Analytic Approximations for Real-Time Area Light Shading Lecocq, Pascal; Dufay, Arthur; Sourimant, Gael ...
IEEE transactions on visualization and computer graphics,
2017-May-1, 2017-05-00, 2017-5-1, 20170501, Letnik:
23, Številka:
5
Journal Article
Recenzirano
We introduce analytic approximations for accurate real-time rendering of surfaces lit by non-occluded area light sources. Our solution leverages the Irradiance Tensors developed by Arvo for the ...shading of Phong surfaces lit by a polygonal light source. Using a reformulation of the 1D boundary edge integral, we develop a general framework for approximating and evaluating the integral in constant time using simple peak shape functions. To overcome the Phong restriction, we propose a low cost edge splitting strategy that accounts for the spherical warp introduced by the half vector parametrization. Thanks to this novel extension, we accurately approximate common microfacet BRDFs, providing a practical method producing specular stretches that closely match the ground truth in real-time. Finally, using the same approximation framework, we introduce support for spherical and disc area light sources, based on an original polygon spinning method supporting non-uniform scaling operations and horizon clipping. Implemented on a GPU, our method achieves real-time performances without any assumption on area light shape nor surface roughness.
We introduce analytic approximations for accurate real-time rendering of surfaces lit by non-occluded area light sources. Our solution leverages the Irradiance Tensors developed by Arvo for the ...shading of Phong surfaces lit by a polygonal light source. Using a reformulation of the 1D boundary edge integral, we develop a general framework for approximating and evaluating the integral in constant time using simple peak shape functions. To overcome the Phong restriction, we propose a low cost edge splitting strategy that accounts for the spherical warp introduced by the half vector parametrization. Thanks to this novel extension, we accurately approximate common microfacet BRDFs, providing a practical method producing specular stretches that closely match the ground truth in real-time. Finally, using the same approximation framework, we introduce support for spherical and disc area light sources, based on an original polygon spinning method supporting non-uniform scaling operations and horizon clipping. Implemented on a GPU, our method achieves real-time performances without any assumption on area light shape nor surface roughness.
La génération d'images de synthèse pour la production cinématographique n'a cessé d'évoluer durant ces dernières décennies. Pour le non-expert, il semble que les effets spéciaux aient atteint un ...niveau de réalisme ne pouvant être dépassé. Cependant, les logiciels mis à la disposition des artistes ont encore du progrès à accomplir. En effet, encore trop de temps est passé à attendre le résultat de longs calculs, notamment lors de la prévisualisation d'effets spéciaux. La lenteur ou la mauvaise qualité des logiciels de prévisualisation pose un réel problème aux artistes. Cependant, l'évolution des cartes graphiques ces dernières années laisse espérer une potentielle amélioration des performances de ces outils, notamment par la mise en place d'algorithmes hybrides rasterisation/ lancer de rayons, tirant profit de la puissance de calcul de ces processeurs, et ce, grâce à leur architecture massivement parallèle. Cette thèse explore les différentes briques logicielles nécessaires à la mise en place d'un pipeline de rendu complexe sur carte graphique, permettant une meilleure prévisualisation des effets spéciaux. Différentes contributions ont été apportées à l'entreprise durant cette thèse. Tout d'abord, un pipeline de rendu hybride a été développé (cf. Chapitre 2). Par la suite, différentes méthodes d'implémentation de l'algorithme de Path Tracing ont été testées (cf. Chapitre 3), de façon à accroître les performances du pipeline de rendu sur GPU. Une structure d'accélération spatiale a été implémentée (cf. Chapitre 4), et une amélioration de l'algorithme de traversée de cette structure sur GPU a été proposée (cf. Section 4.3.2). Ensuite, une nouvelle méthode de décorrélation d'échantillons, dans le cadre de la génération de nombres aléatoires a été proposée (cf. Section 5.4) et a donné lieu à une publication Dufay et al., 2016. Pour finir, nous avons tenté de combiner l'algorithme de Path Tracing et les solutions Many Lights, toujours dans le but d'améliorer la prévisualisation de l'éclairage global. Cette thèse a aussi donné lieu à la soumission de trois mémoires d'invention et a permis le développement de deux outils logiciels présentés en Annexe A.
Image synthesis for movie production never stopped evolving over the last decades. It seems it has reached a level of realism that cannot be outperformed. However, the software tools available for visual effects (VFX) artists still need to progress. Indeed, too much time is still wasted waiting for results of long computations, especially when previewing VFX. The delays or poor quality of previsualization software poses a real problem for artists. However, the evolution of graphics processing units (GPUs) in recent years suggests a potential improvement of these tools. In particular, by implementing hybrid rasterization/ray tracing algorithms, taking advantage of the computing power of these processors and their massively parallel architecture. This thesis explores the different software bricks needed to set up a complex rendering pipeline on the GPU, that enables a better previsualization of VFX. Several contributions have been brought during this thesis. First, a hybrid rendering pipeline was developed (cf. Chapter 2). Subsequently, various implementation schemes of the Path Tracing algorithm have been tested (cf. Chapter 3), in order to increase the performance of the rendering pipeline on the GPU. A spatial acceleration structure has been implemented (cf. Chapter 4), and an improvement of the traversal algorithm of this structure on GPU has been proposed (cf. Section 4.3.2). Then, a new sample decorrelation method, in the context of random number generation was proposed (cf. Section 5.4) and resulted in a publication Dufay et al., 2016. Finally, we combined the Path Tracing algorithm with the Many Lights solution, always with the aim of improving the preview of global illumination. This thesis also led to the submission of three patents and allowed the development of two software tools presented in Appendix A.
Nanostructured materials have recently emerged as a promising approach for material appearance design. Research has mainly focused on creating structural colours by wave interference, leaving aside ...other important aspects that constitute the visual appearance of an object, such as the respective weight of specular and diffuse reflectances, object macroscopic shape, illumination and viewing conditions. Here, we report the potential of disordered optical metasurfaces for harnessing visual appearance. We develop a multiscale modelling platform for the predictive rendering of macroscopic objects covered by metasurfaces in realistic settings, showing how nanoscale resonances and mesoscale interferences can be used to spectrally and angularly shape reflected light and thus create unusual visual effects at the macroscale. We validate this property with realistic synthetic images of macroscopic objects and centimetre-scale samples observable with the naked eye. This framework opens new perspectives in many branches of fine and applied visual arts.
Metasurfaces have flourished in the last few years thanks to their extraordinary capabilities in the manipulation of light. In this work, we propose a theoretical tools and models that can ...effectively and intuitively predict the visual appearance of disordered resonant metasurfaces and compare their predictions with experimental results.
Two versions of an operational giant magnetoimpedance (GMI)-based magnetometer, one of which is capable of working in an unshielded geomagnetic field, has been design, built and benchmarked against a ...commercial fluxgate magnetometer. The sensing element consists of a detection coil, strongly coupled to the GMI wire, in a two-port configuration. Its optimization is based on the surface impedance tensor of the sensing element, in which we include parasitic capacitance and geometric parameters of the coil. Conditions for optimizing the electronic noise level are deduced from the model recently published in (IEEE Sensors Journal, vol. 11, no. 6, pp. 1317-1324, 2011.). The optimized sensor and its conditioning electronics are operated in a field-locked loop, using an external coil or the detection coil for feedback. Experimental noise performance correlates well with that expected from the sensitivity and noise models and are comparable to those of a commercial Flux-Gate magnetometer, offering a low-cost solution for high sensitivity magnetometry. However, the proposed GMI magnetometers still exhibit significant 1/ f noise.
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