EG2021

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https://diglib.eg.org/handle/10.2312/2633001

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Modeling and Actuation of Cable-driven Silicone Soft Robots
(The Eurographics Association, 2021) Frâncu, Mihail; Theisel, Holger and Wimmer, Michael
In this paper we present a framework for modeling cable-driven soft robots fabricated from silicone rubber - an incompressible material. Our forward simulation model can use either the standard or the mixed formulation of the finite element method (FEM). The latter prevents volumetric locking for incompressible materials and is more accurate for low resolution meshes. Hence, we show that mixed FEM is well suited for estimating elastic parameters and simulator validation. We also introduce a cable actuation model using barycentric coordinates and then use it to solve some simple control problems.
Visualization and Graphics in Mixed Reality
(The Eurographics Association, 2021) Kalkofen, Denis; Mori, Shohei; Tatzgern, Markus; O'Sullivan, Carol and Schmalstieg, Dieter
This tutorial will present the challenges and unique aspects of mixed reality visualization applications such as organization of data for visualization, real-world data sources for visualization, real time photo-realistic rendering techniques, diminished reality rendering techniques and cognitive and perceptual issues. We are also interested in ways that the existing body of research in the graphics and visualization community can be applied in this research area. We expect the tutorial to be a working event with both presentation of state-of- the-art followed by lively discussion about the key issues and challenges in this research area. Our tutorial is open both for academia and industry, and expected to be a community hub for both areas that are interested in an introduction to the unique challenges of mixed reality visualization. We welcome a diverse audience consisting of students, researchers and developers that have a basic understanding of computer graphics and computer vision.
Marching Cubes for Teaching GLSL Programming
(The Eurographics Association, 2021) Ilinkin, Ivaylo; Sousa Santos, Beatriz and Domik, Gitta
This paper shares ideas for illustrating GLSL programming based on the classic Marching Cubes algorithm. The algorithm has a number of appealing aspects: it is feasible to implement as one of the components in a computer graphics course, it motivates naturally a number of GLSL concepts and constructs, and leaves the students with a sense of accomplishment having reproduced original research. The paper suggest possible variations and extensions that could form the basis for final group projects.
Algorithms for Microscopic Crowd Simulation: Advancements in the 2010s
(The Eurographics Association and John Wiley & Sons Ltd., 2021) Toll, Wouter van; Pettré, Julien; Bühler, Katja and Rushmeier, Holly
The real-time simulation of human crowds has many applications. Simulating how the people in a crowd move through an environment is an active and ever-growing research topic. Most research focuses on microscopic (or 'agent-based') crowdsimulation methods that model the behavior of each individual person, from which collective behavior can then emerge. This state-of-the-art report analyzes how the research on microscopic crowd simulation has advanced since the year 2010. We focus on the most popular research area within the microscopic paradigm, which is local navigation, and most notably collision avoidance between agents. We discuss the four most popular categories of algorithms in this area (force-based, velocity-based, vision-based, and data-driven) that have either emerged or grown in the last decade. We also analyze the conceptual and computational (dis)advantages of each category. Next, we extend the discussion to other types of behavior or navigation (such as group behavior and the combination with path planning), and we review work on evaluating the quality of simulations. Based on the observed advancements in the 2010s, we conclude by predicting how the research area of microscopic crowd simulation will evolve in the future. Overall, we expect a significant growth in the area of data-driven and learning-based agent navigation, and we expect an increasing number of methods that re-group multiple 'levels' of behavior into one principle. Furthermore, we observe a clear need for new ways to analyze (real or simulated) crowd behavior, which is important for quantifying the realism of a simulation and for choosing the right algorithms at the right time.
EUROGRAPHICS 2021: Posters Frontmatter
(Eurographics Association, 2021) Bittner, Jirí; Waldner, Manuela; Bittner, Jirí and Waldner, Manuela
A Survey of Control Mechanisms for Creative Pattern Generation
(The Eurographics Association and John Wiley & Sons Ltd., 2021) Gieseke, Lena; Asente, Paul; Mech, Radomir; Benes, Bedrich; Fuchs, Martin; Bühler, Katja and Rushmeier, Holly
We review recent methods in 2D creative pattern generation and their control mechanisms, focusing on procedural methods. The review is motivated by an artist's perspective and investigates interactive pattern generation as a complex design problem. While the repetitive nature of patterns is well-suited to algorithmic creation and automation, an artist needs more flexible control mechanisms for adaptable and inventive designs. We organize the state of the art around pattern design features, such as repetition, frames, curves, directionality, and single visual accents. Within those areas, we summarize and discuss the techniques' control mechanisms for enabling artist intent. The discussion includes questions of how input is given by the artist, what type of content the artist inputs, where the input affects the canvas spatially, and when input can be given in the timeline of the creation process. We categorize the available control mechanisms on an algorithmic level and categorize their input modes based on exemplars, parameterization, handling, filling, guiding, and placing interactions. To better understand the potential of the current techniques for creative design and to make such an investigation more manageable, we motivate our discussion with how navigation, transparency, variation, and stimulation enable creativity. We conclude our review by identifying possible new directions that can inspire innovation for artist-centered creation processes and algorithms.
Teaching 3D Computer Animation to Non-programming Experts
(The Eurographics Association, 2021) Casas, Dan; Sousa Santos, Beatriz and Domik, Gitta
This paper describes a Computer Animation course aimed at novice Computer Science and Engineering students with minimal programming skills. We observe that students enrolled in Computer Graphics (and related) undergraduate degrees usually face a Computer Animation subject early in their programs, sometimes even before they develop strong software development and programming skills. This causes that assignments and tasks where students should focus on the Computer Animation concepts, end up in frustration and massive efforts to just get over-complicated developing frameworks running. Instead, we propose a Computer Animation course based on small MATLAB tasks that covers a large range of topics and it is adapted to students with minimal programming skills. For each topic, we provide a brief theoretical summary and links to fundamental literature, as well as a set of hands-on tasks with the necessary source code to get started. A user study shows that students who took this course were able to better focus on the fundamental concepts of the subject, circumventing the need to learn advanced programming skills. Course material is available on a public GitHub repository, and solutions are provided upon request from course tutors.
Project in Visualization and Data Analysis: Experiences in Designing and Coordinating the Course
(The Eurographics Association, 2021) Kucher, Kostiantyn; Martins, Rafael M.; Kerren, Andreas; Sousa Santos, Beatriz and Domik, Gitta
Visual analytics involves both visual and computational components for empowering human analysts who face the challenges of making sense and making use of large and heterogeneous data sets in various application domains. In order to facilitate the learning process for the students at higher education institutions with regard to both the theoretical knowledge and practical skills in visual analytics, the respective courses must cover a variety of topics and include multiple assessment methods and activities. In this paper, we report on the design and first instantiation of a full term project-based course in visualization and data analysis, which was recently offered to graduate and post-graduate students at our department and met with positive feedback from the course participants.
Inverse Computational Spectral Geometry
(The Eurographics Association, 2021) Rodolà, Emanuele; Melzi, Simone; Cosmo, Luca; Bronstein, Michael; Ovsjanikov, Maks; O'Sullivan, Carol and Schmalstieg, Dieter
In the last decades, geometry processing has attracted a growing interest thanks to the wide availability of new devices and software that make 3D digital data available and manipulable to everyone. Typical issues that are faced by geometry processing algorithms include the variety of discrete representations for 3D data (point clouds, polygonal or tet-meshes and voxels), or the type of deformation this data may undergo. Powerful approaches to address these issues come from looking at the spectral decomposition of canonical differential operators, such as the Laplacian, which provides a rich, informative, robust, and invariant representation of the 3D objects. Reasoning about spectral quantities is at the core of spectral geometry, which has enabled unprecedented performance in many tasks of computer graphics (e.g., shape matching with functional maps, shape retrieval, compression, and texture transfer), as well as contributing in opening new directions of research. The focus of this tutorial is on inverse computational spectral geometry. We will offer a different perspective on spectral geometric techniques, supported by recent successful methods in the graphics and 3D vision communities, as well as older, but notoriously overlooked results. Here, the interest shifts from studying the “forward” path typical of spectral geometry pipelines (e.g., computing Laplacian eigenvalues and eigenvectors of a given shape) to studying the inverse path (e.g., recovering a shape from given Laplacian eigenvalues, like in the classical “hearing the shape of the drum” problem). As is emblematic of inverse problems, the ill-posed nature of the reverse direction requires additional effort, but the benefits can be quite considerable as showcased on several challenging tasks in graphics and geometry processing. The purpose of the tutorial is to overview the foundations and the current state of the art on inverse computational spectral geometry, to highlight the main benefits of inverse spectral pipelines, as well as their current limitations and future developments in the context of computer graphics. The tutorial is aimed at a wide audience with a basic understanding of geometry processing, and will be accessible and interesting to students, researchers and practitioners from both the academia and the industry.
Color Reproduction Framework for Inkjet FDM 3D Printers
(The Eurographics Association, 2021) Silapasuphakornwong, Piyarat; Punpongsanon, Parinya; Panichkriangkrai, Chulapong; Sueeprasan, Suchitra; Uehira, Kazutake; Bittner, Jirí and Waldner, Manuela
Recent advances in consumer-grade 3D printers have enabled the fabrication of personal artifacts in aesthetically pleasing full color. However, the printed colors are usually different from the actual user desired colors due to the mismatching of droplets when the color reproduction workflow has been changed or the color profile setup is missing. In this paper, we present a preliminary experiment to investigate color reproduction errors in consumer-grade inkjet FDM 3D printers. Our results suggest that solving the problem requires initiating the workflow to minimize color reproduction errors such as using CMYK or sRGB color profiles. We also found that the mismatched color gamut between the input's desired texture and the 3D printed output depends on different file formats, and this finding requires future investigation.
EUROGRAPHICS 2021: CGF 40-2 STARs Frontmatter
(The Eurographics Association and John Wiley & Sons Ltd., 2021) Bühler, Katja; Rushmeier, Holly; Bühler, Katja and Rushmeier, Holly
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Tetrahedral Interpolation on Regular Grids
(The Eurographics Association, 2021) Bán, Róbert; Valasek, Gábor; Bittner, Jirí and Waldner, Manuela
This work proposes the use of barycentric interpolation on enclosing simplices of sample points to infer a reconstructed function from discrete data. In particular, we compare the results of trilinear and tetrahedral interpolation over regular 3D grids of second order spherical harmonics (SH) light probes. In general, tetrahedral interpolation only requires four data samples per query in contrast to the 8 samples necessary for trilinear interpolation, at the expense of a more expensive weight computation. Our tetrahedral implementation subdivides the cubical cells into six tetrahedra and uses the barycentric coordinates of the query position as weights to blend the probe data. We show that barycentric coordinates can be calculated efficiently in shaders for our particular tetrahedral decomposition of the cube, resulting only in simple arithmetic and conditional move operations.
Automatic Hierarchical Arrangement of Vector Designs
(The Eurographics Association, 2021) Fisher, Matthew; Agarwal, Vineet; Beri, Tarun; Theisel, Holger and Wimmer, Michael
We present a method that transforms an unstructured vector design into a logical hierarchy of groups of objects. Each group is a meaningful collection, formed by proximity in visual characteristics (like size, shape, color, etc.) and spatial location of objects and models the grouping principles designers use. We first simplify the input design by partially or completely flattening it and isolate duplicate geometries in the design (for example, repeating patterns due to copy and paste operations). Next we build the object containment hierarchy by assigning objects that are wholly enclosed inside the geometry of other objects as children of the enclosing parent. In the final clustering phase, we use agglomerative clustering to obtain a bottom-up hierarchical grouping of all objects by comparing and ranking all pairs of objects according to visual and spatial characteristics. Spatial proximity segregates far apart objects, but when they are identical (or near identical) designers generally prefer to keep (and edit) them together. To accommodate this, we detect near identical objects and group them together during clustering despite their spatial separation. We further restrict group formation so that z-order disturbances in the design keep the visual appearance unaffected for tightly-overlapping geometry. The generated organization is equivalent to the original design and the organization results are used to facilitate abstract navigation (hierarchical, lateral or near similar) and selections in the design. Our technique works well with a variety of input designs with commonly identifiable objects and structural patterns.
Rendering 2D Vector Graphics on Mobile GPU Devices
(The Eurographics Association, 2021) Kumar, Harish; Sud, Anmol; Bittner, Jirí and Waldner, Manuela
Designers and artists world-wide rely on vector graphics to design and edit 2D artwork, illustrations and typographic content. There is a recent trend of vector graphic applications moving to mobile platforms such as iPads, iPhone and mobile phones and with that there is new interest in optimised techniques of rendering vector graphics on these devices. These vector applications are not read only but also requires real time vector editing experience. Our solution builds upon standard 'stencil then cover' paradigm and develops an algorithm targeted for GPUs based on tile based deferred rendering architecture. Our technique provides an efficient way to use signed distance based anti-aliasing techniques with 'stencil then cover' paradigm by employing a state machine during the fragment shader stage of graphics pipeline.
A Virtual Reality Platform for Immersive Education in Computer Graphics
(The Eurographics Association, 2021) Hácha, Filip; Vanecek, Petr; Váša, Libor; Sousa Santos, Beatriz and Domik, Gitta
We present a general framework for teaching 3D imagination demanding topics using commonly available hardware for virtual reality (VR). Our software allows collaborating on 3D objects, interaction and annotation in a simple and intuitive manner. Students can follow the exposition from an arbitrary, naturally chosen point of view, and they interact with the shared scene by adding annotations and using a pointing metaphore. The software allows using various VR headsets as well as opting for a traditional 3D rendering on a 2D screen. The framework has been tested in a small course on polygon mesh processing, identifying and eliminating the most serious flaws. In its current form, most of the sources of friction have been addressed and the system can be employed in a variety of teaching scenarios.
Unsupervised Learning of Disentangled 3D Representation from a Single Image
(The Eurographics Association, 2021) Lv, Junliang; Jiang, Haiyong; Xiao, Jun; Bittner, Jirí and Waldner, Manuela
Learning 3D representation of a single image is challenging considering the ambiguity, occlusion, and perspective project of an object in an image. Previous works either seek image annotation or 3D supervision to learn meaningful factors of an object or employ a StyleGAN-like framework for image synthesis. While the first ones rely on tedious annotation and even dense geometry ground truth, the second solutions usually cannot guarantee consistency of shapes between different view images. In this paper, we combine the advantages of both frameworks and propose an image disentanglement method based on 3D representation. Results show our method facilitates unsupervised 3D representation learning while preserving consistency between images.
Ray Tracing Lossy Compressed Grid Primitives
(The Eurographics Association, 2021) Benthin, Carsten; Vaidyanathan, Karthik; Woop, Sven; Theisel, Holger and Wimmer, Michael
We propose a new watertight representation of geometry for ray tracing highly complex scenes in a memory efficient manner. Polygon meshes in the scene are first converted into compressed grid primitives, which are represented by a base bilinear patch with quantized displacement vectors. Ray-scene intersections are then computed by efficiently decompressing these grids onthe- fly and intersecting the implicit triangles. Our representation requires just 5:4??6:6 bytes per triangle for the combined geometry and acceleration structure, resulting in a 5-7x reduction in memory footprint compared to indexed triangle meshes. This is achieved with less than 15% increase in rendering time.
EUROGRAPHICS 2021: Tutorials Frontmatter
(Eurographics Association, 2021) O'Sullivan, Carol; Schmalstieg, Dieter; O'Sullivan, Carol and Schmalstieg, Dieter
Film Directing for Computer Games and Animation
(The Eurographics Association and John Wiley & Sons Ltd., 2021) Ronfard, Rémi; Bühler, Katja and Rushmeier, Holly
Over the last forty years, researchers in computer graphics have proposed a large variety of theoretical models and computer implementations of a virtual film director, capable of creating movies from minimal input such as a screenplay or storyboard. The underlying film directing techniques are also in high demand to assist and automate the generation of movies in computer games and animation. The goal of this survey is to characterize the spectrum of applications that require film directing, to present a historical and up-to-date summary of research in algorithmic film directing, and to identify promising avenues and hot topics for future research.
SoftWalks: Real-Time, Two-Ways Interaction between a Character and Loose Grounds
(The Eurographics Association, 2021) Paliard, Chloé; Alvarado, Eduardo; Rohmer, Damien; Cani, Marie-Paule; Theisel, Holger and Wimmer, Michael
When walking on loose terrains, possibly covered with vegetation, the ground and grass should deform, but the character's gait should also change accordingly.We propose a method for modeling such two-ways interactions in real-time.We first complement a layered character model by a high-level controller, which uses position and angular velocity inputs to improve dynamic oscillations when walking on various slopes. Secondly, at a refined level, the feet are set to locally deform the ground and surrounding vegetation using efficient procedural functions, while the character's response to such deformations is computed through adapted inverse kinematics. While simple to set up, our method is generic enough to adapt to any character morphology. Moreover, its ability to generate in real time, consistent gaits on a variety of loose grounds of arbitrary slope, possibly covered with grass, makes it an interesting solution to enhance films and games.

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