Integrating Occlusion Culling and Hardware Instancing for Efficient Real-Time Rendering of Building Information Models

This paper presents an efficient approach for integrating occlusion culling and hardware instancing. The work is primarily targeted at Building Information Models (BIM), which typically share characteristics addressed by these two acceleration techniques separately – high level of occlusion and frequent reuse of building components. Together, these two acceleration techniques complement each other and allows large and complex BIMs to be rendered in real-time. Specifically, the proposed method takes advantage of temporal coherence and uses a lightweight data transfer strategy to provide an efficient hardware instancing implementation. Compared to only using occlusion culling, additional speedups of 1.25x-1.7x is achieved for rendering large BIMs received from real-world projects. These speedups are measured in viewpoints that represents the worst case scenarios in terms of rendering performance when only occlusion culling is utilized

A survey of real-time crowd rendering

In this survey we review, classify and compare existing approaches for real-time crowd rendering. We first overview character animation techniques, as they are highly tied to crowd rendering performance, and then we analyze the state of the art in crowd rendering. We discuss different representations for level-of-detail (LoD) rendering of animated characters, including polygon-based, point-based, and image-based techniques, and review different criteria for runtime LoD selection. Besides LoD approaches, we review classic acceleration schemes, such as frustum culling and occlusion culling, and describe how they can be adapted to handle crowds of animated characters. We also discuss specific acceleration techniques for crowd rendering, such as primitive pseudo-instancing, palette skinning, and dynamic key-pose caching, which benefit from current graphics hardware. We also address other factors affecting performance and realism of crowds such as lighting, shadowing, clothing and variability. Finally we provide an exhaustive comparison of the most relevant approaches in the field.Peer ReviewedPostprint (author's final draft

Visibility-Based Optimizations for Image Synthesis

Katedra počítačové grafiky a interakce

Remoção hierárquica de geometria por oclusão em simulações em tempo real

Mestrado em Engenharia Electrotécnica e de ComputadoresAs aplicações de simulação gráfica em tempo real podem apresentar um fraco desempenho devido à elevada complexidade de ambientes virtuais de muito grandes dimensões. Um exemplo é a simulação de condução em ambientes urbanos onde se utilizam cenas extensas com densidade de geometria tipicamente muito elevada. Nesta perspectiva, o desenvolvimento de métodos que permitem a selecção apenas da geometria visível, eliminado toda a restante, é de importância crucial pois irá diminuir a quantidade de trabalho a realizar pelo hardware gráfico na geração da imagem final apresentada ao utilizador. Neste grupo de métodos, que determinam a visibilidade da geometria mediante um ponto de vista sobre a cena, existe um conjunto cujo propósito é o de determinar se um dado objecto no ambiente virtual se encontra ocluso por outro(s), logo, não visível. Este tipo de algoritmos de remoção por oclusão, em particular os que usam Hardware Occlusion Queries, tornou atractiva a determinação de visibilidade em tempo real sem necessidade de extensos cálculos em pré‐processamento. Nesta dissertação é abordada a influência que a aplicação da remoção hierárquica por oclusão tem em simulações de ambientes virtuais complexos de muito grandes dimensões. Para comprovar de forma prática a análise efectuada, foi desenvolvida uma aplicação que usa as funcionalidades base que a API OpenSceneGraph disponibiliza para o render da cena e determinação de visibilidade. É proposto um conjunto de directivas a ter em consideração na aplicação da remoção por oclusão em estruturas hierárquicas de cenas com diferentes níveis de complexidade. Estas directivas são suportadas por resultados experimentais obtidos nas simulações realizadas. Propõe‐se também um melhoramento da API OpenSceneGraph que permite resolver algumas das limitações do algoritmo de remoção por oclusão original disponibilizado pela API

Efficient From-Point Visibility for Global Illumination in Virtual Scenes with Participating Media

Sichtbarkeitsbestimmung ist einer der fundamentalen Bausteine fotorealistischer Bildsynthese. Da die Berechnung der Sichtbarkeit allerdings äußerst kostspielig zu berechnen ist, wird nahezu die gesamte Berechnungszeit darauf verwendet. In dieser Arbeit stellen wir neue Methoden zur Speicherung, Berechnung und Approximation von Sichtbarkeit in Szenen mit streuenden Medien vor, die die Berechnung erheblich beschleunigen, dabei trotzdem qualitativ hochwertige und artefaktfreie Ergebnisse liefern

Occlusion culling et pipeline hybride CPU/GPU pour le rendu temps réel de scènes complexes pour la réalité virtuelle mobile

Le rendu 3D temps réel est devenu ces dernières années un outil indispensable pour tous travaux de modélisation et de maintenance des systèmes mécaniques complexes, pour le développement des jeux sérieux ou ludiques et plus généralement pour toute application de visualisation interactive dans l'industrie, la médecine, l'architecture,... Actuellement, c'est le domaine de prédilection des cartes graphiques en raison de leur architecture spécifiquement conçue pour effectuer des rendus 3D rapides, en particulier grâce à leurs unités de discrétisation et de texture dédiées. Cependant, les applications industrielles sont exécutées sur une large gamme d'ordinateurs, hétérogènes en terme de puissance de calcul. Ces machines ne disposent pas toujours de composants matériels haut de gamme, ce qui restreint leur utilisation pour les applications proposant l'affichage de scènes 3D complexes. Les recherches actuelles sont fortement orientées vers des solutions basées sur les capacités de calcul des cartes graphiques modernes, de haute performance. Au contraire, nous ne supposons pas l'existence systématique de telles cartes sur toutes les architectures et proposons donc d'ajuster notre pipeline de rendu à celles-ci afin d'obtenir un rendu efficace. Notre moteur de rendu s'adapte aux capacités de l'ordinateur, tout en prenant en compte chaque unité de calcul, CPU et GPU. Le but est d'équilibrer au mieux la charge de travail des deux unités afin de permettre un rendu temps réel des scènes complexes, même sur des ordinateurs bas de gamme. Ce pipeline est aisément intégrable à tout moteur de rendu classique et ne nécessite aucune étape de précalculNowadays, 3D real-time rendering has become an essential tool for any modeling work and maintenance of industrial equipment, for the development of serious or fun games, and in general for any visualization application in the domains of industry, medical care, architecture,... Currently, this task is generally assigned to graphics hardware, due to its specific design and its dedicated rasterization and texturing units. However, in the context of industrial applications, a wide range of computers is used, heterogeneous in terms of computation power. These architectures are not always equipped with high-end hardware, which may limit their use for this type of applications. Current research is strongly oriented towards modern high performance graphics hardware-based solutions. On the contrary, we do not assume the existence of such hardware on all architectures. We propose therefore to adapt our pipeline according to the computing architecture in order to obtain an efficient rendering. Our pipeline adapts to the computer's capabilities, taking into account each computing unit, CPU and GPU. The goal is to provide a well-balanced load on the two computing units, thus ensuring a real-time rendering of complex scenes, even on low-end computers. This pipeline can be easily integrated into any conventional rendering system and does not require any precomputation ste