EG2012

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

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3D Material Style Transfer
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Nguyen, Chuong H.; Ritschel, Tobias; Myszkowski, Karol; Eisemann, Elmar; Seidel, Hans-Peter; P. Cignoni and T. Ertl
This work proposes a technique to transfer the material style or mood from a guide source such as an image or video onto a target 3D scene. It formulates the problem as a combinatorial optimization of assigning discrete materials extracted from the guide source to discrete objects in the target 3D scene. The assignment is optimized to fulfill multiple goals: overall image mood based on several image statistics; spatial material organization and grouping as well as geometric similarity between objects that were assigned to similar materials. To be able to use common uncalibrated images and videos with unknown geometry and lighting as guides, a material estimation derives perceptually plausible reflectance, specularity, glossiness, and texture. Finally, results produced by our method are compared to manual material assignments in a perceptual study.
Adaptation of Electrical Laboratory Systems through Augmented Reality for Optimization of Engineering Teaching University
(The Eurographics Association, 2012) Martín-Gutiérrez, Jorge; Fabiani, Peña; Meneses-Fernández, M. Dolores; Pérez-López, David C.; Abselán, Luis; Giovanni Gallo and Beatriz Sousa Santos
This paper introduces an Augmented Reality (AR) application for teaching practices of electrical engineering. In order to improve the autonomy of students and their self-ability we have developed several new practical AR-manuals for being used in the Electric Machines Laboratory. We have used these AR-manuals and the classic ones finding an improvement in learning and motivation of students. The augmented information consists of 3D models, animations and sounds which are superimposed over real objects helping the students in the training of specific tasks. The AR application and the learning environment have been designed based on the principles of interaction between man and machine so the virtual information is presented in an attractive way. Every user provided with a tablet PC or HMD with webcam will be able to visualize on screen the virtual objects added to the real scene. Only one mark has been included in the setting which allows visualization of the virtual information so just one gesture from the user is needed for changing the information. The interactive AR interface has been tested in the laboratory of electrical engineering at a Spanish university.
Advected Tangent Curves: A General Scheme for Characteristic Curves of Flow Fields
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Weinkauf, Tino; Hege, Hans-Christian; Theisel, Holger; P. Cignoni and T. Ertl
We present the first general scheme to describe all four types of characteristic curves of flow fields - stream, path, streak, and time lines - as tangent curves of a derived vector field. Thus, all these lines can be obtained by a simple integration of an autonomous ODE system. Our approach draws on the principal ideas of the recently introduced tangent curve description of streak lines. We provide the first description of time lines as tangent curves of a derived vector field, which could previously only be constructed in a geometric manner. Furthermore, our scheme gives rise to new types of curves. In particular, we introduce advected stream lines as a parameterfree variant of the time line metaphor. With our novel mathematical description of characteristic curves, a large number of feature extraction and analysis tools becomes available for all types of characteristic curves, which were previously only available for stream and path lines. We will highlight some of these possible applications including the computation of time line curvature fields and the extraction of cores of swirling advected stream lines.
Analytic Anti-Aliasing of Linear Functions on Polytopes
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Auzinger, Thomas; Guthe, Michael; Jeschke, Stefan; P. Cignoni and T. Ertl
This paper presents an analytic formulation for anti-aliased sampling of 2D polygons and 3D polyhedra. Our framework allows the exact evaluation of the convolution integral with a linear function defined on the polytopes. The filter is a spherically symmetric polynomial of any order, supporting approximations to refined variants such as the Mitchell-Netravali filter family. This enables high-quality rasterization of triangles and tetrahedra with linearly interpolated vertex values to regular and non-regular grids. A closed form solution of the convolution is presented and an efficient implementation on the GPU using DirectX and CUDA C is described.
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.
Automatic Line Handles for Freeform Deformation
(The Eurographics Association, 2012) Schemali, Leïla; Thiery, Jean-Marc; Boubekeur, Tamy; Carlos Andujar and Enrico Puppo
Interactive freeform surface deformation methods allow to explore the space of possible shapes using simple control structures. While recent advances in variational editing provide high quality deformations, designing control structures remains a time-consuming manual process. We propose a new automatic control structure generation based on the observation that the most salient visual structures of a surface, such as the one exploited in Line Drawing methods, are tightly linked to the potential deformations it may undergo. Our basic idea is to build control structures from those lines in order to provide users with an automatic set of deformation handles to grab and manipulate, avoiding the tedious task of region selection and handle positioning. The resulting interface inherits view-dependency and adaptivity from line definitions, reduces significantly the modeling session time in a number of scenarii, and remains fully compatible with classical handle-based deformations.
Automatic Multi-view Surface Matching
(The Eurographics Association, 2012) Fantoni, Simone; Castellani, Umberto; Fusiello, Andrea; Carlos Andujar and Enrico Puppo
In this paper we tackle the problem of automatically aligning an unordered set of range views. We propose a full pipeline that goes from the scans to the complete 3D model. The emphasis is on the automation no manual intervention is require and on the fact that no knowledge on the acquisition sequence is assumed. The contribution is twofold: in the pre-alignment phase a voting scheme is proposed that discovers the overlapping relationship among views; in the final refinement step we extend the Levenberg Marquardt-ICP to work with multiple views, in order to solve for the absolute pose of all images simultaneously.
Automatically Rigging Multi-component Characters
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Bharaj, Gaurav; Thormählen, Thorsten; Seidel, Hans-Peter; Theobalt, Christian; P. Cignoni and T. Ertl
Rigging an arbitrary 3D character by creating an animation skeleton is a time-consuming process even for experienced animators. In this paper, we present an algorithm that automatically creates animation rigs for multicomponent 3D models, as they are typically found in online shape databases. Our algorithm takes as input a multi-component model and an input animation skeleton with associated motion data. It then creates a target skeleton for the input model, calculates the rigid skinning weights, and a mapping between the joints of the target skeleton and the input animation skeleton. The automatic approach does not need additional semantic information, such as component labels or user-provided correspondences, and succeeds on a wide range of models where the number of components is significantly different. It implicitly handles large scale and proportional differences between input and target skeletons and can deal with certain morphological differences, e.g., if input and target have different numbers of limbs. The output of our algorithm can be directly used in a retargeting system to create a plausible animated character.
Black is Green: Adaptive Color Transformation For Reduced Ink Usage
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Shapira, Lior; Oicherman, Boris; P. Cignoni and T. Ertl
A vast majority of color transformations applied to an image in the digital press industry are static and precalculated. In order to achieve the best quality on a wide variety of different images, these transformations tend to be highly conservative with respect to the use of black ink. This results in excessive use of inks, which has a negative economic and environmental impact. We present a method for dynamic computation of color transformation based on image content, with the aim to reduce ink usage. We analyze the image, and predict areas in which quality artifacts that may result from such a reduction will be masked by the image content. These areas include detailed textures, noisy areas and structure. We then replace the image CMYK values by a new combination with increased black. Our algorithm ensures negligible color shifts in the resulting image, and no visible reduction in quality. We achieve an average of over 10% ink savings.
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 Cell-Based Light Interaction Model for Human Blood
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Yim, Daniel; Baranoski, Gladimir V. G.; Kimmel, Brad W.; Chen, T. Francis; Miranda, Erik; P. Cignoni and T. Ertl
The development of predictive appearance models for organic tissues is a challenging task due to the inherent complexity of these materials. In this paper, we closely examine the biophysical processes responsible for the appearance attributes of whole blood, one the most fundamental of these materials. We describe a new appearance model that simulates the mechanisms of light propagation and absorption within the cellular and fluid portions of this specialized tissue. The proposed model employs a comprehensive, and yet flexible first principles approach based on the morphological, optical and biochemical properties of blood cells. This approach allows for environment driven changes in the cells' anatomy and orientation to be appropriately included into the light transport simulations. The correctness and predictive capabilities of the proposed model are quantitatively and qualitatively evaluated through comparisons of modeled results with actual measured data and experimental observations reported in the scientific literature. Its incorporation into rendering systems is illustrated through images of blood samples depicting appearance variations controlled by physiologically meaningful parameters. Besides the contributions to the modeling of material appearance, the research presented in this paper is also expected to have applications in a wide range of biomedical areas, from optical diagnostics to the visualization and noninvasive imaging of blood-perfused tissues.
Centroidal Voronoi Tessellation of Line Segments and Graphs
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Lu, Lin; Lévy, Bruno; Wang, Wenping; P. Cignoni and T. Ertl
Centroidal Voronoi Tessellation (CVT) of points has many applications in geometry processing, including remeshing and segmentation, to name but a few. In this paper, we generalize the CVT concept to graphs via a variational characterization. Given a graph and a 3D polygonal surface, our method optimizes the placement of the vertices of the graph in such a way that the graph segments best approximate the shape of the surface. We formulate the computation of CVT for graphs as a continuous variational problem, and present a simple, approximate method for solving this problem. Our method is robust in the sense that it is independent of degeneracies in the input mesh, such as skinny triangles, T-junctions, small gaps or multiple connected components. We present some applications, to skeleton fitting and to shape segmentation.
Coding Depth through Mask Structure
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Fortunato, Horacio E.; Oliveira, Manuel M.; P. Cignoni and T. Ertl
We present a coded-aperture method based on a family of masks obtained as the convolution of one "hole" with a structural component consisting of an arrangement of Dirac delta functions. We call the arrangement of delta functions the structural component of the mask, and use it to efficiently encode scene distance information. We illustrate the potential of our approach by analyzing a family of masks defined by a circular hole component and a structural component consisting of a linear combination of three Dirac deltas. We show that the structural component transitions from well conditioned to ill conditioned as the relative weight of the central peak varies with respect to the lateral ones. For the well-conditioned structural components, deconvolution is efficiently performed by inverse filtering, allowing for fast estimation of scene depth. We demonstrate the effectiveness of our approach by constructing a mask for distance coding and using it to recover pairs of distance maps and structurally-deconvolved images from single photographs. For this application, we obtain significant speedup, and extended range and depth resolution compared to previous techniques.
Coherent Spatiotemporal Filtering, Upsampling and Rendering of RGBZ Videos
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Richardt, Christian; Stoll, Carsten; Dodgson, Neil A.; Seidel, Hans-Peter; Theobalt, Christian; P. Cignoni and T. Ertl
Sophisticated video processing effects require both image and geometry information. We explore the possibility to augment a video camera with a recent infrared time-of-flight depth camera, to capture high-resolution RGB and low-resolution, noisy depth at video frame rates. To turn such a setup into a practical RGBZ video camera, we develop efficient data filtering techniques that are tailored to the noise characteristics of IR depth cameras. We first remove typical artefacts in the RGBZ data and then apply an efficient spatiotemporal denoising and upsampling scheme. This allows us to record temporally coherent RGBZ videos at interactive frame rates and to use them to render a variety of effects in unprecedented quality. We show effects such as video relighting, geometry-based abstraction and stylisation, background segmentation and rendering in stereoscopic 3D.
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.
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.
Computational Design of Rubber Balloons
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Skouras, Mélina; Thomaszewski, Bernhard; Bickel, Bernd; Gross, Markus; P. Cignoni and T. Ertl
This paper presents an automatic process for fabrication-oriented design of custom-shaped rubber balloons. We cast computational balloon design as an inverse problem: given a target shape, we compute an optimal balloon that, when inflated, approximates the target as closely as possible. To solve this problem numerically, we propose a novel physics-driven shape optimization method, which combines physical simulation of inflatable elastic membranes with a dedicated constrained optimization algorithm. We validate our approach by fabricating balloons designed with our method and comparing their inflated shapes to the results predicted by simulation. An extensive set of manufactured sample balloons demonstrates the shape diversity that can be achieved by our method.
A Computational Model of Afterimages
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Ritschel, Tobias; Eisemann, Elmar; P. Cignoni and T. Ertl
Afterimages are optical illusions, particularly well perceived when fixating an image for an extended period of time and then looking at a neutral background, where an inverted copy of the original stimulus appears. The full mechanism that produces the perceived specific colors and shapes is complex and not entirely understood, but most of the important attributes can be well explained by bleaching of retinal photoreceptors (retinal kinetics). We propose a model to compute afterimages that allows us to simulate their temporal, color and time-frequency behavior. Using this model, high dynamic range (HDR) content can be processed to add realistic afterimages to low dynamic range (LDR) media. Hereby, our approach helps in conveying the original source's luminance and contrast. It can be applied in real-time on full-HD HDR content using standard graphics hardware. Finally, our approach is validated in a perceptual study.
Consistent Media Model for Real-Time Scene Rendering
(The Eurographics Association, 2012) Belhadj, Farès; Suarez, Jordane; Boyer, Vincent; Andrea Fusiello and Michael Wimmer
We present a consistent model for artistic media reproduction in 3D scene renderings and animations. Artistic media reproduction can be defined as a media model (such as brush, pencil, ink) and a support (such as canvas and papers). We create a surface grain according to the object geometry and apply it as additional material properties. Furthermore, we propose to use the abstraction of obtained results as an entry of a fractal surface reconstruction process that provides additional effects of traditional media such as brush stroke effects. Our model is fully implemented on GPU and the rendering process is strongly real-time.
A Continuous, Editable Representation for Deforming Mesh Sequences with Separate Signals for Time, Pose and Shape
(The Eurographics Association and John Wiley and Sons Ltd., 2012) Cashman, Thomas J.; Hormann, Kai; P. Cignoni and T. Ertl
It is increasingly popular to represent non-rigid motion using a deforming mesh sequence: a discrete sequence of frames, each of which is given as a mesh with a common graph structure. Such sequences have the flexibility to represent a wide range of mesh deformations used in practice, but they are also highly redundant, expensive to store, and difficult to edit in a time-coherent manner. We address these limitations with a continuous representation that extracts redundancy in three separate phases, leading to separate editable signals in time, pose and shape. The representation can be applied to any deforming mesh sequence, in contrast to previous domain-specific approaches. By modifying the three signal components, we demonstrate time-coherent editing operations such as local repetition of part of a sequence, frame rate conversion and deformation transfer. We also show that our representation makes it possible to design new deforming sequences simply by sketching a curve in a 2D pose space.

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