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Now showing 1 - 10 of 12
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    Rendering Discrete Random Media Using Precomputed Scattering Solutions
    (The Eurographics Association, 2007) Moon, Jonathan T.; Walter, Bruce; Marschner, Stephen R.; Jan Kautz and Sumanta Pattanaik
    This 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.
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    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 Conti
    Immersive 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.
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    Eulerian Motion Blur
    (The Eurographics Association, 2007) Kim, Doyub; Ko, Hyeong-Seok; D. Ebert and S. Merillou
    This 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.
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    Developable Surfaces from Arbitrary Sketched Boundaries
    (The Eurographics Association, 2007) Rose, Kenneth; Sheffer, Alla; Wither, Jamie; Cani, Marie-Paule; Thibert, Boris; Alexander Belyaev and Michael Garland
    We present a method for extracting a hierarchical, rigid skeleton from a set of example poses. We then use this skeleton to not only reproduce the example poses, but create new deformations in the same style as the examples. Since rigid skeletons are used by most 3D modeling software, this skeleton and the corresponding vertex weights can be inserted directly into existing production pipelines. To create the skeleton, we first estimate the rigid transformations of the bones using a fast, face clustering approach. We present an efficient method for clustering by providing a Rigid Error Function that finds the best rigid transformation from a set of points in a robust, space efficient manner and supports fast clustering operations. Next, we solve for the vertex weights and enforce locality in the resulting weight distributions. Finally, we use these weights to determine the connectivity and joint locations of the skeleton.
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    Guided TimeWarping for Motion Editing
    (The Eurographics Association, 2007) Hsu, Eugene; Silva, Marco da; Popovic, Jovan; Dimitris Metaxas and Jovan Popovic
    Time warping allows users to modify timing without affecting poses. It has many applications in animation systems for motion editing, such as refining motions to meet new timing constraints or modifying the acting of animated characters. However, time warping typically requires many manual adjustments to achieve the desired results. We present a technique which simplifies this process by allowing time warps to be guided by a provided reference motion. Given few timing constraints, it computes a warp that both satisfies these constraints and maximizes local timing similarities to the reference. The algorithm is fast enough to incorporate into standard animation workflows. We apply the technique to two common tasks: preserving the natural timing of motions under new time constraints and modifying the timing of motions for stylistic effects.
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    Dirty Glass: Rendering Contamination on Transparent Surfaces
    (The Eurographics Association, 2007) Gu, Jinwei; Ramamoorthi, Ravi; Belhumeur, Peter; Nayar, Shree; Jan Kautz and Sumanta Pattanaik
    Rendering of clean transparent objects has been well studied in computer graphics. However, real-world transparent objects are seldom clean their surfaces have a variety of contaminants such as dust, dirt, and lipids. These contaminants produce a number of complex volumetric scattering effects that must be taken into account when creating photorealistic renderings. In this paper, we take a step toward modeling and rendering these effects. We make the assumption that the contaminant is an optically thin layer and construct an analytic model following results in radiative transport theory and computer graphics. Moreover, the spatial textures created by the different types of contamination are also important in achieving visual realism. To this end, we measure the spatially varying thicknesses and the scattering parameters of a number of glass panes with various types of dust, dirt, and lipids. We also develop a simple interactive synthesis tool to create novel instances of the measured contamination patterns. We show several results that demonstrate the use of our scattering model for rendering 3D scenes, as well as modifying real 2D photographs.
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    On the Beat! Timing and Tension for Dynamic Characters
    (The Eurographics Association, 2007) Allen, Brian; Chu, Derek; Shapiro, Ari; Faloutsos, Petros; Dimitris Metaxas and Jovan Popovic
    Dynamic simulation is a promising complement to kinematic motion synthesis, particularly in cases where simulated characters need to respond to unpredictable interactions. Moving beyond simple rag-doll effects, though, requires dynamic control. The main issue with dynamic control is that there are no standardized techniques that allow an animator to precisely specify the timing of the motion while still providing natural response to external disturbances. The few proposed techniques that address this problem are based on heuristically or manually tuning proportional-derivative (PD) control parameters and do not generalize easily. We propose an approach to dynamic character control that is able to honor timing constraints, to provide naturallooking motion and to allow for realistic response to perturbations. Our approach uses traditional PD control to interpolate between key-frames. The key innovation is that the parameters of the PD controllers are computed for each joint analytically. By continuously updating these parameters over time, the controller is able to respond naturally to both external perturbations and changes in the state of the character
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    Efficient Rendering of Human Skin
    (The Eurographics Association, 2007) d'Eon, Eugene; Luebke, David; Enderton, Eric; Jan Kautz and Sumanta Pattanaik
    Existing offline techniques for modeling subsurface scattering effects in multi-layered translucent materials such as human skin achieve remarkable realism, but require seconds or minutes to generate an image. We demonstrate rendering of multi-layer skin that achieves similar visual quality but runs orders of magnitude faster. We show that sums of Gaussians provide an accurate approximation of translucent layer diffusion profiles, and use this observation to build a novel skin rendering algorithm based on texture space diffusion and translucent shadow maps. Our technique requires a parameterized model but does not otherwise rely on any precomputed information, and thus extends trivially to animated or deforming models. We achieve about 30 frames per second for realistic real-time rendering of deformable human skin under dynamic lighting.
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    Example-Based Skeleton Extraction
    (The Eurographics Association, 2007) Schaefer, Scott; Yuksel, Can; Alexander Belyaev and Michael Garland
    We present a method for extracting a hierarchical, rigid skeleton from a set of example poses. We then use this skeleton to not only reproduce the example poses, but create new deformations in the same style as the examples. Since rigid skeletons are used by most 3D modeling software, this skeleton and the corresponding vertex weights can be inserted directly into existing production pipelines. To create the skeleton, we first estimate the rigid transformations of the bones using a fast, face clustering approach. We present an efficient method for clustering by providing a Rigid Error Function that finds the best rigid transformation from a set of points in a robust, space efficient manner and supports fast clustering operations. Next, we solve for the vertex weights and enforce locality in the resulting weight distributions. Finally, we use these weights to determine the connectivity and joint locations of the skeleton.
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    A Fast and Compact Solver for the Shallow Water Equations
    (The Eurographics Association, 2007) Lee, Richard; O'Sullivan, Carol; John Dingliana and Fabio Ganovelli
    This paper presents a fast and simple method for solving the shallow water equations. The water velocity and height variables are collocated on a uniform grid and a novel, unified scheme is used to advect all quantities together. Furthermore, we treat the fluid as weakly compressible to avoid solving a pressure Poisson equation. We sacrifice accuracy and unconditional stability for speed, but we show that our algorithm is sufficiently stable and fast enough for real-time applications.