Browsing by Author "Jarabo, Adrian"

Now showing 1 - 6 of 6
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    Accelerating Hair Rendering by Learning High-Order Scattered Radiance
    (The Eurographics Association and John Wiley & Sons Ltd., 2023) KT, Aakash; Jarabo, Adrian; Aliaga, Carlos; Chiang, Matt Jen-Yuan; Maury, Olivier; Hery, Christophe; Narayanan, P. J.; Nam, Giljoo; Ritschel, Tobias; Weidlich, Andrea
    Efficiently and accurately rendering hair accounting for multiple scattering is a challenging open problem. Path tracing in hair takes long to converge while other techniques are either too approximate while still being computationally expensive or make assumptions about the scene. We present a technique to infer the higher order scattering in hair in constant time within the path tracing framework, while achieving better computational efficiency. Our method makes no assumptions about the scene and provides control over the renderer's bias & speedup. We achieve this by training a small multilayer perceptron (MLP) to learn the higher-order radiance online, while rendering progresses. We describe how to robustly train this network and thoroughly analyze our resulting renderer's characteristics. We evaluate our method on various hairstyles and lighting conditions. We also compare our method against a recent learning based & a traditional real-time hair rendering method and demonstrate better quantitative & qualitative results. Our method achieves a significant improvement in speed with respect to path tracing, achieving a run-time reduction of 40%-70% while only introducing a small amount of bias.
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    Bidirectional Rendering of Vector Light Transport
    (© 2018 The Eurographics Association and John Wiley & Sons Ltd., 2018) Jarabo, Adrian; Arellano, Victor; Chen, Min and Benes, Bedrich
    On the foundations of many rendering algorithms it is the symmetry between the path traversed by light and its adjoint path starting from the camera. However, several effects, including polarization or fluorescence, break that symmetry, and are defined only on the direction of light propagation. This reduces the applicability of bidirectional methods that exploit this symmetry for simulating effectively light transport. In this work, we focus on how to include these non‐symmetric effects within a bidirectional rendering algorithm. We generalize the path integral to support the constraints imposed by non‐symmetric light transport. Based on this theoretical framework, we propose modifications on two bidirectional methods, namely bidirectional path tracing and photon mapping, extending them to support polarization and fluorescence, in both steady and transient state. On the foundations of many rendering algorithms, it is the symmetry between the path traversed by light and its adjoint path starting from the camera. However, several effects, including polarization or fluorescence, break that symmetry, and are defined only on the direction of light. This reduces the applicability of bidirectional methods that exploit this symmetry for simulating effectively light transport. In this work, we focus on how to include these non‐symmetric effects within a bidirectional rendering algorithm.
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    A Biologically-Inspired Appearance Model for Snake Skin
    (The Eurographics Association, 2023) Padron-Griffe, Juan Raul; Bielsa, Diego; Jarabo, Adrian; Muñoz, Adolfo; Gimeno Sancho, Jesús; Comino Trinidad, Marc
    Simulating the light transport on biological tissues is a longstanding challenge, given its complex multilayered structure. In biology, one of the most remarkable and studied examples of tissues are the scales that cover the skin of reptiles, which present a combination of photonic structures and pigmentation. This is, however, a somewhat ignored problem in computer graphics. In this work, we propose a multilayered appearance model based on the anatomy of the snake skin. Some snakes are known for their striking, highly iridescent scales resulting from light interference. We model snake skin as a two-layered reflectance function: The top layer is a thin layer resulting on a specular iridescent reflection, while the bottom layer is a diffuse highlyabsorbing layer, that results into a dark diffuse appearance that maximizes the iridescent color of the skin. We demonstrate our layered material on a wide range of appearances, and show that our model is able to qualitatively match the appearance of snake skin.
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    Efficient Propagation of Light Field Edits
    (The Eurographics Association, 2021) Jarabo, Adrian; Masia, Belen; Gutierrez, Diego; Silva, F. and Gutierrez, D. and Rodríguez, J. and Figueiredo, M.
    Light field editing is a complex task, due to the large amount of data and the need to keep consistency between views. This has hampered the creation of efficient edit propagation methods, similar to those existing for single images. We propose a framework to edit light fields at interactive rates, by propagating some sparse user edits in the full light field. This propagation is guided by a novel affinity function, which forces similar pixels (defined by our affinity space) to receive similar edits, thus ensuring consistency. To manage the light field's large amount of data, we propose a novel multi-dimensional downsampling technique: we first cluster pixels with high affinity, and then perform edit propagation over the downsampled data. We finally upsample back to the original full resolution, maintaining visual fidelity and view consistency between views.
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    A Hyperspectral Space of Skin Tones for Inverse Rendering of Biophysical Skin Properties
    (The Eurographics Association and John Wiley & Sons Ltd., 2023) Aliaga, Carlos; Xia, Mengqi; Xie, Hao; Jarabo, Adrian; Braun, Gustav; Hery, Christophe; Ritschel, Tobias; Weidlich, Andrea
    We present a method for estimating the main properties of human skin, leveraging a hyperspectral dataset of skin tones synthetically generated through a biophysical layered skin model and Monte Carlo light transport simulations. Our approach learns the mapping between the skin parameters and diffuse skin reflectance in such space through an encoder-decoder network. We assess the performance of RGB and spectral reflectance up to 1 µm, allowing the model to retrieve visible and near-infrared. Instead of restricting the parameters to values in the ranges reported in medical literature, we allow the model to exceed such ranges to gain expressiveness to recover outliers like beard, eyebrows, rushes and other imperfections. The continuity of our albedo space allows to recover smooth textures of skin properties, enabling reflectance manipulations by meaningful edits of the skin properties. The space is robust under different illumination conditions, and presents high spectral similarity with the current largest datasets of spectral measurements of real human skin while expanding its gamut.
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    Progressive Transient Photon Beams
    (© 2019 Eurographics ‐ The European Association for Computer Graphics and John Wiley & Sons Ltd, 2019) Marco, Julio; Guillén, Ibón; Jarosz, Wojciech; Gutierrez, Diego; Jarabo, Adrian; Chen, Min and Benes, Bedrich
    In this work, we introduce a novel algorithm for transient rendering in participating media. Our method is consistent, robust and is able to generate animations of time‐resolved light transport featuring complex caustic light paths in media. We base our method on the observation that the spatial continuity provides an increased coverage of the temporal domain, and generalize photon beams to transient‐state. We extend stead‐state photon beam radiance estimates to include the temporal domain. Then, we develop a progressive variant of our approach which provably converges to the correct solution using finite memory by averaging independent realizations of the estimates with progressively reduced kernel bandwidths. We derive the optimal convergence rates accounting for space and time kernels, and demonstrate our method against previous consistent transient rendering methods for participating media.In this work, we introduce a novel algorithm for transient rendering in participating media. Our method is consistent, robust and is able to generate animations of time‐resolved light transport featuring complex caustic light paths in media. We base our method on the observation that the spatial continuity provides an increased coverage of the temporal domain, and generalize photon beams to transient‐state. We extend stead‐state photon beam radiance estimates to include the temporal domain. Then, we develop a progressive variant of our approach which provably converges to the correct solution using finite memory by averaging independent realizations of the estimates with progressively reduced kernel bandwidths. We derive the optimal convergence rates accounting for space and time kernels, and demonstrate our method against previous consistent transient rendering methods for participating media.