An Investigation into Animating Plant Structures within Real-time Constraints

This paper is an analysis of current developments in rendering botanical structures for scientic and entertainment purposes with a focus on visualising growth. The choices of practical investigations produce a novel approach for parallel parsing of difficult bracketed L-Systems, based upon the work of Lipp, Wonka and Wimmer (2010). Alongside this is a general overview of the issues involved when looking at growing systems, technical details involving programming for the Graphics Processing Unit (GPU) and other possible solutions for further work that also could achieve the project's goals

Towards Predictive Rendering in Virtual Reality

The strive for generating predictive images, i.e., images representing radiometrically correct renditions of reality, has been a longstanding problem in computer graphics. The exactness of such images is extremely important for Virtual Reality applications like Virtual Prototyping, where users need to make decisions impacting large investments based on the simulated images. Unfortunately, generation of predictive imagery is still an unsolved problem due to manifold reasons, especially if real-time restrictions apply. First, existing scenes used for rendering are not modeled accurately enough to create predictive images. Second, even with huge computational efforts existing rendering algorithms are not able to produce radiometrically correct images. Third, current display devices need to convert rendered images into some low-dimensional color space, which prohibits display of radiometrically correct images. Overcoming these limitations is the focus of current state-of-the-art research. This thesis also contributes to this task. First, it briefly introduces the necessary background and identifies the steps required for real-time predictive image generation. Then, existing techniques targeting these steps are presented and their limitations are pointed out. To solve some of the remaining problems, novel techniques are proposed. They cover various steps in the predictive image generation process, ranging from accurate scene modeling over efficient data representation to high-quality, real-time rendering. A special focus of this thesis lays on real-time generation of predictive images using bidirectional texture functions (BTFs), i.e., very accurate representations for spatially varying surface materials. The techniques proposed by this thesis enable efficient handling of BTFs by compressing the huge amount of data contained in this material representation, applying them to geometric surfaces using texture and BTF synthesis techniques, and rendering BTF covered objects in real-time. Further approaches proposed in this thesis target inclusion of real-time global illumination effects or more efficient rendering using novel level-of-detail representations for geometric objects. Finally, this thesis assesses the rendering quality achievable with BTF materials, indicating a significant increase in realism but also confirming the remainder of problems to be solved to achieve truly predictive image generation

Physical Adversarial Examples for Multi-Camera Systems

Neural networks build the foundation of several intelligent systems, which, however, are known to be easily fooled by adversarial examples. Recent advances made these attacks possible even in air-gapped scenarios, where the autonomous system observes its surroundings by, e.g., a camera. We extend these ideas in our research and evaluate the robustness of multi-camera setups against such physical adversarial examples. This scenario becomes ever more important with the rise in popularity of autonomous vehicles, which fuse the information of several cameras for their driving decision. While we find that multi-camera setups provide some robustness towards past attack methods, we see that this advantage reduces when optimizing on multiple perspectives at once. We propose a novel attack method that we call Transcender-MC, where we incorporate online 3D renderings and perspective projections in the training process. Moreover, we motivate that certain data augmentation techniques can facilitate the generation of successful adversarial examples even further. Transcender-MC is 11% more effective in successfully attacking multi-camera setups than state-of-the-art methods. Our findings offer valuable insights regarding the resilience of object detection in a setup with multiple cameras and motivate the need of developing adequate defense mechanisms against them

Volumetric Reconstruction and Interactive Rendering of Trees from Photographs

International audienceReconstructing and rendering trees is a challenging problem due to the geometric complexity involved, and the inherent difficulties of capture. In this paper we propose a volumetric approach to capture and render trees with relatively sparse foliage. Photographs of such trees typically have single pixels containing the blended projection of numerous leaves/branches and background. We show how we estimate opacity values on a recursive grid, based on alphamattes extracted from a small number of calibrated photographs of a tree. This data structure is then used to render billboards attached to the centers of the grid cells. Each billboard is assigned a set of view-dependent textures corresponding to each input view. These textures are generated by approximating coverage masks based on opacity and depth from the camera. Rendering is performed using a view-dependent texturing algorithm. The resulting volumetric tree structure has low polygon count, permitting interactive rendering of realistic 3D trees. We illustrate the implementation of our system on several different real trees, and show that we can insert the resulting model in virtual scenes

07171 Abstracts Collection -- Visual Computing -- Convergence of Computer Graphics and Computer Vision

From 22.04. to 27.04.2007, the Dagstuhl Seminar 07171 ``Visual Computing - Convergence of Computer Graphics and Computer Vision\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

Interactive mixed reality rendering in a distributed ray tracing framework

The recent availability of interactive ray tracing opened the way for new applications and for improving existing ones in terms of quality. Since today CPUs are still too slow for this purpose, the necessary computing power is obtained by connecting a number of machines and using distributed algorithms. Mixed reality rendering - the realm of convincingly combining real and virtual parts to a new composite scene - needs a powerful rendering method to obtain a photorealistic result. The ray tracing algorithm thus provides an excellent basis for photorealistic rendering and also advantages over other methods. It is worth to explore its abilities for interactive mixed reality rendering. This thesis shows the applicability of interactive ray tracing for mixed (MR) and augmented reality (AR) applications on the basis of the OpenRT framework. Two extensions to the OpenRT system are introduced and serve as basic building blocks: streaming video textures and in-shader AR view compositing. Streaming video textures allow for inclusion of the real world into interactive applications in terms of imagery. The AR view compositing mechanism is needed to fully exploit the advantages of modular shading in a ray tracer. A number of example applications from the entire spectrum of the Milgram Reality-Virtuality continuum illustrate the practical implications. An implementation of a classic AR scenario, inserting a virtual object into live video, shows how a differential rendering method can be used in combination with a custom build real-time lightprobe device to capture the incident light and include it into the rendering process to achieve convincing shading and shadows. Another field of mixed reality rendering is the insertion of real actors into a virtual scene in real-time. Two methods - video billboards and a live 3D visual hull reconstruction - are discussed. The implementation of live mixed reality systems is based on a number of technologies beside rendering and a comprehensive understanding of related methods and hardware is necessary. Large parts of this thesis hence deal with the discussion of technical implementations and design alternatives. A final summary discusses the benefits and drawbacks of interactive ray tracing for mixed reality rendering.Die Verfügbarkeit von interaktivem Ray-Tracing ebnet den Weg für neue Anwendungen, aber auch für die Verbesserung der Qualität bestehener Methoden. Da die heute verfügbaren CPUs noch zu langsam sind, ist es notwendig, mehrere Maschinen zu verbinden und verteilte Algorithmen zu verwenden. Mixed Reality Rendering - die Technik der überzeugenden Kombination von realen und synthetischen Teilen zu einer neuen Szene - braucht eine leistungsfähige Rendering-Methode um photorealistische Ergebnisse zu erzielen. Der Ray-Tracing-Algorithmus bietet hierfür eine exzellente Basis, aber auch Vorteile gegenüber anderen Methoden. Es ist naheliegend, die Möglichkeiten von Ray-Tracing für Mixed-Reality-Anwendungen zu erforschen. Diese Arbeit zeigt die Anwendbarkeit von interaktivem Ray-Tracing für Mixed-Reality (MR) und Augmented-Reality (AR) Anwendungen anhand des OpenRT-Systems. Zwei Erweiterungen dienen als Grundbausteine: Videotexturen und In-Shader AR View Compositing. Videotexturen erlauben die reale Welt in Form von Bildern in den Rendering-Prozess mit einzubeziehen. Der View-Compositing-Mechanismus is notwendig um die Modularität einen Ray-Tracers voll auszunutzen. Eine Reihe von Beispielanwendungen von beiden Enden des Milgramschen Reality-Virtuality-Kontinuums verdeutlichen die praktischen Aspekte. Eine Implementierung des klassischen AR-Szenarios, das Einfügen eines virtuellen Objektes in eine Live-Übertragung zeigt, wie mittels einer Differential Rendering Methode und einem selbstgebauten Gerät zur Erfassung des einfallenden Lichts realistische Beleuchtung und Schatten erzielt werden können. Ein anderer Anwendungsbereich ist das Einfügen einer realen Person in eine künstliche Szene. Hierzu werden zwei Methoden besprochen: Video-Billboards und eine interaktive 3D Rekonstruktion. Da die Implementierung von Mixed-Reality-Anwendungen Kentnisse und Verständnis einer ganzen Reihe von Technologien nebem dem eigentlichen Rendering voraus setzt, ist eine Diskussion der technischen Grundlagen ein wesentlicher Bestandteil dieser Arbeit. Dies ist notwenig, um die Entscheidungen für bestimmte Designalternativen zu verstehen. Den Abschluss bildet eine Diskussion der Vor- und Nachteile von interaktivem Ray-Tracing für Mixed Reality Anwendungen

Interactive mixed reality rendering in a distributed ray tracing framework

The recent availability of interactive ray tracing opened the way for new applications and for improving existing ones in terms of quality. Since today CPUs are still too slow for this purpose, the necessary computing power is obtained by connecting a number of machines and using distributed algorithms. Mixed reality rendering - the realm of convincingly combining real and virtual parts to a new composite scene - needs a powerful rendering method to obtain a photorealistic result. The ray tracing algorithm thus provides an excellent basis for photorealistic rendering and also advantages over other methods. It is worth to explore its abilities for interactive mixed reality rendering. This thesis shows the applicability of interactive ray tracing for mixed (MR) and augmented reality (AR) applications on the basis of the OpenRT framework. Two extensions to the OpenRT system are introduced and serve as basic building blocks: streaming video textures and in-shader AR view compositing. Streaming video textures allow for inclusion of the real world into interactive applications in terms of imagery. The AR view compositing mechanism is needed to fully exploit the advantages of modular shading in a ray tracer. A number of example applications from the entire spectrum of the Milgram Reality-Virtuality continuum illustrate the practical implications. An implementation of a classic AR scenario, inserting a virtual object into live video, shows how a differential rendering method can be used in combination with a custom build real-time lightprobe device to capture the incident light and include it into the rendering process to achieve convincing shading and shadows. Another field of mixed reality rendering is the insertion of real actors into a virtual scene in real-time. Two methods - video billboards and a live 3D visual hull reconstruction - are discussed. The implementation of live mixed reality systems is based on a number of technologies beside rendering and a comprehensive understanding of related methods and hardware is necessary. Large parts of this thesis hence deal with the discussion of technical implementations and design alternatives. A final summary discusses the benefits and drawbacks of interactive ray tracing for mixed reality rendering.Die Verfügbarkeit von interaktivem Ray-Tracing ebnet den Weg für neue Anwendungen, aber auch für die Verbesserung der Qualität bestehener Methoden. Da die heute verfügbaren CPUs noch zu langsam sind, ist es notwendig, mehrere Maschinen zu verbinden und verteilte Algorithmen zu verwenden. Mixed Reality Rendering - die Technik der überzeugenden Kombination von realen und synthetischen Teilen zu einer neuen Szene - braucht eine leistungsfähige Rendering-Methode um photorealistische Ergebnisse zu erzielen. Der Ray-Tracing-Algorithmus bietet hierfür eine exzellente Basis, aber auch Vorteile gegenüber anderen Methoden. Es ist naheliegend, die Möglichkeiten von Ray-Tracing für Mixed-Reality-Anwendungen zu erforschen. Diese Arbeit zeigt die Anwendbarkeit von interaktivem Ray-Tracing für Mixed-Reality (MR) und Augmented-Reality (AR) Anwendungen anhand des OpenRT-Systems. Zwei Erweiterungen dienen als Grundbausteine: Videotexturen und In-Shader AR View Compositing. Videotexturen erlauben die reale Welt in Form von Bildern in den Rendering-Prozess mit einzubeziehen. Der View-Compositing-Mechanismus is notwendig um die Modularität einen Ray-Tracers voll auszunutzen. Eine Reihe von Beispielanwendungen von beiden Enden des Milgramschen Reality-Virtuality-Kontinuums verdeutlichen die praktischen Aspekte. Eine Implementierung des klassischen AR-Szenarios, das Einfügen eines virtuellen Objektes in eine Live-Übertragung zeigt, wie mittels einer Differential Rendering Methode und einem selbstgebauten Gerät zur Erfassung des einfallenden Lichts realistische Beleuchtung und Schatten erzielt werden können. Ein anderer Anwendungsbereich ist das Einfügen einer realen Person in eine künstliche Szene. Hierzu werden zwei Methoden besprochen: Video-Billboards und eine interaktive 3D Rekonstruktion. Da die Implementierung von Mixed-Reality-Anwendungen Kentnisse und Verständnis einer ganzen Reihe von Technologien nebem dem eigentlichen Rendering voraus setzt, ist eine Diskussion der technischen Grundlagen ein wesentlicher Bestandteil dieser Arbeit. Dies ist notwenig, um die Entscheidungen für bestimmte Designalternativen zu verstehen. Den Abschluss bildet eine Diskussion der Vor- und Nachteile von interaktivem Ray-Tracing für Mixed Reality Anwendungen

Visualization of Industrial Structures with Implicit GPU Primitives

International audienceWe present a method to interactively visualize large industrial models by replacing most triangles with implicit GPU primitives: cylinders, cone and torus slices. After a reverse-engineering process that recovers these primitives from triangle meshes, we encode their implicit parameters in a texture that is sent to the GPU. In rendering time, the implicit primitives are visualized seamlessly with other triangles in the scene. The method was tested on two massive industrial models, achieving better performance and image quality while reducing memory use