EG2010

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https://diglib.eg.org/handle/10.2312/277

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gProximity: Hierarchical GPU-based Operations for Collision and Distance Queries
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Lauterbach, C.; Mo, Q.; Manocha, D.
We present novel parallel algorithms for collision detection and separation distance computation for rigid and deformable models that exploit the computational capabilities of many-core GPUs. Our approach uses thread and data parallelism to perform fast hierarchy construction, updating, and traversal using tight-fitting bounding volumes such as oriented bounding boxes (OBB) and rectangular swept spheres (RSS). We also describe efficient algorithms to compute a linear bounding volume hierarchy (LBVH) and update them using refitting methods. Moreover, we show that tight-fitting bounding volume hierarchies offer improved performance on GPU-like throughput architectures. We use our algorithms to perform discrete and continuous collision detection including self-collisions, as well as separation distance computation between non-overlapping models. In practice, our approach (gProximity) can perform these queries in a few milliseconds on a PC with NVIDIA GTX 285 card on models composed of tens or hundreds of thousands of triangles used in cloth simulation, surgical simulation, virtual prototyping and N-body simulation. Moreover, we observe more than an order of magnitude performance improvement over prior GPU-based algorithms.
Uniview - Visualizing the Universe
(The Eurographics Association, 2010) Klashed, Staffan; Hemingsson, Per; Emmart, Carter; Cooper, Matthew; Ynnerman, Anders; Matthew Cooper and Kari Pulli
This paper describes the development of the software system, Uniview, the motivation behind some of the most prominent features of the system and the strengths and challenges of running a development project in such close collaboration with the users. Uniview is a sophisticated system for the visual display and exploration of the enormous and complex data which the human race has gathered about the universe. This beautiful, fascinating data, with it s sheer size both in terms of data elements and the distances between the objects in the known universe, presents challenges to the developer at all levels: from basic rendering through representation and to data managment.
Continuum Traffic Simulation
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Sewall, J.; Wilkie, D.; Merrell, P.; Lin, M. C.
We present a novel method for the synthesis and animation of realistic traffic flows on large-scale road networks. Our technique is based on a continuum model of traffic flow we extend to correctly handle lane changes and merges, as well as traffic behaviors due to changes in speed limit. We demonstrate how our method can be applied to the animation of many vehicles in a large-scale traffic network at interactive rates and show that our method can simulate believable traffic flows on publicly-available, real-world road data. We furthermore demonstrate the scalability of this technique on many-core systems.
Hybrid Simulation of Miscible Mixing with Viscous Fingering
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Shin, Seung-Ho; Kam, Hyeong Ryeol; Kim, Chang-Hun
By modeling mass transfer phenomena, we simulate solids and liquids dissolving or changing to other substances. We also deal with the very small-scale phenomena that occur when a fluid spreads out at the interface of another fluid. We model the pressure at the interfaces between fluids with Darcy s Law and represent the viscous fingering phenomenon in which a fluid interface spreads out with a fractal-like shape. We use hybrid grid-based simulation and smoothed particle hydrodynamics (SPH) to simulate intermolecular diffusion and attraction using particles at a computable scale. We have produced animations showing fluids mixing and objects dissolving.
No More Reinventing the Virtual Wheel: Middleware for Use in Computer Games and Interactive Computer Graphics Education
(The Eurographics Association, 2010) Anderson, Eike Falk; Peters, Christopher E.; L. Kjelldahl and G. Baronoski
The creation of application frameworks for teaching computer graphics has always been a time-consuming task, alleviated by the use of graphics API s that allow students more scope in investigating and creating graphics programs. A boom in Open Source software and the increasing growth of the game middleware industry has created a huge number of alternatives to choose from. Despite the adoption of such API s for teaching and experimentation, centralised sources of information regarding components are not commonplace; the process for gathering information about components may be cumbersome and is often left to chance. Here, we provide details of accessible middleware of relevance to the teaching of computer games and graphics curricula. Additionally, we describe concerns and considerations when introducing the use of middleware into a curriculum.
Using VisTrails and Provenance for Teaching Scientific Visualization
(The Eurographics Association, 2010) Silva, Cláudio T.; Anderson, Erik; Santos, Emanuele; Freire, Juliana; L. Kjelldahl and G. Baronoski
Over the last 20 years, visualization courses have been developed and offered at universities around the world. Many of these courses use established visualization libraries and tools (e.g., VTK, ParaView, AVS, VisIt) as a way to provide students a hands-on experience, allowing them to prototype and explore different visualization techniques. In this paper, we describe our experiences using VisTrails as a platform to teach scientific visualization. VisTrails is an open-source system that was designed to support exploratory computational tasks such as visualization and data analysis. Unlike previous scientific workflow and visualization systems, VisTrails provides a comprehensive provenance management infrastructure. We discuss how different features of the system, and in particular, the provenance information have changed the dynamics of the Scientific Visualization course we offer at the University of Utah. We also describe our initial attempts at using the provenance information to better assess our teaching techniques and student performance.
Digitizing Data: Computational Thinking for Middle School Students through Computer Graphics
(The Eurographics Association, 2010) Cutler, Robb; Hutton, Michelle; L. Kjelldahl and G. Baronoski
The concept of digitized data is fundamental to computer science, yet for many students, there is a disconnect between objects they encounter outside the computer and the data they interact with in the computer. A programmingbased approach can exacerbate the problem for young students who are developmentally unready for the abstraction required to translate the world into objects described through the syntax of a programming language. This case study describes the creation of a curricular unit called Digitizing Data, delivered in an eighth grade all-girls computer science class. The unit extends the CS Unplugged Image Representation lesson into a series of coordinated projects, culminating in students using a custom-built application to visualize three-dimensional objects and spaces. The project successfully engaged students in computational thinking, communicated a fundamental computer science topic without the barriers of programming, and allowed them to express computer science concepts creatively.
A Method for Fast Initialization of Markerless Object Tracking
(The Eurographics Association, 2010) Maiero, Jens; Hinkenjann, Andre; Anders Hast and Ivan Viola
In Mixed Reality (MR) Environments, the user s view is augmented with virtual, artificial objects. To visualize virtual objects, the position and orientation of the user s view or the camera is needed. Tracking of the user s viewpoint is an essential area in MR applications, especially for interaction and navigation. In present systems, the initialization is often complex. For this reason, we introduce a new method for fast initialization of markerless object tracking. This method is based on Speed Up Robust Features and paradoxically on a traditional markerbased library. Most markerless tracking algorithms can be divided into two parts: an offline and an online stage. The focus of this paper is optimization of the offline stage, which is often time-consuming.
A curvature based lightning model for quasi-global diffuse illumination
(The Eurographics Association, 2010) Seipel, S.; Liu, F.; Ericsson, M.; Anders Hast and Ivan Viola
In this paper we present extensions to local illumination models that take into account light transport and shadowmasking effects in the neighborhood of the surface point under evaluation. Central to our approach is the idea that local curvature represents geometric features in the surrounding neighborhood of this point which have an attenuating or enhancing effect regarding the diffuse illumination of this point. We introduce a lighting model that controls the amount of locally scattered light from the neighborhood based on a local curvature metric. The properties we aim at modeling with this curvature-based illumination model can be found in highly diffuse reflecting materials such as for example snow.
A Data-driven Segmentation for the Shoulder Complex
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Hong, Q Youn; Park, Sang Il; Hodgins, Jessica K.
The human shoulder complex is perhaps the most complicated joint in the human body being comprised of a set of three bones, muscles, tendons, and ligaments. Despite this anatomical complexity, computer graphics models for motion capture most often represent this joint as a simple ball and socket. In this paper, we present a method to determine a shoulder skeletal model that, when combined with standard skinning algorithms, generates a more visually pleasing animation that is a closer approximation to the actual skin deformations of the human body. We use a data-driven approach and collect ground truth skin deformation data with an optical motion capture system with a large number of markers (200 markers on the shoulder complex alone). We cluster these markers during movement sequences and discover that adding one extra joint around the shoulder improves the resulting animation qualitatively and quantitatively yielding a marker set of approximately 70 markers for the complete skeleton. We demonstrate the effectiveness of our skeletal model by comparing it with ground truth data as well as with recorded video. We show its practicality by integrating it with the conventional rendering/animation pipeline.
Real-time Realistic Ocean Lighting using Seamless Transitions from Geometry to BRDF
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Bruneton, Eric; Neyret, Fabrice; Holzschuch, Nicolas
Realistic animation and rendering of the ocean is an important aspect for simulators, movies and video games. By nature, the ocean is a difficult problem for Computer Graphics: it is a dynamic system, it combines wave trains at all scales, ranging from kilometric to millimetric. Worse, the ocean is usually viewed at several distances, from very close to the viewpoint to the horizon, increasing the multi-scale issue, and resulting in aliasing problems. The illumination comes from natural light sources (the Sun and the sky dome), is also dynamic, and often underlines the aliasing issues. In this paper, we present a new algorithm for modelling, animation, illumination and rendering of the ocean, in real-time, at all scales and for all viewing distances. Our algorithm is based on a hierarchical representation, combining geometry, normals and BRDF. For each viewing distance, we compute a simplified version of the geometry, and encode the missing details into the normal and the BRDF, depending on the level of detail required. We then use this hierarchical representation for illumination and rendering. Our algorithm runs in real-time, and produces highly realistic pictures and animations.
Data-parallel Micropolygon Rasterization
(The Eurographics Association, 2010) Eisenacher, Christian; Loop, Charles; H. P. A. Lensch and S. Seipel
Abstract We implement a tile based sort-middle rasterizer in CUDA and study its performance characteristics when used as a backend for adaptive tessellation down to micropolygons. Tessellation and bucketing map very well to the data-parallel paradigm of CUDA, and the majority of time is spent with rasterization. Despite this, our fastest implementation is able to reach 30-50% of the hardware rasterization performance of an Nvidia GTX 280. Overall we are able to rasterize 4 M textured and Phong shaded microquads into a 1600x1200 framebuffer at 10-12 fps.Abstract We implement a tile based sort-middle rasterizer in CUDA and study its performance characteristics when used as a backend for adaptive tessellation down to micropolygons. Tessellation and bucketing map very well to the data-parallel paradigm of CUDA, and the majority of time is spent with rasterization. Despite this, our fastest implementation is able to reach 30-50% of the hardware rasterization performance of an Nvidia GTX 280. Overall we are able to rasterize 4 M textured and Phong shaded microquads into a 1600x1200 framebuffer at 10-12 fps.
Efficient Free Path Sampling in Inhomogeneous Media
(The Eurographics Association, 2010) Szirmay-Kalos, László; Tóth, Balázs; Magdics, Milán; Csébfalvi, Balázs; Anders Hast and Ivan Viola
This paper presents an efficient algorithm to sample free path in inhomogeneous participating media. The method is based on the concept of mixing virtual particles to the medium, that complete the extinction coefficient to a piece-wise constant function. We use the sampling formulae developed for piece-wise homogeneous medium, but decide randomly whether a real or a virtual particle is hit.
Seamless Montage for Texturing Models
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Gal, Ran; Wexler, Yonatan; Ofek, Eyal; Hoppe, Hugues; Cohen-Or, Daniel
We present an automatic method to recover high-resolution texture over an object by mapping detailed photographs onto its surface. Such high-resolution detail often reveals inaccuracies in geometry and registration, as well as lighting variations and surface reflections. Simple image projection results in visible seams on the surface. We minimize such seams using a global optimization that assigns compatible texture to adjacent triangles. The key idea is to search not only combinatorially over the source images, but also over a set of local image transformations that compensate for geometric misalignment. This broad search space is traversed using a discrete labeling algorithm, aided by a coarse-to-fine strategy. Our approach significantly improves resilience to acquisition errors, thereby allowing simple and easy creation of textured models for use in computer graphics.
Hybrid Mesh Editing
(The Eurographics Association, 2010) Borosán, Péter; Howard, Reid; Zhang, Shaoting; Nealen, Andrew; H. P. A. Lensch and S. Seipel
Surface-based deformation and cage-based deformation are two popular shape editing paradigms. Surface-based methods are easy to use and produce high-quality results by preserving differential properties of the surface mesh, but are limited by their computational requirements. Cage-based methods produce results quickly but at the expense of usability and realism, and typically require manual construction of suitable cages. We introduce a hybrid approach that combines the two methods. The user can perform edits on an automatically-generated simplified version of an input shape using As-rigid-as-possible surface modeling, and the edit is propagated to the original shape by a precomputed space deformation based on Mean value coordinates. We analyze deformation quality and running time for a variety of cage sizes. High-quality results are obtained for meshes on the order of 100K vertices at interactive rates by using cages with app. 5% of the vertices of the original shape.
Tetrahedral Embedded Boundary Methods for Accurate and Flexible Adaptive Fluids
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Batty, Christopher; Xenos, Stefan; Houston, Ben
When simulating fluids, tetrahedral methods provide flexibility and ease of adaptivity that Cartesian grids find difficult to match. However, this approach has so far been limited by two conflicting requirements. First, accurate simulation requires quality Delaunay meshes and the use of circumcentric pressures. Second, meshes must align with potentially complex moving surfaces and boundaries, necessitating continuous remeshing. Unfortunately, sacrificing mesh quality in favour of speed yields inaccurate velocities and simulation artifacts. We describe how to eliminate the boundary-matching constraint by adapting recent embedded boundary techniques to tetrahedra, so that neither air nor solid boundaries need to align with mesh geometry. This enables the use of high quality, arbitrarily graded, non-conforming Delaunay meshes, which are simpler and faster to generate. Temporal coherence can also be exploited by reusing meshes over adjacent timesteps to further reduce meshing costs. Lastly, our free surface boundary condition eliminates the spurious currents that previous methods exhibited for slow or static scenarios. We provide several examples demonstrating that our efficient tetrahedral embedded boundary method can substantially increase the flexibility and accuracy of adaptive Eulerian fluid simulation.
A Spatially Adaptive Morphological Filter for Dual-Resolution Interface Tracking of Fluids
(The Eurographics Association, 2010) Söderström, Andreas; Museth, Ken; H. P. A. Lensch and S. Seipel
We present a novel surface-tracking technique for free-surface fluid animations. Unlike the semi-implicit Particle Level Set method (PLS) our interface-tracking approach is purely implicit and hence avoids some of the well-known issues like surface noise and inflated memory footprints. Where PLS augments the interface with Lagrangian tracker-particles, we instead employ a higher resolution level set represented as a DT-Grid. The synchronization of our dual-resolution level sets is facilitated by a novel Spatially Adaptive Morphological (SAM) filter that attempts to preserve fine details while still avoiding spurious topology changes and boundary violations. We demonstrate that our approach can achieve comparative results to the PLS, but with a fraction of the memory footprint. We also show how our technique can be used to effectively enhance thin interface sheets at the cost of volume gain.
A Survey of Real-Time Hard Shadow Mapping Methods
(The Eurographics Association, 2010) Scherzer, D.; Wimmer, M.; Purgathofer, W.; Helwig Hauser and Erik Reinhard
Due to its versatility, speed and robustness, shadow mapping has always been a popular algorithm for fast hard shadow generation since its introduction in 1978, first for off-line film productions and later increasingly so in real-time graphics. So it is not surprising that recent years have seen an explosion in the number of shadow map related publications. The last survey that encompassed shadow mapping approaches, but was mainly focused on soft shadow generation, dates back to 2003 [HLHS03], while the last survey for general shadow generation dates back to 1990 [WPF90]. No survey that describes all the advances made in hard shadow map generation in recent years exists. On the other hand, shadow mapping is widely used in the game industry, in production, and in many other applications, and it is the basis of many soft shadow algorithms. Due to the abundance of articles on the topic, it has become very hard for practitioners and researchers to select a suitable shadow algorithm, and therefore many applications miss out on the latest high-quality shadow generation approaches. The goal of this survey is to rectify this situation by providing a detailed overview of this field. We provide a detailed analysis of shadow mapping errors and derive from this a comprehensive classification of the existing methods. We discuss the most influential algorithms, consider their benefits and shortcomings and thereby provide the reader with the means to choose the shadow algorithm best suited to his or her needs.
Shared Sampling for Real-Time Alpha Matting
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Gastal, Eduardo S. L.; Oliveira, Manuel M.
Image matting aims at extracting foreground elements from an image by means of color and opacity (alpha) estimation. While a lot of progress has been made in recent years on improving the accuracy of matting techniques, one common problem persisted: the low speed of matte computation. We present the first real-time matting technique for natural images and videos. Our technique is based on the observation that, for small neighborhoods, pixels tend to share similar attributes. Therefore, independently treating each pixel in the unknown regions of a trimap results in a lot of redundant work. We show how this computation can be significantly and safely reduced by means of a careful selection of pairs of background and foreground samples. Our technique achieves speedups of up to two orders of magnitude compared to previous ones, while producing high-quality alpha mattes. The quality of our results has been verified through an independent benchmark. The speed of our technique enables, for the first time, real-time alpha matting of videos, and has the potential to enable a new class of exciting applications.
User-Controllable Color Transfer
(The Eurographics Association and Blackwell Publishing Ltd, 2010) An, Xiaobo; Pellacini, Fabio
This paper presents an image editing framework where users use reference images to indicate desired color edits. In our approach, users specify pairs of strokes to indicate corresponding regions in both the original and the reference image that should have the same color style . Within each stroke pair, a nonlinear constrained parametric transfer model is used to transfer the reference colors to the original. We estimate the model parameters by matching color distributions, under constraints that ensure no visual artifacts are present in the transfer result. To perform transfer on the whole image, we employ optimization methods to propagate the model parameters defined at each stroke location to spatially-close regions of similar appearance. This stroke-based formulation requires minimal user effort while retaining the high degree of user control necessary to allow artistic interpretations. We demonstrate our approach by performing color transfer on a number of image pairs varying in content and style, and show that our algorithm outperforms state-of-the-art color transfer methods on both user-controllability and visual qualities of the transfer results.

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