EG2021

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

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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.
Auto-rigging 3D Bipedal Characters in Arbitrary Poses
(The Eurographics Association, 2021) Kim, Jeonghwan; Son, Hyeontae; Bae, Jinseok; Kim, Young Min; Theisel, Holger and Wimmer, Michael
We present an end-to-end algorithm that can automatically rig a given 3D character such that it is ready for 3D animation. The animation of a virtual character requires the skeletal motion defined with bones and joints, and the corresponding deformation of the mesh represented with skin weights. While the conventional animation pipeline requires the initial 3D character to be in the predefined default pose, our pipeline can rig a 3D character in arbitrary pose. We handle the increased ambiguity by fixing the skeletal topology and solving for the full deformation space. After the skeletal positions and orientations are fully discovered, we can deform the provided 3D character into the default pose, from which we can animate the character with the help of recent motion-retargeting techniques. Our results show that we can successfully animate initially deformed characters, which was not possible with previous works.
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.
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.
Fast and Robust Registration and Calibration of Depth-Only Sensors
(The Eurographics Association, 2021) Mühlenbrock, Andre; Fischer, Roland; Weller, René; Zachmann, Gabriel; Bittner, Jirí and Waldner, Manuela
The precise registration between multiple depth cameras is a crucial prerequisite for many applications. Previous techniques frequently rely on RGB or IR images and checkerboard targets for feature detection, partly due to the depth data being inherently noisy. This limitation prohibits the usage for use-cases where neither is available. We present a novel registration approach that solely uses depth data for feature detection, making it more universally applicable while still achieving robust and precise results. We propose a combination of a custom 3D registration target - a lattice with regularly-spaced holes - and a feature detection algorithm that is able to reliably extract the lattice and its features from noisy depth images.
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.
Generative Landmarks
(The Eurographics Association, 2021) Ferman, David; Bharaj, Gaurav; Bittner, Jirí and Waldner, Manuela
We propose a general purpose approach to detect landmarks with improved temporal consistency, and personalization. Most sparse landmark detection methods rely on laborious, manually labelled landmarks, where inconsistency in annotations over a temporal volume leads to sub-optimal landmark learning. Further, high-quality landmarks with personalization is often hard to achieve. We pose landmark detection as an image translation problem. We capture two sets of unpaired marked (with paint) and unmarked videos. We then use a generative adversarial network and cyclic consistency to predict deformations of landmark templates that simulate markers on unmarked images until these images are indistinguishable from ground-truth marked images. Our novel method does not rely on manually labelled priors, is temporally consistent, and image class agnostic - face, and hand landmarks detection examples are shown.
Illumination-driven Light Probe Placement
(The Eurographics Association, 2021) Vardis, Konstantinos; Vasilakis, Andreas Alexandros; Papaioannou, Georgios; Bittner, Jirí and Waldner, Manuela
We introduce a simplification method for light probe configurations that preserves the indirect illumination distribution in scenes with diverse lighting conditions. An iterative graph simplification algorithm discards the probes that, according to a set of evaluation points, have the least impact on the global light field. Our approach is simple, generic and aims at improving the repetitive and often non-intuitive and tedious task of placing light probes on complex virtual environments.
Interactive Finite Element Model of Needle Insertion and Laceration
(The Eurographics Association, 2021) Perrusi, Pedro Henrique Suruagy; Baksic, Paul; Courtecuisse, Hadrien; Theisel, Holger and Wimmer, Michael
This paper introduces an interactive model of needle insertion, including the possibility to simulate lacerations of tissue around the needle. The method relies on complementary constraints to couple the Finite Element models of the needle and tissue. The cutting path is generated from mechanical criteria (i.e. cutting force) at arbitrary resolution, avoiding expensive remeshing of Finite Element meshes. Complex behavior can be simulated in real time such as friction along the shaft of the needle, puncture and cutting force resulting from interactions of the needle with the tissue. The method is illustrated both in an interactive simulation of a needle insertion/cutting and in a robotic needle insertion in liver tissue during the breathing motion.
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.
Interactive Synthesis of 3D Geometries of Blood Vessels
(The Eurographics Association, 2021) Rauch, Nikolaus; Harders, Matthias; Theisel, Holger and Wimmer, Michael
In surgical training simulators, where various organ surfaces make up the majority of the scene, the visual appearance is highly dependent on the quality of the surface textures. Blood vessels are an important detail in this; they need to be incorporated into an organ's texture. Moreover, the actual blood vessel geometries also have to be part of the simulated surgical procedure itself, e.g. during cutting. Since the manual creation of vessel geometry or branching details on textures is highly tedious, an automatic synthesis technique capable of generating a wide range of blood vessel patterns is needed.We propose a new synthesis approach based on the space colonization algorithm. As extension, physiological constraints on the proliferation of branches are enforced to create realistic vascular structures. Our framework is capable of generating three-dimensional blood vessel networks in a matter of milliseconds, thus allowing a 3D modeller to tweak parameters in real-time to obtain a desired appearance.
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.
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.
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.
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.
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.
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.
A Survey on Bounding Volume Hierarchies for Ray Tracing
(The Eurographics Association and John Wiley & Sons Ltd., 2021) Meister, Daniel; Ogaki, Shinji; Benthin, Carsten; Doyle, Michael J.; Guthe, Michael; Bittner, Jirí; Bühler, Katja and Rushmeier, Holly
Ray tracing is an inherent part of photorealistic image synthesis algorithms. The problem of ray tracing is to find the nearest intersection with a given ray and scene. Although this geometric operation is relatively simple, in practice, we have to evaluate billions of such operations as the scene consists of millions of primitives, and the image synthesis algorithms require a high number of samples to provide a plausible result. Thus, scene primitives are commonly arranged in spatial data structures to accelerate the search. In the last two decades, the bounding volume hierarchy (BVH) has become the de facto standard acceleration data structure for ray tracing-based rendering algorithms in offline and recently also in real-time applications. In this report, we review the basic principles of bounding volume hierarchies as well as advanced state of the art methods with a focus on the construction and traversal. Furthermore, we discuss industrial frameworks, specialized hardware architectures, other applications of bounding volume hierarchies, best practices, and related open problems.
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.

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Browsing EG2021 by Subject "Computing methodologies"

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