MAM2017: Eurographics Workshop on Material Appearance Modeling

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https://diglib.eg.org/handle/10.2312/2631738

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Browsing MAM2017: Eurographics Workshop on Material Appearance Modeling by Subject "shadowing"

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    Appearance of Interfaced Lambertian Microfacets, using STD Distribution
    (The Eurographics Association, 2017) Ribardière, M.; Meneveaux, D.; Bringier, B.; Simonot, L.; Reinhard Klein and Holly Rushmeier
    This paper presents the use of Student’s T-Distribution (STD) with interfaced Lambertian (IL) microfacets. The resulting model increases the range of materials while providing a very accurate adjustment of appearance. STD has been recently proposed as a generalized distribution of microfacets which includes Beckmann and GGX widely used in computer graphics; IL corresponds to a physical representation of a Lambertian substrate covered with a flat Fresnel interface. We illustrate the appearance variations that can be observed, and discuss the advantages of using such a combination.
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    Experimental Analysis of BSDF Models
    (The Eurographics Association, 2017) Kurt, Murat; Reinhard Klein and Holly Rushmeier
    The Bidirectional Scattering Distribution Function (BSDF) describes the appearance of an optically thin, translucent material by its interaction with light at a surface point. Various BSDF models have been proposed to represent BSDFs. In this paper, we experimentally analyze a few of BSDF models in terms of their accuracy to represent measured BSDFs, their required storage sizes and computation times. To make a fair comparison of BSDF models, we measured three samples of optically thin, translucent materials (hunter douglas, orange glass, structured glass) by using pgII gonio-photometer. Based on rendered images, required storage sizes and computation times, we compare the performance of the BSDF models. We show that datadriven BSDF models give a more accurate representation of measured BSDFs, while data-driven BSDF models require much more storage sizes and computation times.We also show that BSDF measurements from highly anisotropic translucent materials can not be expressed by an analytical BSDF model visually correctly.
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    Image-based Remapping of Material Appearance
    (The Eurographics Association, 2017) Sztrajman, Alejandro; Krivánek, Jaroslav; Wilkie, Alexander; Weyrich, Tim; Reinhard Klein and Holly Rushmeier
    Digital 3D content creation requires the ability to exchange assets across multiple software applications. For many 3D asset types, standard formats and interchange conventions are available. For material definitions, however, inter-application exchange is still hampered by different software packages supporting different BRDF models. To make matters worse, even if nominally identical BRDF models are supported, these often differ in their implementation, due to optimisations and safeguards in individual renderers. To facilitate appearance-preserving translation between different BRDF models whose precise implementation is not known (arguably the standard case with commercial systems), we propose a robust translation scheme which leaves BRDF evaluation to the targeted rendering system, and which expresses BRDF similarity in image space. As we will show, even naïve applications of a nonlinear fit which uses such an image space residual metric work well in some cases; however, it does suffer from instabilities for certain material parameters. We propose strategies to mitigate these instabilities and perform reliable parameter remappings between differing BRDF definitions. We report on experiences with this remapping scheme, both with respect to robustness and visual differences of the fits.