Cinema Darkroom: A Deferred Rendering Framework for Large-Scale Datasets

This paper presents a framework that fully leverages the advantages of a deferred rendering approach for the interactive visualization of large-scale datasets. Geometry buffers (G-Buffers) are generated and stored in situ, and shading is performed post hoc in an interactive image-based rendering front end. This decoupled framework has two major advantages. First, the G-Buffers only need to be computed and stored once---which corresponds to the most expensive part of the rendering pipeline. Second, the stored G-Buffers can later be consumed in an image-based rendering front end that enables users to interactively adjust various visualization parameters---such as the applied color map or the strength of ambient occlusion---where suitable choices are often not known a priori. This paper demonstrates the use of Cinema Darkroom on several real-world datasets, highlighting CD's ability to effectively decouple the complexity and size of the dataset from its visualization

Ambient Occlusion on Mobile: an empirical comparison

In this thesis, we study the feasibility of screen space ambient occlusion on a range of mobile devices. We implement several of the most popular techniques and propose two rendering pipelines, a custom algorithm and an optimisation that can be applied to any algorithm to speed up computation times

Combined surface and volumetric occlusion shading

Journal ArticleIn this paper, a method for interactive direct volume rendering is proposed that computes ambient occlusion effects for visualizations that combine both volumetric and geometric primitives, specifically tube shaped geometric objects representing streamlines, magnetic field lines or DTI fiber tracts. The proposed algorithm extends the recently proposed Directional Occlusion Shading model to allow the rendering of those geometric shapes in combination with a context providing 3D volume, considering mutual occlusion between structures represented by a volume or geometry

Ambient Occlusion

Import 05/08/2014Tématem diplomové práce je pochopení a následná implementace nejpoužívanějších algoritmů, které slouží k výpočtu zastínění okolím ve 3D scéně. Zastínění bodu scény okolím udává množství světla dopadajícího do daného bodu, což způsobuje zatemnění rohů objektů a kontaktní stíny mezi objekty. Toto zastínění je dílčím jevem globálního osvětlení. Proto je první část práce zaměřena na metody, které počítají globální osvětlení nebo jeho části. Ve druhé části práce se věnuji přímo zastínění okolím. Počínaje zmíněním první metody počítající zastínění v každém bodě 3D scény, až po nejpoužívanější aproximace tohoto jevu, které pracují nad informacemi o pixelech obrazu získanými během vykreslování.The topic of this diploma thesis is understanding and subsequent implementation of the most widely used algorithms that are used to calculate ambient occlusion in a 3D scene. Occlusion of a point in scene indicates the amount of light reaching to that point, which causes darkening the corners of objects and contact shadows between objects. This occlusion is a partial phenomenon of global illumination. Therefore, the first part of this thesis is focused on methods that calculate global illumination or its part. The second part is devoted directly to ambient occlusion. Starting by mentioning the first method that calculates occlusion at each point in a 3D scene, to the most commonly used approximation of this phenomenon, which operate over information about pixels of image acquired during rendering.460 - Katedra informatikyvýborn

Evaluating Tessellation and Screen-Space Ambient Occlusion in WebGL-Based Real-Time Application

abstract: Tessellation and Screen-Space Ambient Occlusion are algorithms which have been widely-used in real-time rendering in the past decade. They aim to enhance the details of the mesh, cast better shadow effects and improve the quality of the rendered images in real time. WebGL is a web-based graphics library derived from OpenGL ES used for rendering in web applications. It is relatively new and has been rapidly evolving, this has resulted in it supporting a subset of rendering features normally supported by desktop applications. In this thesis, the research is focusing on evaluating Curved PN-Triangles tessellation with Screen Space Ambient Occlusion (SSAO), Horizon-Based Ambient Occlusion (HBAO) and Horizon-Based Ambient Occlusion Plus (HBAO+) in WebGL-based real-time application and comparing its performance to desktop based application and to discuss the capabilities, limitations and bottlenecks of WebGL 1.0.Dissertation/ThesisWebGL ProgramOpenGL ProgramMasters Thesis Computer Science 201

Gerçek zamanlı sahnelerin ışıklandırılmasına yardımcı, dinamik voxelleştirme teknikleri.

In this thesis, we focus on approximating indirect illumination on real-time applications to visualize realistic scenes. In order to approximate indirect illumination we provide a fast sparse voxel tree structure for highly dynamic scenes. Our system tries to cover traditional real-time animation methods including dynamic non-deforming objects and objects that deform with bone transformations. The voxel scene data structure is designed for fully dynamic objects and eliminates the voxelization of the dynamic objects per frame which in turn facilitates efficient realistic rendering. We combine this new scene information structure with the widely used real-time rendering techniques and these techniques’ data structures such as shadow mapping and deferred rendering to provide an efficient cone ray-casting algorithm that achieves global illumination in real-time. M.S. - Master of Scienc

Logarithme d'harmoniques sphériques pour le rendu d'ombres douces de champs de hauteurs et de maillages

Les ombres sont un élément important pour la compréhension d'une scène. Grâce à elles, il est possible de résoudre des situations autrement ambigües, notamment concernant les mouvements, ou encore les positions relatives des objets de la scène. Il y a principalement deux types d'ombres: des ombres dures, aux limites très nettes, qui résultent souvent de lumières ponctuelles ou directionnelles; et des ombres douces, plus floues, qui contribuent à l'atmosphère et à la qualité visuelle de la scène. Les ombres douces résultent de grandes sources de lumière, comme des cartes environnementales, et sont difficiles à échantillonner efficacement en temps réel. Lorsque l'interactivité est prioritaire sur la qualité, des méthodes d'approximation peuvent être utilisées pour améliorer le rendu d'une scène à moindre coût en temps de calcul. Nous calculons interactivement les ombres douces résultant de sources de lumière environnementales, pour des scènes composées d'objets en mouvement et d'un champ de hauteurs dynamique. Notre méthode enrichit la méthode d'exponentiation des harmoniques sphériques, jusque là limitée aux bloqueurs sphériques, pour pouvoir traiter des champs de hauteurs. Nous ajoutons également une représentation pour les BRDFs diffuses et glossy. Nous pouvons ainsi combiner les visibilités et BRDFs dans un même espace, afin de calculer efficacement les ombres douces et les réflexions de scènes complexes. Un algorithme hybride, qui associe les visibilités en espace écran et en espace objet, permet de découpler la complexité des ombres de la complexité de la scène.Shadows provide important visual cues to a viewer about the relative positions of objects in a scene, as well as certain properties of the lighting in an environment, such as orientation, size, and intensity. The importance of shadows in visual simulations is even more striking when any element of an environment, such as characters in a scene or the light sources themselves, are animated over time. The simulation of so-called "hard" shadows from small point or directional light sources is a very mature field in computer graphics, with many concrete and well-established solutions. On the other hand, efficiently approximating the shadowing effects from larger "area" light sources, such as ceiling lights or environment maps captured from the real world, remains an open problem. Indeed, in many applications, the availability of a high-performance solution to this problem trumps the need for an accurate solution. Our work aims to solve the problem of approximating soft shadows interactively, in scenes where the geometric elements and lighting are both allowed to be animated over time. We decompose dynamic scene elements into deformable objects, approximated with a collection of non-deformable animated spheres, and height field geometry. By leveraging a novel spherical harmonic basis-space exponentiation formulation, we are able to very quickly accumulate the shadowing effects from these many dynamic blockers, while also encoding their local reflectance behaviour in a similar reduced basis representation. Our proof-of-concept implementation uses a hybrid, multi-resolution image- and object-space visibility marching algorithm that decouples geometric complexity from radiometric complexity. We demonstrate our method on several scenes with dynamic blockers and complex illumination

An empirical evaluation of document embeddings and similarity metrics for scientific articles

The comparison of documents—such as articles or patents search, bibliography recommendations systems, visualization of document collections, etc.—has a wide range of applications in several fields. One of the key tasks that such problems have in common is the evaluation of a similarity metric. Many such metrics have been proposed in the literature. Lately, deep learning techniques have gained a lot of popularity. However, it is difficult to analyze how those metrics perform against each other. In this paper, we present a systematic empirical evaluation of several of the most popular similarity metrics when applied to research articles. We analyze the results of those metrics in two ways, with a synthetic test that uses scientific papers and Ph.D. theses, and in a real-world scenario where we evaluate their ability to cluster papers from different areas of research.This research was funded by Project TIN2017-88515-C2-1-R funded by Ministerio de Economía y Competitividad, under MCIN/AEI/10.13039/501100011033/FEDER “A way to make Europe”.Peer ReviewedPostprint (published version

Ambient occlusion and shadows for molecular graphics

Computer based visualisations of molecules have been produced as early as the 1950s to aid researchers in their understanding of biomolecular structures. An important consideration for Molecular Graphics software is the ability to visualise the 3D structure of the molecule in a clear manner. Recent advancements in computer graphics have led to improved rendering capabilities of the visualisation tools. The capabilities of current shading languages allow the inclusion of advanced graphic effects such as ambient occlusion and shadows that greatly improve the comprehension of the 3D shapes of the molecules. This thesis focuses on finding improved solutions to the real time rendering of Molecular Graphics on modern day computers. The methods of calculating ambient occlusion and both hard and soft shadows are examined and implemented to give the user a more complete experience when navigating large molecular structures