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Item Illustrative Context-Preserving Volume Rendering(The Eurographics Association, 2005) Bruckner, Stefan; Grimm, Sören; Kanitsar, Armin; Gröller, M. Eduard; Ken Brodlie and David Duke and Ken JoyIn volume rendering it is very difficult to simultaneously visualize interior and exterior structures while preserving clear shape cues. Very transparent transfer functions produce cluttered images with many overlapping structures, while clipping techniques completely remove possibly important context information. In this paper we present a new model for volume rendering, inspired by techniques from illustration that provides a means of interactively inspecting the interior of a volumetric data set in a feature-driven way which retains context information. The context-preserving volume rendering model uses a function of shading intensity, gradient magnitude, distance to the eye point, and previously accumulated opacity to selectively reduce the opacity in less important data regions. It is controlled by two user-specified parameters. This new method represents an alternative to conventional clipping techniques, shares their easy and intuitive user control, but does not suffer from the drawback of missing context information.Item Realistic Water Volumes in Real-Time(The Eurographics Association, 2006) Baboud, Lionel; Décoret, Xavier; Norishige Chiba and Eric GalinWe present a real-time technique to render realistic water volumes. Water volumes are represented as the space enclosed between a ground heightfield and an animable water surface heightfield. This representation allows the application of recent GPU-based heightfield rendering algorithms. Our method is a simplified raytracing approach which correctly handles reflections and refractions and allows us to render complex effects such as light absorption, refracted shadows and refracted caustics. It runs at high framerates by exploiting the power of the latest graphic cards, and could be used in real-time applications like video games, or interactive simulation.Item Polynomial Approximation of Blinn-Phong Model(The Eurographics Association, 2006) Öztürk, Aydin; Bilgili, Ahmet; Kurt, Murat; Louise M. Lever and Mary McDerbyThe Phong model has been one of the oldest and the most popular reflection models in Computer Graphics. It can be used to model specular highlights of various materials. In this paper, we consider a polynomial model and obtain a linear approximation of the Blinn-Phong model. Approximation errors were obtained for the proposed model and empirical comparisons were made using a measured BRDF data set. Based on the empirical results, it is shown that proposed model provides visually convincing representation of BRDF and performs well for modeling the surface reflectance.Item Statistical Acquisition of Texture Appearance(The Eurographics Association, 2006) Ngan, Addy; Durand, Frédo; Tomas Akenine-Moeller and Wolfgang HeidrichWe propose a simple method to acquire and reconstruct material appearance with sparsely sampled data. Our technique renders elaborate view- and light-dependent effects and faithfully reproduces materials such as fabrics and knitwears. Our approach uses sparse measurements to reconstruct a full six-dimensional Bidirectional Texture Function (BTF). Our reconstruction only require input images from the top view to be registered, which is easy to achieve with a fixed camera setup. Bidirectional properties are acquired from a sparse set of viewing directions through image statistics and therefore precise registrations for these views are unnecessary. Our technique is based on multi-scale histograms of image pyramids. The full BTF is generated by matching the corresponding pyramid histograms to interpolated top-view images.We show that the use of multi-scale image statistics achieves a visually plausible appearance. However, our technique does not fully capture sharp specularities or the geometric aspects of parallax. Nonetheless, a large class of materials can be reproduced well with our technique, and our statistical characterization enables acquisition of such materials efficiently using a simple setup.Item Rendering Discrete Random Media Using Precomputed Scattering Solutions(The Eurographics Association, 2007) Moon, Jonathan T.; Walter, Bruce; Marschner, Stephen R.; Jan Kautz and Sumanta PattanaikThis paper addresses light transport through a discrete random medium, which we define as a volume filled with macroscopic scattering geometry generated by a random process. This formulation is more general than standard radiative transport, because it can be applied to media that are made up of closely packed scatterers. A new approach to rendering these media is introduced, based on precomputed solutions to a local multiple scattering problem, including a new algorithm for generating paths through random media that moves through the interior of the medium in large strides without considering individual scattering events. A method for rendering homogeneous isotropic random media is described that generates paths using precomputed scattering solutions compressed and randomly sampled using Nonnegative Matrix Factorization. It can efficiently render discrete media, such as a large pile of glass objects, in which the individual scatterers are visible. The method is demonstrated on scenes containing tens of thousands of transparent, specular objects that are nearly impossible to render with standard global illumination techniques.Item Perception-based Lighting Design(The Eurographics Association, 2006) Ha, Hai Nam; Olivier, Patrick; Louise M. Lever and Mary McDerbyPerception-based lighting design approaches model image quality using a cognitively grounded objective function which is in turn optimised through manipulation of the lighting parameters of a scene. We present, and demonstrate, a detailed implementation of perception-based lighting design, including the application and evaluation of stochastic optimisation using genetic algorithms.Item Perceived Rendering Thresholds for High-Fidelity Graphics on Small Screen Devices(The Eurographics Association, 2006) Aranha, M.; Debattista, K.; Chalmers, A.; Hill, S.; Louise M. Lever and Mary McDerbySmall screen devices, also known as small-form-factor (SFF) devices including mobile phones and ultra mobile PCs are increasingly ubiquitous. Their uses includes gaming, navigation and interactive visualisation. SFF devices are, however, inherently limited by their physical characteristics for perception as well as limited processing and battery power. High-fidelity graphic systems have significant computational requirements which can be reduced through use of perceptually-based rendering techniques. In order to exploit these techniques on SFF devices a sound understanding of the perceptual characteristics of the display device is needed. This paper investigates the perceived rendering threshold specific for SFF devices in comparison to traditional display devices. We show that the threshold for SFF systems differs significantly from typical displays indicating substantial savings in rendering quality and thus computational resources can be achieved for SFF devices.Item Real Positioning in Virtual Environments Using Game Engines(The Eurographics Association, 2007) Chiara, Rosario De; Santo, Valentina Di; Erra, Ugo; Scarano, Vittorio; Raffaele De Amicis and Giuseppe ContiImmersive virtual environments offer a natural setting for educational and instructive experiences for users, and game engine technology offers an interesting, cost-effective and efficient solution for building them. In this paper we describe an ongoing project whose goal is to provide a virtual environment where the real location of the user is used to position the user's avatar into the virtual environment.Item Eulerian Motion Blur(The Eurographics Association, 2007) Kim, Doyub; Ko, Hyeong-Seok; D. Ebert and S. MerillouThis paper describes a motion blur technique which can be applied to rendering fluid simulations that are carried out in the Eulerian framework. Existing motion blur techniques can be applied to rigid bodies, deformable solids, clothes, and several other kinds of objects, and produce satisfactory results. As there is no specific reason to discriminate fluids from the above objects, one may consider applying an existing motion blur technique to render fluids. However, here we show that existing motion blur techniques are intended for simulations carried out in the Lagrangian framework, and are not suited to Eulerian simulations. Then, we propose a new motion blur technique that is suitable for rendering Eulerian simulations.Item Simulating Caustics due to Liquid-Solid Interface Menisci(The Eurographics Association, 2006) Bourque, Eric; Dufort, Jean-François; Laprade, Michelle; Poulin, Pierre; Norishige Chiba and Eric GalinA solid partially immersed in a liquid creates a local deformation of the liquid surface at their interface. This deformation, called a meniscus, exhibits high curvature, and as such, produces very intriguing caustic patterns. However, this natural phenomena has been neglected in almost all previous liquid simulation techniques. We propose a complete solution to model and render meniscal illumination effects. First, we outline a physicallymotivated approach to approximating the geometry of the meniscus. We then describe the targeted photon map, an adapted photon map which facilitates efficient sampling of the finely tessellated menisci. This technique, which integrates well within traditional photon mapping, allows for automatically rendering illumination effects for complex solid-liquid interfaces. Several images rendered using this technique are presented and are compared to their real-world counterparts.