40-Issue 4

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https://diglib.eg.org/handle/10.2312/2633074

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Browsing 40-Issue 4 by Subject "Computing methodologies"

Now showing 1 - 7 of 7
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    An Analytic BRDF for Materials with Spherical Lambertian Scatterers
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) d'Eon, Eugene; Bousseau, Adrien and McGuire, Morgan
    We present a new analytic BRDF for porous materials comprised of spherical Lambertian scatterers. The BRDF has a single parameter: the albedo of the Lambertian particles. The resulting appearance exhibits strong back scattering and saturation effects that height-field-based models such as Oren-Nayar cannot reproduce.
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    A Combined Scattering and Diffraction Model for Elliptical Hair Rendering
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Benamira, Alexis; Pattanaik, Sumanta; Bousseau, Adrien and McGuire, Morgan
    Realistic hair rendering relies on fiber scattering models. These models are based on either ray tracing or on full wavepropagation through the hair fiber. Ray tracing can model most of the scattering phenomenon observed but misses the important effect of diffraction. Indeed human natural hair specific dimensions and geometry demands for the wave nature of light to be taken into consideration for accurate rendering. However, current full-wave model requires nonpratical, several days precomputation, that needs to be repeated for every change in the hair geometry or color, for appropriate results. We present in this paper a dual hair scattering model which considers the dual aspect of light: as a wave and as a ray. Our model accurately simulates both diffraction and scattering phenomena without requiring any precomputation. Furthermore, it can simulate light transport in hairs of arbitrary elliptical cross-sections. This new dual approach enables our model to significantly improve the appearance of rendered hair and qualitatively match scattering and diffraction effects seen in photos of real hair while adding little computation overhead.
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    Deep Portrait Lighting Enhancement with 3D Guidance
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Han, Fangzhou; Wang, Can; Du, Hao; Liao, Jing; Bousseau, Adrien and McGuire, Morgan
    Despite recent breakthroughs in deep learning methods for image lighting enhancement, they are inferior when applied to portraits because 3D facial information is ignored in their models. To address this, we present a novel deep learning framework for portrait lighting enhancement based on 3D facial guidance. Our framework consists of two stages. In the first stage, corrected lighting parameters are predicted by a network from the input bad lighting image, with the assistance of a 3D morphable model and a differentiable renderer. Given the predicted lighting parameter, the differentiable renderer renders a face image with corrected shading and texture, which serves as the 3D guidance for learning image lighting enhancement in the second stage. To better exploit the long-range correlations between the input and the guidance, in the second stage, we design an imageto- image translation network with a novel transformer architecture, which automatically produces a lighting-enhanced result. Experimental results on the FFHQ dataset and in-the-wild images show that the proposed method outperforms state-of-the-art methods in terms of both quantitative metrics and visual quality.
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    Moving Basis Decomposition for Precomputed Light Transport
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Silvennoinen, Ari; Sloan, Peter-Pike; Bousseau, Adrien and McGuire, Morgan
    We study the problem of efficient representation of potentially high-dimensional, spatially coherent signals in the context of precomputed light transport. We present a basis decomposition framework, Moving Basis Decomposition (MBD), that generalizes many existing basis expansion methods and enables high-performance, seamless reconstruction of compressed data. We develop an algorithm for solving large-scale MBD problems. We evaluate MBD against state-of-the-art in a series of controlled experiments and describe a real-world application, where MBD serves as the backbone of a scalable global illumination system powering multiple, current and upcoming 60Hz AAA-titles running on a wide range of hardware platforms.
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    Optimised Path Space Regularisation
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Weier, Philippe; Droske, Marc; Hanika, Johannes; Weidlich, Andrea; Vorba, Jirí; Bousseau, Adrien and McGuire, Morgan
    We present Optimised Path Space Regularisation (OPSR), a novel regularisation technique for forward path tracing algorithms. Our regularisation controls the amount of roughness added to materials depending on the type of sampled paths and trades a small error in the estimator for a drastic reduction of variance in difficult paths, including indirectly visible caustics. We formulate the problem as a joint bias-variance minimisation problem and use differentiable rendering to optimise our model. The learnt parameters generalise to a large variety of scenes irrespective of their geometric complexity. The regularisation added to the underlying light transport algorithm naturally allows us to handle the problem of near-specular and glossy path chains robustly. Our method consistently improves the convergence of path tracing estimators, including state-of-the-art path guiding techniques where it enables finding otherwise hard-to-sample paths and thus, in turn, can significantly speed up the learning of guiding distributions.
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    PosterChild: Blend-Aware Artistic Posterization
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Chao, Cheng-Kang; Singh, Karan; Gingold, Yotam; Bousseau, Adrien and McGuire, Morgan
    Posterization is an artistic effect which converts continuous images into regions of constant color with smooth boundaries, often with an artistically recolored palette. Artistic posterization is extremely time-consuming and tedious. We introduce a blend-aware algorithm for generating posterized images with palette-based control for artistic recoloring. Our algorithm automatically extracts a palette and then uses multi-label optimization to find blended-color regions in terms of that palette. We smooth boundaries away from image details with frequency-guided median filtering. We evaluate our algorithm with a comparative user study and showcase its ability to produce compelling posterizations of a variety of inputs. Our parameters provide artistic control and enable cohesive, real-time recoloring after posterization pre-processing.
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    Rendering Point Clouds with Compute Shaders and Vertex Order Optimization
    (The Eurographics Association and John Wiley & Sons Ltd., 2021) Schütz, Markus; Kerbl, Bernhard; Wimmer, Michael; Bousseau, Adrien and McGuire, Morgan
    In this paper, we present several compute-based point cloud rendering approaches that outperform the hardware pipeline by up to an order of magnitude and achieve significantly better frame times than previous compute-based methods. Beyond basic closest-point rendering, we also introduce a fast, high-quality variant to reduce aliasing. We present and evaluate several variants of our proposed methods with different flavors of optimization, in order to ensure their applicability and achieve optimal performance on a range of platforms and architectures with varying support for novel GPU hardware features. During our experiments, the observed peak performance was reached rendering 796 million points (12.7GB) at rates of 62 to 64 frames per second (50 billion points per second, 802GB/s) on an RTX 3090 without the use of level-of-detail structures. We further introduce an optimized vertex order for point clouds to boost the efficiency of GL_POINTS by a factor of 5x in cases where hardware rendering is compulsory. We compare different orderings and show that Morton sorted buffers are faster for some viewpoints, while shuffled vertex buffers are faster in others. In contrast, combining both approaches by first sorting according to Morton-code and shuffling the resulting sequence in batches of 128 points leads to a vertex buffer layout with high rendering performance and low sensitivity to viewpoint changes.