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Item A Multifragment Renderer for Material Aging Visualization(The Eurographics Association, 2018) Adamopoulos, Georgios; Moutafidou, Anastasia; Drosou, Anastasios; Tzovaras, Dimitrios; Fudos, Ioannis; Jain, Eakta and Kosinka, JiríPeople involved in curatorial work and in preservation/conservation tasks need to understand exactly the nature of aging and to prevent it with minimal preservation work. In this scenario, it is of extreme importance to have tools to produce and visualize digital representations and models of visual surface appearance and material properties, to help the scientist understand how they evolve over time and under particular environmental conditions. We report on the development of a multifragment renderer for visualizing and combining the results of simulated aging of artwork objects. Several natural aging processes manifest themselves through change of color, fading, deformations or cracks. Furthermore, changes in the materials underneath the visible layers may be detected or simulated.Item Smooth Blended Subdivision Shading(The Eurographics Association, 2018) Bakker, Jelle; Barendrecht, Pieter J.; Kosinka, Jiri; Diamanti, Olga and Vaxman, AmirThe concept known as subdivision shading aims at improving the shading of subdivision surfaces. It is based on the subdivision of normal vectors associated with the control net of the surface. By either using the resulting subdivided normal field directly, or blending it with the normal field of the limit surface, renderings of higher visual smoothness can be obtained. In this work we propose a different and more versatile approach to blend the two normal fields, yielding not only better results, but also a proof that our blended normal field is C1.Item Physically-based Rendering of Highly Scattering Fluorescent Solutions using Path Tracing(The Eurographics Association, 2016) Abdellah, Marwan; Bilgili, Ahmet; Eilemann, Stefan; Markram, Henry; Schürmann, Felix; Luis Gonzaga Magalhaes and Rafal MantiukWe introduce a physically-plausible Monte Carlo rendering technique that is capable of treating highly scattering participating media in the presence of fluorescent mixtures. Our model accounts for the actual intrinsic spectroscopic characteristics of fluorescent dyes. The model leads to an estimator for simulating the light interaction with highly scattering fluorescent-tagged participating media. Our system is applied to render images of two fluorescent solutions under different conditions. The model is qualitatively analyzed and validated against experimental emission spectra of fluorescent dyes.Item A Computational Model of Light-Sheet Fluorescence Microscopy using Physically-based Rendering(The Eurographics Association, 2015) Abdellah, Marwan; Bilgili, Ahmet; Eilemann, Stefan; Markram, Henry; Schürmann, Felix; B. Solenthaler and E. PuppoWe present a physically-based computational model of the light sheet fluorescence microscope (LSFM). Based on Monte Carlo ray tracing and geometric optics, our method simulates the operational aspects and image formation process of the LSFM. An extension for previous fluorescence models is developed to account for the intrinsic characteristics of fluorescent dyes in order to accurately simulate light interaction with fluorescent-tagged biological specimen. This extension was quantitatively validated against the fluorescence brightness equation and experimental spectra of different dyes. We demonstrate first results of our rendering pipeline to a simplified brain tissue model reconstructed from the somatosensory cortex of a young rat.Item A Comparison of GPU Tessellation Strategies for Multisided Patches(The Eurographics Association, 2018) Hettinga, Gerben Jan; Barendrecht, Pieter J.; Kosinka, Jiri; Diamanti, Olga and Vaxman, AmirWe propose an augmentation of the traditional tessellation pipeline with several different strategies that efficiently render multisided patches using generalised barycentric coordinates. The strategies involve different subdivision steps and the usage of textures. In addition, we show that adaptive tessellation techniques naturally extend to some of these strategies whereas others need a slight adjustment. The technique of Loop et al. [LSNC09], commonly known as ACC-2, is extended to multisided faces to illustrate the effectiveness of multisided techniques. A performance and quality comparison is made between the different strategies and remarks on the techniques and implementation details are provided.Item Monte Carlo Methods for Volumetric Light Transport Simulation(The Eurographics Association and John Wiley & Sons Ltd., 2018) Novák, Jan; Georgiev, Iliyan; Hanika, Johannes; Jarosz, Wojciech; Hildebrandt, Klaus and Theobalt, ChristianThe wide adoption of path-tracing algorithms in high-end realistic rendering has stimulated many diverse research initiatives. In this paper we present a coherent survey of methods that utilize Monte Carlo integration for estimating light transport in scenes containing participating media. Our work complements the volume-rendering state-of-the-art report by Cerezo et al. [CPP 05]; we review publications accumulated since its publication over a decade ago, and include earlier methods that are key for building light transport paths in a stochastic manner. We begin by describing analog and non-analog procedures for freepath sampling and discuss various expected-value, collision, and track-length estimators for computing transmittance. We then review the various rendering algorithms that employ these as building blocks for path sampling. Special attention is devoted to null-collision methods that utilize fictitious matter to handle spatially varying densities; we import two ''next-flight'' estimators originally developed in nuclear sciences. Whenever possible, we draw connections between image-synthesis techniques and methods from particle physics and neutron transport to provide the reader with a broader context.Item Accelerating Sphere Tracing(The Eurographics Association, 2018) Bálint, Csaba; Valasek, Gábor; Diamanti, Olga and Vaxman, AmirThis paper presents two performance improvements on sphere tracing. First, a sphere tracing variant designed to take optimal step sizes near planar surfaces is proposed. We demonstrate how relaxation is used to make this method applicable to sphere tracing arbitrary geometries and compare its performance to classical (by Hart) and relaxed (Keinert et al.) sphere tracing in rendering various scenes. The method is also general in the sense that it can be applied in any scenario that requires the computation of ray-surface intersections. Our second contribution is a multi-resolution rendering strategy that can be used with any sphere tracing variant. By starting from a lower resolution and gradually increasing it, render times can be reduced.