EG2021

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

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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.
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.
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.
Interactive Simulation for easy Decision-making in Fluid Dynamics
(The Eurographics Association, 2021) Wang, Mengchen; Férey, Nicolas; Magoulès, Frédéric; Bourdot, Patrick; Theisel, Holger and Wimmer, Michael
A conventional study of fluid simulation involves different stages including conception, simulation, visualization, and analysis tasks. It is, therefore, necessary to switch between different software and interactive contexts which implies costly data manipulation and increases the time needed for decision making. Our interactive simulation approach was designed to shorten this loop, allowing users to visualize and steer a simulation in progress without waiting for the end of the simulation. The methodology allows the users to control, start, pause, or stop a simulation in progress, to change global physical parameters, to interact with its 3D environment by editing boundary conditions such as walls or obstacles. This approach is made possible by using a methodology such as the Lattice Boltzmann Method (LBM) to achieve interactive time while remaining physically relevant. In this work, we present our platform dedicated to interactive fluid simulation based on LBM. The contribution of our interactive simulation approach to decision making will be evaluated in a study based on a simple but realistic use case.
Robust Image Denoising using Kernel Predicting Networks
(The Eurographics Association, 2021) Cai, Zhilin; Zhang, Yang; Manzi, Marco; Oztireli, Cengiz; Gross, Markus; Aydin, Tunç Ozan; Theisel, Holger and Wimmer, Michael
We present a new method for designing high quality denoisers that are robust to varying noise characteristics of input images. Instead of taking a conventional blind denoising approach or relying on explicit noise parameter estimation networks as well as invertible camera imaging pipeline models, we propose a two-stage model that first processes an input image with a small set of specialized denoisers, and then passes the resulting intermediate denoised images to a kernel predicting network that estimates per-pixel denoising kernels. We demonstrate that our approach achieves robustness to noise parameters at a level that exceeds comparable blind denoisers, while also coming close to state-of-the-art denoising quality for camera sensor noise.
Data-driven Garment Pattern Estimation from 3D Geometries
(The Eurographics Association, 2021) Goto, Chihiro; Umetani, Nobuyuki; Theisel, Holger and Wimmer, Michael
Three-dimensional scanning technology recently becomes widely available to the public. However, it is difficult to simulate clothing deformation from the scanned people because scanned data lacks information required for the clothing simulation. In this paper, we present a technique to estimate clothing patterns from a scanned person in cloth. Our technique uses image-based deep learning to estimate the type of pattern on the projected image. The key contribution is converting image-based inference into three-dimensional clothing pattern estimation. We evaluate our technique by applying our technique to an actual scan.
State of the Art on Computational Design of Assemblies with Rigid Parts
(The Eurographics Association and John Wiley & Sons Ltd., 2021) Wang, Ziqi; Song, Peng; Pauly, Mark; Bühler, Katja and Rushmeier, Holly
An assembly refers to a collection of parts joined together to achieve a specific form and/or functionality. Designing assemblies is a non-trivial task as a slight local modification on a part's geometry or its joining method could have a global impact on the structural and/or functional performance of the whole assembly. Assemblies can be classified as structures that transmit force to carry loads and mechanisms that transfer motion and force to perform mechanical work. In this state-of-the-art report, we focus on computational design of structures with rigid parts, which generally can be formulated as a geometric modeling and optimization problem. We broadly classify existing computational design approaches, mainly from the computer graphics community, according to high-level design objectives, including fabricability, structural stability, reconfigurability, and tileability. Computational analysis of various aspects of assemblies is an integral component in these design approaches. We review different classes of computational analysis and design methods, discuss their strengths and limitations, make connections among them, and propose possible directions for future research.
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.
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.
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: Posters Frontmatter
(Eurographics Association, 2021) Bittner, Jirí; Waldner, Manuela; Bittner, Jirí and Waldner, Manuela
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.
EUROGRAPHICS 2021: Tutorials Frontmatter
(Eurographics Association, 2021) O'Sullivan, Carol; Schmalstieg, Dieter; O'Sullivan, Carol and Schmalstieg, Dieter
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.
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.
Tight Normal Cone Merging for Efficient Collision Detection of Thin Deformable Objects
(The Eurographics Association, 2021) Han, Dong-Hoon; Lee, Chang-Jin; Lee, Sangbin; Ko, Hyeong-Seok; Theisel, Holger and Wimmer, Michael
When simulating thin deformable objects such as clothes, collision detection alone takes a lot of computation. One way of reducing the computation is culling false-positives as much as possible. In the context of bounding volume hierarchy, Provot proposed a culling method that is based on hierarchical merging of normal enclosing cones. In this work, we investigate Provot's merging algorithm and show that there is some room for improvement. We propose a new merging algorithm, in the context of discrete collision detection, which always produces an equal or tighter mergence than Provot's merging. We extend the above algorithm so that it can be used in the context of continuous collision detection. Experiments show that the proposed method makes about 25% reduction in the number of triangle pairs for which vertex-triangle or edge-edge collision test has to be performed, and 18% reduction in time for collision detection.
Teaching Data-driven Video Processing via Crowdsourced Data Collection
(The Eurographics Association, 2021) Reimann, Max; Wegen, Ole; Pasewaldt, Sebastian; Semmo, Amir; Döllner, Jürgen; Trapp, Matthias; Sousa Santos, Beatriz and Domik, Gitta
This paper presents the concept and experience of teaching an undergraduate course on data-driven image and video processing. When designing visual effects that make use of Machine Learning (ML) models for image-based analysis or processing, the availability of training data typically represents a key limitation when it comes to feasibility and effect quality. The goal of our course is to enable students to implement new kinds of visual effects by acquiring training datasets via crowdsourcing that are used to train ML models as part of a video processing pipeline. First, we propose our course structure and best practices that are involved with crowdsourced data acquisitions. We then discuss the key insights we gathered from an exceptional undergraduate seminar project that tackles the challenging domain of video annotation and learning. In particular, we focus on how to practically develop annotation tools and collect high-quality datasets using Amazon Mechanical Turk (MTurk) in the budget- and time-constrained classroom environment. We observe that implementing the full acquisition and learning pipeline is entirely feasible for a seminar project, imparts hands-on problem solving skills, and promotes undergraduate 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.
Reconstructing the Past: Outstanding Student-Created Virtual Heritage Experiences
(The Eurographics Association, 2021) Anderson, Eike Falk; Sousa Santos, Beatriz and Domik, Gitta
In recent years, Computer Graphics (CG) and related techniques have become increasingly important for the preservation and dissemination of Cultural Heritage (CH). Here we present a set of three excellent CH reconstructions and virtual heritage experiences created by final year undergraduate students from several computer animation related programmes of study in the course of an optional course on ''CG and Animation for Cultural Heritage''. The three projects discussed here are interactive heritage experiences, including a reconstruction of the tomb of Tutankhamun, an Augmented Reality (AR) reconstruction of the Iron Age hillfort Maiden Castle, and a Virtual Reality (VR) reconstruction of ancient Stonehenge.

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