Tessellated Voxelization for Global Illumination using Voxel Cone Tracing

Modeling believable lighting is a crucial component of computer graphics applications, including games and modeling programs. Physically accurate lighting is complex and is not currently feasible to compute in real-time situations. Therefore, much research is focused on investigating efficient ways to approximate light behavior within these real-time constraints. In this thesis, we implement a general purpose algorithm for real-time applications to approximate indirect lighting. Based on voxel cone tracing, we use a filtered representation of a scene to efficiently sample ambient light at each point in the scene. We present an approach to scene voxelization using hardware tessellation and compare it with an approach utilizing hardware rasterization. We also investigate possible methods of warped voxelization. Our contributions include a complete and open-source implementation of voxel cone tracing along with both voxelization algorithms. We find similar performance and quality with both voxelization algorithms

Many-Light Real-Time Global Illumination using Sparse Voxel Octree

Global illumination (GI) rendering simulates the propagation of light through a 3D volume and its interaction with surfaces, dramatically increasing the fidelity of computer generated images. While off-line GI algorithms such as ray tracing and radiosity can generate physically accurate images, their rendering speeds are too slow for real-time applications. The many-light method is one of many novel emerging real-time global illumination algorithms. However, it requires many shadow maps to be generated for Virtual Point Light (VPL) visibility tests, which reduces its efficiency. Prior solutions restrict either the number or accuracy of shadow map updates, which may lower the accuracy of indirect illumination or prevent the rendering of fully dynamic scenes. In this thesis, we propose a hybrid real-time GI algorithm that utilizes an efficient Sparse Voxel Octree (SVO) ray marching algorithm for visibility tests instead of the shadow map generation step of the many-light algorithm. Our technique achieves high rendering fidelity at about 50 FPS, is highly scalable and can support thousands of VPLs generated on the fly. A survey of current real-time GI techniques as well as details of our implementation using OpenGL and Shader Model 5 are also presented

Light Propagation Volumes

Tato práce se zabývá problémem výpočtu globálního osvětlení v reálném čase a jsou v ní popsány dvě metody. Reflective Shadow Maps a Light Propagation Volumes. První z nich řeší daný problém rozšířením Shadow mapping algoritmu. Zatímco druhá pokryje scénu 3D mřížkou a za použití sférických harmonických funkcí spočítá šíření světla ve scéně. Dále tato práce obsahuje výsledky měření rychlosti vykreslení algoritmu Light Propagation Volumes stejně jako vyhodnocení vizuální kvality výstupu.This thesis deals with problem of computation of global illumination in real-time. Two methods are described. Namely Reflective Shadow Maps and Light Propagation Volumes. The first of them deals with the problem by using extended Shadow Mapping algorithm. The second one uses scene embedded into a 3D grid together with Spherical harmonics to compute light propagation in the scene. Furthermore this thesis contains results of measurement of the rendering speed of the Light Propagation Volumes algorithm with various settings on several machines. Quality of the resulting output of the algorithm is also evaluated.

Photon Splatting Using a View-Sample Cluster Hierarchy

Splatting photons onto primary view samples, rather than gathering from a photon acceleration structure, can be a more efficient approach to evaluating the photon-density estimate in interactive applications, where the number of photons is often low compared to the number of view samples. Most photon splatting approaches struggle with large photon radii or high resolutions due to overdraw and insufficient culling. In this paper, we show how dynamic real-time diffuse interreflection can be achieved by using a full 3D acceleration structure built over the view samples and then splatting photons onto the view samples by traversing this data structure. Full dynamic lighting and scenes are possible by tracing and splatting photons, and rebuilding the acceleration structure every frame. We show that the number of view-sample/photon tests can be significantly reduced and suggest further culling techniques based on the normal cone of each node in the hierarchy. Finally, we present an approximate variant of our algorithm where photon traversal is stopped at a fixed level of our hierarchy, and the incoming radiance is accumulated per node and direction, rather than per view sample. This improves performance significantly with little visible degradation of quality

Flux-Limited Diffusion for Multiple Scattering in Participating Media

For the rendering of multiple scattering effects in participating media, methods based on the diffusion approximation are an extremely efficient alternative to Monte Carlo path tracing. However, in sufficiently transparent regions, classical diffusion approximation suffers from non-physical radiative fluxes which leads to a poor match to correct light transport. In particular, this prevents the application of classical diffusion approximation to heterogeneous media, where opaque material is embedded within transparent regions. To address this limitation, we introduce flux-limited diffusion, a technique from the astrophysics domain. This method provides a better approximation to light transport than classical diffusion approximation, particularly when applied to heterogeneous media, and hence broadens the applicability of diffusion-based techniques. We provide an algorithm for flux-limited diffusion, which is validated using the transport theory for a point light source in an infinite homogeneous medium. We further demonstrate that our implementation of flux-limited diffusion produces more accurate renderings of multiple scattering in various heterogeneous datasets than classical diffusion approximation, by comparing both methods to ground truth renderings obtained via volumetric path tracing.Comment: Accepted in Computer Graphics Foru

Tone Mapping and white balancing for walkthrough

Ce rapport décrit nos travaux traitant du renforcement perspectif de rendu produit par des moteurs d'illumination globale. L'objectif du stage est de produire une technique prenant en compte les différents aspects du système visuel humain pour les rendus de synthèse interactif

Стан та перспективи подальших досліджень сфери обчислення глобального освітлення у реальному часі

Currently, computer graphics is a very important part of computer science. Graphics-related developments have been used in many different situations, for example, in animated and cinema movie productions, in computer graphics applications, modeling, and simulation systems, for different visualizations in medicine, mathematics, physics, etc. One of the main problems of computer graphics is the task of transforming the information of some imaginary scene and its observer into a photorealistic image of this scene for them. Solving this problem is very important, but right now obtaining a good quality result is possible only in a non-interactive scenario (for example, in animated films), while in real-time (for example, in computer modeling or simulations, in computer games) it is usually necessary to use some approximate algorithms. Although these algorithms are often able to provide a natural-looking result, they still have plenty of very noticeable inaccuracies. However, this topic is gaining more and more development recently due to the improvement of graphics processors. In addition to a significant increase in computation speed and the number of cores, the appearance of ray tracing hardware acceleration plays a large role. Global illumination computation is an inseparable part of photorealistic image generation. This paper is focused on solving this problem in real-time, which means developing a system capable of generating such images at a speed sufficient for the resulting sequence to be perceived by a person as a smooth animation. We give the theoretical information required for understanding this problem and describe existing methods and algorithms for solving it with their advantages and disadvantages. Also based on an overview of the topic's current state, we analyze further research prospects and directions for improving existing and developing new methods of real-time global illumination calculation, while considering compute power and technologies of the latest graphics hardware. Pages of the article in the issue: 72 - 79 Language of the article: UkrainianУ статті розглядається така проблема сучасної комп’ютерної графіки як обчислення глобального освітлення в реальному часі. Глобальне освітлення є невід’ємною частиною фотореалістичного рендерінгу, але його підрахунок потребує доволі об’ємних обчислень. Через це на даний момент якісне глобальне освітлення існує лише у неінтерактивних рендерах (наприклад, у мультиплікаційних фільмах), а у реальному часі (наприклад, комп’ютерному моделюванні або симуляціях, комп’ютерних іграх) зазвичай використовуються певні наближення, які хоч і надають зображенню певну природність, але все одно мають вкрай помітні неточності. Але останнім часом дана тема набуває все більшого розвитку за рахунок удосконалення відеопроцессорів. Крім значного підвищення їх швидкодії та збільшення кількості ядер досить велику роль грає поява апаратного прискорення трасування променів. В даній роботі проводиться теоретичне дослідження проблеми глобального освітлення, наводяться існуючи підходи та розробки для вирішення даної проблеми та аналізуються перспективи подальших досліджень та розробки нових методів обчислення глобального освітлення в реальному часі з урахуванням новітніх апаратних можливостей обчислювальної техніки

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