9 research outputs found
A Dual-Beam Method-of-Images 3D Searchlight BSSRDF
We present a novel BSSRDF for rendering translucent materials. Angular
effects lacking in previous BSSRDF models are incorporated by using a dual-beam
formulation. We employ a Placzek's Lemma interpretation of the method of images
and discard diffusion theory. Instead, we derive a plane-parallel
transformation of the BSSRDF to form the associated BRDF and optimize the image
confiurations such that the BRDF is close to the known analytic solutions for
the associated albedo problem. This ensures reciprocity, accurate colors, and
provides an automatic level-of-detail transition for translucent objects that
appear at various distances in an image. Despite optimizing the subsurface
fluence in a plane-parallel setting, we find that this also leads to fairly
accurate fluence distributions throughout the volume in the original 3D
searchlight problem. Our method-of-images modifications can also improve the
accuracy of previous BSSRDFs.Comment: added clarifying text and 1 figure to illustrate the metho
Theory and numerical integration of subsurface light transport
En synthèse d’images, reproduire les effets complexes de la lumière sur des matériaux transluminescents, tels que la cire, le marbre ou la peau, contribue grandement au réalisme d’une image. Malheureusement, ce réalisme supplémentaire est couteux en temps de calcul. Les modèles basés sur la théorie de la diffusion visent à réduire ce coût en simulant le comportement physique du transport de la lumière sous surfacique tout en imposant des contraintes de variation sur la lumière incidente et sortante. Une composante importante de ces modèles est leur application à évaluer hiérarchiquement l’intégrale numérique de l’illumination sur la surface d’un objet.
Cette thèse révise en premier lieu la littérature actuelle sur la simulation réaliste de la transluminescence, avant d’investiguer plus en profondeur leur application et les extensions des modèles de diffusion en synthèse d’images. Ainsi, nous proposons et évaluons une nouvelle technique d’intégration numérique hiérarchique utilisant une nouvelle analyse fréquentielle de la lumière sortante et incidente pour adapter efficacement le taux d’échantillonnage pendant l’intégration. Nous appliquons cette théorie à plusieurs modèles qui correspondent à l’état de l’art en diffusion, octroyant une amélioration possible à leur efficacité et précision.In image synthesis, reproducing the complex appearance of objects with subsurface light
scattering, such as wax, marble and skin, greatly contributes to the realism of an image.
Unfortunately, this added realism comes at a high computational cost. Models based on
diffusion theory aim to reduce this computational cost by simulating the physical behaviour of
subsurface light scattering while imposing smoothness constraints on the incident and outgoing
light fields. An important component of these models is how they are employed to hierarchically
evaluate the numerical integral of lighting over the surface of an object.
This thesis will first review the existing literature on realistic subsurface lighting simulation,
before investigating in more depth the application and extension of modern diffusion models in
image synthesis. In doing so, we propose and evaluate a new hierarchical numerical integration
technique that uses a novel frequency analysis of the incident and outgoing light fields to reliably
adapt the sampling rate during integration. We realize our resulting theory in the context of
several state-of-the-art diffusion models, providing a marked improvement in their efficiency
and accuracy
A Frequency Analysis and Dual Hierarchy for Efficient Rendering of Subsurface Scattering
International audienceBSSRDFs are commonly used to model subsurface light transport in highly scattering media such as skin and marble. Rendering with BSSRDFs requires an additional spatial integration, which can be significantly more expensive than surface-only rendering with BRDFs. We introduce a novel hierarchical rendering method that can mitigate this additional spatial integration cost. Our method has two key components: a novel frequency analysis of subsurface light transport, and a dual hierarchy over shading and illumination samples. Our frequency analysis predicts the spatial and angular variation of outgoing radiance due to a BSSRDF. We use this analysis to drive adaptive spatial BSSRDF integration with sparse image and illumination samples. We propose the use of a dual-tree structure that allows us to simultaneously traverse a tree of shade points (i.e., pixels) and a tree of object-space illumination samples. Our dual-tree approach generalizes existing single-tree accelerations. Both our frequency analysis and the dual-tree structure are compatible with most existing BSSRDF models, and we show that our method improves rendering times compared to the state of the art method of Jensen and Buhler
Digital Light
Light symbolises the highest good, it enables all visual art, and today it lies at the heart of billion-dollar industries. The control of light forms the foundation of contemporary vision. Digital Light brings together artists, curators, technologists and media archaeologists to study the historical evolution of digital light-based technologies. Digital Light provides a critical account of the capacities and limitations of contemporary digital light-based technologies and techniques by tracing their genealogies and comparing them with their predecessor media. As digital light remediates multiple historical forms (photography, print, film, video, projection, paint), the collection draws from all of these histories, connecting them to the digital present and placing them in dialogue with one another.
Light is at once universal and deeply historical. The invention of mechanical media (including photography and cinematography) allied with changing print technologies (half-tone, lithography) helped structure the emerging electronic media of television and video, which in turn shaped the bitmap processing and raster display of digital visual media. Digital light is, as Stephen Jones points out in his contribution, an oxymoron: light is photons, particulate and discrete, and therefore always digital. But photons are also waveforms, subject to manipulation in myriad ways. From Fourier transforms to chip design, colour management to the translation of vector graphics into arithmetic displays, light is constantly disciplined to human purposes. In the form of fibre optics, light is now the infrastructure of all our media; in urban plazas and handheld devices, screens have become ubiquitous, and also standardised. This collection addresses how this occurred, what it means, and how artists, curators and engineers confront and challenge the constraints of increasingly normalised digital visual media.
While various art pieces and other content are considered throughout the collection, the focus is specifically on what such pieces suggest about the intersection of technique and technology. Including accounts by prominent artists and professionals, the collection emphasises the centrality of use and experimentation in the shaping of technological platforms. Indeed, a recurring theme is how techniques of previous media become technologies, inscribed in both digital software and hardware. Contributions include considerations of image-oriented software and file formats; screen technologies; projection and urban screen surfaces; histories of computer graphics, 2D and 3D image editing software, photography and cinematic art; and transformations of light-based art resulting from the distributed architectures of the internet and the logic of the database.
Digital Light brings together high profile figures in diverse but increasingly convergent fields, from academy award-winner and co-founder of Pixar, Alvy Ray Smith to feminist philosopher Cathryn Vasseleu
Digital light
Light symbolises the highest good, it enables all visual art, and today it lies at the heart of billion-dollar industries. The control of light forms the foundation of contemporary vision. Digital Light brings together artists, curators, technologists and media archaeologists to study the historical evolution of digital light-based technologies. Digital Light provides a critical account of the capacities and limitations of contemporary digital light-based technologies and techniques by tracing their genealogies and comparing them with their predecessor media. As digital light remediates multiple historical forms (photography, print, film, video, projection, paint), the collection draws from all of these histories, connecting them to the digital present and placing them in dialogue with one another.Light is at once universal and deeply historical. The invention of mechanical media (including photography and cinematography) allied with changing print technologies (half-tone, lithography) helped structure the emerging electronic media of television and video, which in turn shaped the bitmap processing and raster display of digital visual media. Digital light is, as Stephen Jones points out in his contribution, an oxymoron: light is photons, particulate and discrete, and therefore always digital. But photons are also waveforms, subject to manipulation in myriad ways. From Fourier transforms to chip design, colour management to the translation of vector graphics into arithmetic displays, light is constantly disciplined to human purposes. In the form of fibre optics, light is now the infrastructure of all our media; in urban plazas and handheld devices, screens have become ubiquitous, and also standardised. This collection addresses how this occurred, what it means, and how artists, curators and engineers confront and challenge the constraints of increasingly normalised digital visual media.While various art pieces and other content are considered throughout the collection, the focus is specifically on what such pieces suggest about the intersection of technique and technology. Including accounts by prominent artists and professionals, the collection emphasises the centrality of use and experimentation in the shaping of technological platforms. Indeed, a recurring theme is how techniques of previous media become technologies, inscribed in both digital software and hardware. Contributions include considerations of image-oriented software and file formats; screen technologies; projection and urban screen surfaces; histories of computer graphics, 2D and 3D image editing software, photography and cinematic art; and transformations of light-based art resulting from the distributed architectures of the internet and the logic of the database.Digital Light brings together high profile figures in diverse but increasingly convergent fields, from academy award-winner and co-founder of Pixar, Alvy Ray Smith to feminist philosopher Cathryn Vasseleu