Rendering of light shaft and shadow for indoor environments enhancing technique

The ray marching methods have become the most attractive method to provide realism in rendering the effects of light scattering in the participating media of numerous applications. This has attracted significant attention from the scientific community. Up-sampling of ray marching methods is suitable to evaluate light scattering effects such as volumetric shadows and light shafts for rendering realistic scenes, but suffers of cost a lot for rendering. Therefore, some encouraging outcomes have been achieved by using down-sampling of ray marching approach to accelerate rendered scenes. However, these methods are inherently prone to artifacts, aliasing and incorrect boundaries due to the reduced number of sample points along view rays. This study proposed a new enhancing technique to render light shafts and shadows taking into consideration the integration light shafts, volumetric shadows, and shadows for indoor environments. This research has three major phases that cover species of the effects addressed in this thesis. The first phase includes the soft volumetric shadows creation technique called Soft Bilateral Filtering Volumetric Shadows (SoftBiF-VS). The soft shadow was created using a new algorithm called Soft Bilateral Filtering Shadow (SBFS). This technique was started by developing an algorithm called Imperfect Multi-View Soft Shadows (IMVSSs) based on down-sampling multiple point lights (DMPLs) and multiple depth maps, which are processed by using bilateral filtering to obtain soft shadows. Then, down-sampling light scattering model was used with (SBFS) to create volumetric shadows, which was improved using cross-bilateral filter to get soft volumetric shadows. In the second phase, soft light shaft was generated using a new technique called Realistic Real-Time Soft Bilateral Filtering Light Shafts (realTiSoftLS). This technique computed the light shaft depending on down-sampling volumetric light model and depth test, and was interpolated by bilateral filtering to gain soft light shafts. Finally, an enhancing technique for integrating all of these effects that represent the third phase of this research was achieved. The performance of the new enhanced technique was evaluated quantitatively and qualitatively a measured using standard dataset. Results from the experiment showed that 63% of the participants gave strong positive responses to this technique of improving realism. From the quantitative evaluation, the results revealed that the technique has dramatically outpaced the stateof- the-art techniques with a speed of 74 fps in improving the performance for indoor environments

Lancer de photons multi-passes et écrasement de photons pour le rendu optronique

La simulation de l'éclairage par illumination globale a fait l'objet de nombreuses recherches et applications au cours des dernières années. Tout d'abord utilisée dans le domaine visible, la simulation est aujourd'hui de plus en plus appliquée au rendu infrarouge. On appelle optronique l'union de ces deux domaines. Le problème principal des méthodes d'illumination globale actuelles provient de la difficulté à traiter le phénomène de diffusion de la lumière, aussi bien dans le cas des surfaces que des milieux participants. Ces méthodes offrent des résultats satisfaisants dans le cas de scènes simples, mais les performances s'effrondrent lorsque la complexité augmente. Dans la première partie de cette thèse, nous exposons la nécessité de la prise en compte des phénomènes de diffusion pour la simulation optronique. Dans la deuxième partie nous posons les équations qui unifient les différentes méthodes de synthèse d'image, c'est à dire l'équation du rendu et l'équation volumique du transfert radiatif. L'état de l'art des méthodes d'illumination globale présenté dans la troisième partie montre qu'à l'heure actuelle la méthode des cartes de photons est celle qui offre le meilleur compromis performance/qualité. Néanmoins, la qualité des résultats obtenus grâce à cette méthode est dépendante du nombre de photons qui peuvent être stockés et donc de la quantité de mémoire disponible. Dans la quatrième partie de la thèse, nous proposons une évolution de la méthode, le lancer de photons multi-passes, qui permet de lever cette dépendance mémoire, et ainsi d'obtenir une très grande qualité sans pour autant utiliser une configuration matérielle onéreuse. Un autre problème de la méthode des cartes de photons est le temps de calcul important nécessaire lors du rendu de milieux participants. Dans la cinquième et dernière partie de cette thèse, nous proposons une méthode, l'écrasement de photons volumique, qui prend avantage de l'estimation de densité pour reconstruire efficacement la luminance volumique à partir de la carte de photons. Notre idée est d'isoler le calcul de la diffusion et d'utiliser une approche duale de l'estimation de densité pour l'optimiser car il constitue la partie coûteuse du calcul. Bien que les temps de rendu obtenus par notre méthode sont meilleurs que ceux obtenus en utilisant la méthode des cartes de photons pour la même qualité, nous proposons aussi une optimisation de la méthode utilisant les nouvelles capacités des cartes graphiques.Much research have been done on global illumination simulation. Firstly used in the visible spectrum domain, today, simulation is more and more applied to infrared rendering. The union of these two domains is called optronic. The main problem of the current global illumination methods comes from the complexity of the light scattering phenomena, as well for surfaces as for participating media. These methods offer satisfactory results for simple scenes, but performances crash when complexity raises. In the first part of this thesis, we expose the necessity to take scattering phenomena into account for optronic simulation. In the second part, we pose the equations that unify all global illumination methods, i.e. the rendering equation and the volume radiative tranfer equation. The state of the art presented in the third part shows that the Photon Mapping method is, at this moment, the one that offers the better compromise between performance and quality. Nevertheless, the quality of the results obtained with this method depends on the number of photons that can be stocked, and then on the available memory. In the fourth part, we propose an evolution of the method, called Multipass Photon Mapping, which permits to get rid of this memory dependency, and hence, to achieve a great accuracy without using a costly harware configuration. Another problem inherent to Photon Mapping, is the enormous rendering time needed for participating media rendering. In the fifth and last part of this thesis, we propose a method, called Volume Photon Splatting, which takes advantage of density estimation to efficiently reconstruct volume radiance from the photon map. Our idea is to separate the computation of emission, absorption and out-scattering from the computation of in-scattering. Then we use a dual approach of density estimation to optimize this last part as it is the most computational expensive. Our method extends Photon Splatting, which optimizes the computation time of Photon Mapping for surface rendering, to participating media, and then considerably reduce participating media rendering times. Even though our method is faster than Photon Mapping for equal quality, we also propose a GPU based optimization of our algorithm