individual light sources.

<p>The aim with this thesis is to develop a plugin; Lovefish, for the purpose of allowing non-realistic renderings (NPR) for visualisation in Newtek Lightwave3D. The main purpose with Lovefish is to offer textured tones, something that has not been offered before by any previously existing shader for Lightwav3D. The textured tones are a substantially widening of what is possible to imitate in the field of classical art techniques. Among others has a number of SIGGRAPH papers has been the foundation and a source of inspiration for what has been achieve in this project. Further has this thesis treated a number of questions: what is non-photorealistic rendering is and how it works; an overview of the Lightwave3Ds software development kit (SDK).</p>

The aim with this thesis is to develop a plugin; Lovefish, for the purpose of allowing non-realistic renderings (NPR) for visualisation in Newtek Lightwave3D. The main purpose with Lovefish is to offer textured tones, something that has not been offered before by any previously existing shader for Lightwav3D. The textured tones are a substantially widening of what is possible to imitate in the field of classical art techniques. Among others has a number of SIGGRAPH papers has been the foundation and a source of inspiration for what has been achieve in this project. Further has this thesis treated a number of questions: what is non-photorealistic rendering is and how it works; an overview of the Lightwave3Ds software development kit (SDK).

Research and development of Non-Photorealistic Rendering algorithms has recently moved towards the use of computer vision algorithms to extract image features. The feature representation capabilities of image moments could be used effectively for the selection of brush-stroke characteristics for painterly-rendering applications. This technique is based on the estimation of local geometric features from the intensity distribution in small windowed images to obtain the brush size, color and direction. This thesis proposes an improvement of this method, by additionally extracting the connected components so that the adjacent regions of similar color are grouped for generating large and noticeable brush-stroke images. An iterative coarse-to-fine rendering algorithm is developed for painting regions of varying color frequencies. Improvements over the existing technique are discussed with several examples.