EG2012

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https://diglib.eg.org/handle/10.2312/292

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Building a Serious Game to Teach Secure Coding in Introductory Programming Courses
(The Eurographics Association, 2012) Adamo-Villani, Nicoletta; Oania, Marcus; Whittinghill, David; Brown, Jacob; Cooper, Stephen; Giovanni Gallo and Beatriz Sousa Santos
We report the development and initial evaluation of a serious game that, in conjunction with appropriately designed matching laboratory exercises, can be used to teach secure coding and Information Assurance (IA) concepts across a range of introductory computing courses. The IA Game is a role-playing serious game (RPG) in which the student travels through seven computer techno-inspired environments (IA concept rooms); in each environment he/she learns a different IA concept. After playing each level, the student completes a related CS educational module comprised of a theory lesson and a lab assignment. The game is being created with a user-centered iterative approach that includes two forms of evaluation: formative and summative. In this paper we report the findings of an initial formative evaluation of the first 2 game levels with a group of undergraduate students.
A Survey of Urban Reconstruction
(The Eurographics Association, 2012) Musialski, Przemyslaw; Wonka, Peter; Aliaga, Daniel G.; Wimmer, Michael; Gool, Luc van; Purgathofer, Werner; Marie-Paule Cani and Fabio Ganovelli
This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under very active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision, and photogrammetry and remote sensing. Our goal is to provide a survey that will help researchers to better position their own work in the context of existing solutions, and to help newcomers and practitioners in computer graphics to quickly gain an overview of this vast field. Further, we would like to bring the mentioned research communities to even more interdisciplinary work, since the reconstruction problem itself is by far not solved.
Realtime 3D Sensor Based Air Flow Reconstruction
(The Eurographics Association, 2012) Dyck, Michiel Van; Peremans, Herbert; Andrea Fusiello and Michael Wimmer
Based on state-of-the art bio-inspired air flow sensors it becomes possible to capture air flow velocity and direction at multiple locations at the same time instance. These sensor values can be used in a simulation environment to visualize and examine the captured air flow pattern. The simulation environment makes interpolations of the flow between the sensors based on the Navier-Stokes equations. These equations can be solved efficiently using a stable approximation technique described by J Stam and making use of the enormous parallel computing power available through the latest graphical processing boards.
Forward+: Bringing Deferred Lighting to the Next Level
(The Eurographics Association, 2012) Harada, Takahiro; McKee, Jay; Yang, Jason C.; Carlos Andujar and Enrico Puppo
This paper presents Forward+, a method of rendering many lights by culling and storing only lights that contribute to the pixel. Forward+ is an extension to traditional forward rendering. Light culling, implemented using the compute capability of the GPU, is added to the pipeline to create lists of lights; that list is passed to the final rendering shader, which can access all information about the lights. Although Forward+ increases workload to the final shader, it theoretically requires less memory traffic compared to compute-based deferred lighting. Furthermore, it removes the major drawback of deferred techniques, which is a restriction of materials and lighting models. Experiments are performed to compare the performance of Forward+ and deferred lighting.
Automatic Alignment of Shape Collections
(The Eurographics Association, 2012) Averkiou, Melinos; Mitra, Niloy; Andrea Fusiello and Michael Wimmer
We present a method for automatically aligning a collection of similar shapes in arbitrary initial poses. By analyzing the shape collection we extract a deformation model to capture the variability in the collection. We use this information to deform an extracted template shape and use it to align pairs of shapes by direct PCA alignment. We evaluate our method on synthetically created model collections in arbitrary initial poses and demonstrate accurate results with near ground truth alignment. Our algorithm significantly outperforms existing direct PCA alignment methods, without significant computational overhead.
Scented Sliders for Procedural Textures
(The Eurographics Association, 2012) Lasram, Anass; Lefebvre, Sylvain; Damez, Cyrille; Carlos Andujar and Enrico Puppo
Procedural textures often expose a set of parameters controlling their final appearance. This lets end users tune the final look and feel, typically through a set of sliders. However, it is difficult to predict the changes introduced by a given slider, especially as sliders interact in non–trivial ways. We augment the sliders controlling parameters with visual previews revealing the changes that will be introduced upon manipulation. These previews are constantly refreshed to reflect changes with respect to the current settings. The main challenge is to generate the visual sliders in a very limited pixel space and at an interactive rate. This is done by synthesizing the visual slider from a small set of patches ordered in accordance with the slider. These patches are chosen so as to reveal as much as possible the visual variations induced by the slider. The selection and ordering are achieved by using the seam–carving algorithm to carve patches with low visual impact. The obtained patches are then stitched together using patch-based texture synthesis to form the final visual slider.
FTLE Computation Beyond First-Order Approximation
(The Eurographics Association, 2012) Üffinger, Markus; Sadlo, Filip; Kirby, Mike; Hansen, Charles; Ertl, Thomas; Carlos Andujar and Enrico Puppo
We present a framework for different approaches to finite-time Lyapunov exponent (FTLE) computation for 2D vector fields, based on the advection of seeding circles. On the one hand it unifies the popular flow map approach with techniques based on the evaluation of distinguished trajectories, such as renormalization. On the other hand it allows for the exploration of their order of approximation (first-order approximation representing the flow map gradient). Using this framework, we derive a measure for nonlinearity of the flow map, that brings us to the definition of a new FTLE approach. We also show how the nonlinearity measure can be used as a criterion for flow map refinement for more accurate FTLE computation, and we demonstrate that ridge extraction in supersampled FTLE leads to superior ridge quality.
Preface and Table of Contents
(The Eurographics Association and Blackwell Publishing Ltd., 2012) P. Cignoni and T. Ertl
Combining Structure from Motion and Photometric Stereo: A Piecewise Formulation
(The Eurographics Association, 2012) Sabzevari, Reza; Bue, Alessio Del; Murino, Vittorio; Andrea Fusiello and Michael Wimmer
This paper introduces a novel piecewise formulation for Photometric Stereo on static scenes exploiting a set of multiple view constraints on the surface. Such constraints will help to recover geometrical properties of the object and to eliminate the global bas-relief ambiguity. On the other hand, the proposed piecewise formulation will help to model more complex photometric properties of the surfaces using local lighting models. The experimental results show performance of the proposed method against 3D ground truth.
Minimising Longest Edge for Closed Surface Construction from Unorganised 3D Point Sets
(The Eurographics Association, 2012) Ohrhallinger, Stefan; Mudur, Sudhir; Andrea Fusiello and Michael Wimmer
Given an unorganised 3D point set with just coordinate data, we formulate the problem of closed surface construction as one requiring minimisation of longest edge in triangles, a criterion derivable from Gestalt laws for shape perception. Next we define the Minimum Boundary Complex (BCmin), which resembles the desired surface Bmin considerably, by slightly relaxing the topological constraint to make it at least two triangles per edge instead of exactly two required by Bmin. A close approximation of BCmin can be computed fast using a greedy algorithm. This provides a very good starting shape which can be transformed by a few steps into the desired shape, close to Bmin. Our method runs in O(nlogn) time, with Delaunay Graph construction as largest run-time factor. We show considerable improvement over previous methods, especially for sparse, non-uniform point spacing.
Combining Texture Streaming and Run-Time Generation
(The Eurographics Association, 2012) Demeulemeester, Aljosha; Hollemeersch, Charles-Frederik; Pieters, Bart; Lambert, Peter; Walle, Rik Van de; Andrea Fusiello and Michael Wimmer
Virtual texturing systems have enabled gigapixel resolutions for textures used in real-time rendering. This allows for more detail and diversity in virtual worlds at the cost of greatly increasing disc storage requirements. In this paper, we propose a compression method that generates parts of these large textures at run-time using the original painting primitives (brushes) from the texture production process. This way, large featureless texture areas can be compressed to a few brush resources. A post-production analyzing phase determines those areas that should be stored as compressed texel data to ensure real-time performance at run-time.
Growing Cell Structures Learning a Progressive Mesh During Surface Reconstruction - A Top-Down Approach
(The Eurographics Association, 2012) Vierjahn, Tom; Lorenz, Guido; Mostafawy, Sina; Hinrichs, Klaus; Carlos Andujar and Enrico Puppo
Growing Cell Structures (GCS) have been proven to be suitable for surface reconstruction from unstructured point clouds. The reconstructed triangle mesh can be represented compactly as a progressive mesh with integrated level of detail by storing only vertex split operations. However, half-edge collapse operations are used for GCS. In this paper, we present an improvement to a GCS-based surface reconstruction technique by converting a halfedge collapse to a more general vertex removal to create a progressive mesh. We have evaluated the new technique with respect to running time overhead and mesh quality. Results indicate that this technique can be used for efficient surface reconstruction. We will use the presented findings as basis for future research.
Teaching a Modern Graphics Pipeline Using a Shader-based Software Renderer
(The Eurographics Association, 2012) Fink, Heinrich; Weber, Thomas; Wimmer, Michael; Giovanni Gallo and Beatriz Sousa Santos
Shaders are a fundamental pattern of the modern graphics pipeline. This paper presents a syllabus for an introductory computer graphics course that emphasizes the use of programmable shaders while teaching raster-level algorithms at the same time. We describe a Java-based framework that is used for programming assignments in this course. This framework implements a shader-enabled software renderer and an interactive 3D editor. We also show how to create attractive course materials by using COLLADA, an open standard for 3D content exchange.
Hyperplane Culling for Stochastic Rasterization
(The Eurographics Association, 2012) Munkberg, Jacob; Akenine-Möller, Tomas; Carlos Andujar and Enrico Puppo
We present two novel culling tests for rasterization of simultaneous depth of field and motion blur. These tests efficiently reduce the set of xyuvt samples that need to be coverage tested within a screen space tile. The first test finds linear bounds in ut- and vt-space using a separating line algorithm. We also derive a hyperplane in xyuvtspace for each triangle edge, and all samples outside of these planes are culled in our second test. Based on these tests, we present an efficient stochastic rasterizer, which has substantially higher sample test efficiency and lower arithmetic cost than previous tile-based stochastic rasterizers.
On User-Interaction in 3D Reconstruction
(The Eurographics Association, 2012) Schneider, David C.; Eisert, Peter; Andrea Fusiello and Michael Wimmer
For many computer graphics tasks such as segmentation, tracking or retargeting, algorithms are designed to allow user interaction. For real-world applications, tools which give users some form of control are often preferred over fully automatic ones. In 3D reconstruction, however, algorithms are typically non-interactive and errors are corrected after reconstruction in generic 3D modeling software. In this contribution, we discuss fundamental algorithmic considerations regarding interactivity in 3D reconstruction and we outline an optimization-based reconstruction framework which allows the incorporation of interactive tools as energy terms.
Interactive Volume Rendering with Volumetric Illumination
(The Eurographics Association, 2012) Jönsson, Daniel; Sundén, Erik; Ynnerman, Anders; Ropinski, Timo; Marie-Paule Cani and Fabio Ganovelli
Interactive volume rendering in its standard formulation has become an increasingly important tool in many application domains. In recent years several advanced volumetric illumination techniques to be used in interactive scenarios have been proposed. These techniques claim to have perceptual benefits as well as being capable of producing more realistic volume rendered images. Naturally, they cover a wide spectrum of illumination effects, including varying shadowing and scattering effects. In this article, we review and classify the existing techniques for advanced volumetric illumination. The classification will be conducted based on their technical realization, their performance behavior as well as their perceptual capabilities. Based on the limitations revealed in this review, we will define future challenges in the area of interactive advanced volumetric illumination.
Shape Reconstruction from Raw Point Clouds using Depth Carving
(The Eurographics Association, 2012) Guggeri, Fabio; Scateni, Riccardo; Pajarola, Renato; Carlos Andujar and Enrico Puppo
Shape reconstruction from raw point sets is a hot research topic. Point sets are increasingly available as primary input source, since low-cost acquisition methods are largely accessible nowadays, and these sets are more noisy than used to be. Standard reconstruction methods rely on normals or signed distance functions, and thus many methods aim at estimating these features. Human vision can however easily discern between the inside and the outside of a dense cloud even without the support of fancy measures. We propose, here, a perceptual method for estimating an indicator function for the shape, inspired from image-based methods. The resulting function nicely approximates the shape, is robust to noise, and can be used for direct isosurface extraction or as an input for other accurate reconstruction methods.
Variation-Factored Encoding of Facade Images
(The Eurographics Association, 2012) Alsisan, Suhib; Mitra, Niloy J.; Carlos Andujar and Enrico Puppo
Urban facades contain large-scale repetitions in the form of windows, doors, etc. Such elements often are in different configurations (e.g., open or closed) obscuring their regular arrangements to any direct low-level pixel matching based repetition detection.We propose a variation-factored representation for facade images by progressively favoring larger repeated structures while allowing relabeling using candidate element types. We formulate the problem as a Markov Random Field (MRF) based optimization, and evaluate the algorithm on a large number of benchmark facade images. Such a facade encoding is very compact and can be used for rapid generation of realistic 3D models with variations suitable for online map viewers or mobile navigation aids.
Efficient Evaluation of Semi-Smooth Creases in Catmull-Clark Subdivision Surfaces
(The Eurographics Association, 2012) Nießner, Matthias; Loop, Charles; Greiner, Günther; Carlos Andujar and Enrico Puppo
We present a novel method to evaluate semi-smooth creases in Catmull-Clark subdivision surfaces. Our algorithm supports both integer and fractional crease tags corresponding to the RenderMan (Pixar) specification. In order to perform fast and efficient surface evaluations, we obtain a polynomial surface representation given by the semismooth subdivision rules. While direct surface evaluation is applied for regular patches, we perform adaptive subdivision around extraordinary vertices. In the end, we are able to efficently handle high-order sharpness tags at very low cost. Compared to the state-of-the art, both render time and memory consumption are reduced from exponential to linear complexity. Furthermore, we integrate our algorithm in the hardware tessellation pipeline of modern GPUs. Our method is ideally suited to real-time applications such as games or authoring tools.
Multiview-Consistent Color Sampling for Alpha Matting
(The Eurographics Association, 2012) Kettern, Markus; Eisert, Peter; Andrea Fusiello and Michael Wimmer
We propose a method for incorporating multiview information into color sampling methodologies for alpha matting. We extend the typical trimap input for matting algorithms to 3D space, enabling the association of stripes of pixels in semi-transparent regions like hair between different views without knowing or inferring their spatial structure. We also formulate a new cost function penalizing deviations of foreground color estimates between associated pixel stripes and its possible integration into a state-of-the-art color sampling approach.

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