64 research outputs found
Visualization and inspection of the geometry of particle packings
Gegenstand dieser Dissertation ist die Entwicklung von effizienten Verfahren zur Visualisierung und
Inspektion der Geometrie von Partikelmischungen. Um das Verhalten der Simulation fĂŒr die
Partikelmischung besser zu verstehen und zu ĂŒberwachen, sollten nicht nur die Partikel selbst, sondern auch
spezielle von den Partikeln gebildete Bereiche, die den Simulationsfortschritt und die rÀumliche Verteilung
von Hotspots anzeigen können, visualisiert werden können. Dies sollte auch bei groĂen Packungen mit
Millionen von Partikeln zumindest mit einer interaktiven Darstellungsgeschwindigkeit möglich sein. . Da
die Simulation auf der Grafikkarte (GPU) durchgefĂŒhrt wird, sollten die Visualisierungstechniken die Daten
des GPU-Speichers vollstÀndig nutzen.
Um die QualitÀt von trockenen Partikelmischungen wie Beton zu verbessern, wurde der
KorngröĂenverteilung groĂe Aufmerksamkeit gewidmet, die die RaumfĂŒllungsrate hauptsĂ€chlich
beeinflusst und daher zwei der wichtigsten Eigenschaften des Betons bestimmt: die strukturelle Robustheit
und die Haltbarkeit. Anhand der KorngröĂenverteilung kann die RaumfĂŒllungsrate durch
Computersimulationen bestimmt werden, die analytischen AnsÀtzen in der Praxis wegen der breiten
GröĂenverteilung der Partikel oft ĂŒberlegen sind. Eine der weit verbreiteten Simulationsmethoden ist das
Collective Rearrangement, bei dem die Partikel zunÀchst an zufÀlligen Positionen innerhalb eines BehÀlters
platziert werden. SpĂ€ter werden Ăberlappungen zwischen Partikeln aufgelöst, indem ĂŒberlappende Partikel
voneinander weggedrĂŒckt werden. Durch geschickte Anpassung der BehĂ€ltergröĂe wĂ€hrend der Simulation,
kann die Collective Rearrangement-Methode am Ende eine ziemlich dichte Partikelpackung generieren.
Es ist jedoch sehr schwierig, den gesamten Simulationsprozess ohne ein interaktives Visualisierungstool zu
optimieren oder dort Fehler zu finden.
Ausgehend von der etablierten rasterisierungsbasierten Methode zum Darstellen einer groĂen Menge von
Kugeln, bietet diese Dissertation zunÀchst schnelle und pixelgenaue Methoden zur neuartigen
Visualisierung der Ăberlappungen und FreirĂ€ume zwischen kugelförmigen Partikeln innerhalb eines
BehĂ€lters.. Die auf Rasterisierung basierenden Verfahren funktionieren gut fĂŒr kleinere Partikelpackungen
bis ca. eine Million Kugeln. Bei gröĂeren Packungen entstehen Probleme durch die lineare Laufzeit und
den Speicherverbrauch. Zur Lösung dieses Problems werden neue Methoden mit Hilfe von Raytracing
zusammen mit zwei neuen Arten von Bounding-Volume-Hierarchien (BVHs) bereitgestellt. Diese können
den Raytracing-Prozess deutlich beschleunigen --- die erste kann die vorhandene Datenstruktur fĂŒr die
Simulation wiederverwenden und die zweite ist speichereffizienter. Beide BVHs nutzen die Idee des Loose
Octree und sind die ersten ihrer Art, die die GröĂe von Primitiven fĂŒr interaktives Raytracing mit hĂ€ufig
aktualisierten Beschleunigungsdatenstrukturen berĂŒcksichtigen. DarĂŒber hinaus können die
Visualisierungstechniken in dieser Dissertation auch angepasst werden, um Eigenschaften wie das
Volumen bestimmter Bereiche zu berechnen.
All diese Visualisierungstechniken werden dann auf den Fall nicht-sphÀrischer Partikel erweitert, bei denen
ein nicht-sphÀrisches Partikel durch ein starres System von Kugeln angenÀhert wird, um die vorhandene
kugelbasierte Simulation wiederverwenden zu können. Dazu wird auch eine neue GPU-basierte Methode
zum effizienten FĂŒllen eines nicht-kugelförmigen Partikels mit polydispersen ĂŒberlappenden Kugeln
vorgestellt, so dass ein Partikel mit weniger Kugeln gefĂŒllt werden kann, ohne die RaumfĂŒllungsrate zu
beeintrÀchtigen. Dies erleichtert sowohl die Simulation als auch die Visualisierung.
Basierend auf den Arbeiten in dieser Dissertation können ausgefeiltere Algorithmen entwickelt werden, um
groĂskalige nicht-sphĂ€rische Partikelmischungen effizienter zu visualisieren. Weiterhin kann in Zukunft
Hardware-Raytracing neuerer Grafikkarten anstelle des in dieser Dissertation eingesetzten Software-Raytracing verwendet werden. Die neuen Techniken können auch als Grundlage fĂŒr die interaktive
Visualisierung anderer partikelbasierter Simulationen verwendet werden, bei denen spezielle Bereiche wie
FreirĂ€ume oder Ăberlappungen zwischen Partikeln relevant sind.The aim of this dissertation is to find efficient techniques for visualizing and inspecting the geometry of
particle packings. Simulations of such packings are used e.g. in material sciences to predict properties of
granular materials. To better understand and supervise the behavior of these simulations, not only the
particles themselves but also special areas formed by the particles that can show the progress of the
simulation and spatial distribution of hot spots, should be visualized. This should be possible with a frame
rate that allows interaction even for large scale packings with millions of particles. Moreover, given the
simulation is conducted in the GPU, the visualization techniques should take full use of the data in the GPU
memory.
To improve the performance of granular materials like concrete, considerable attention has been paid to the
particle size distribution, which is the main determinant for the space filling rate and therefore affects two
of the most important properties of the concrete: the structural robustness and the durability. Given the
particle size distribution, the space filling rate can be determined by computer simulations, which are often
superior to analytical approaches due to irregularities of particles and the wide range of size distribution in
practice. One of the widely adopted simulation methods is the collective rearrangement, for which particles
are first placed at random positions inside a container, later overlaps between particles will be resolved by
letting overlapped particles push away from each other to fill empty space in the container. By cleverly
adjusting the size of the container according to the process of the simulation, the collective rearrangement
method could get a pretty dense particle packing in the end. However, it is very hard to fine-tune or debug
the whole simulation process without an interactive visualization tool.
Starting from the well-established rasterization-based method to render spheres, this dissertation first
provides new fast and pixel-accurate methods to visualize the overlaps and free spaces between spherical
particles inside a container. The rasterization-based techniques perform well for small scale particle
packings but deteriorate for large scale packings due to the large memory requirements that are hard to be
approximated correctly in advance. To address this problem, new methods based on ray tracing are provided
along with two new kinds of bounding volume hierarchies (BVHs) to accelerate the ray tracing process ---
the first one can reuse the existing data structure for simulation and the second one is more memory efficient.
Both BVHs utilize the idea of loose octree and are the first of their kind to consider the size of primitives
for interactive ray tracing with frequently updated acceleration structures. Moreover, the visualization
techniques provided in this dissertation can also be adjusted to calculate properties such as volumes of the
specific areas.
All these visualization techniques are then extended to non-spherical particles, where a non-spherical
particle is approximated by a rigid system of spheres to reuse the existing simulation. To this end a new
GPU-based method is presented to fill a non-spherical particle with polydisperse possibly overlapping
spheres efficiently, so that a particle can be filled with fewer spheres without sacrificing the space filling
rate. This eases both simulation and visualization.
Based on approaches presented in this dissertation, more sophisticated algorithms can be developed to
visualize large scale non-spherical particle mixtures more efficiently. Besides, one can try to exploit the
hardware ray tracing of more recent graphic cards instead of maintaining the software ray tracing as in this
dissertation. The new techniques can also become the basis for interactively visualizing other particle-based
simulations, where special areas such as free space or overlaps between particles are of interest
Ray Tracing Gems
This book is a must-have for anyone serious about rendering in real time. With the announcement of new ray tracing APIs and hardware to support them, developers can easily create real-time applications with ray tracing as a core component. As ray tracing on the GPU becomes faster, it will play a more central role in real-time rendering. Ray Tracing Gems provides key building blocks for developers of games, architectural applications, visualizations, and more. Experts in rendering share their knowledge by explaining everything from nitty-gritty techniques that will improve any ray tracer to mastery of the new capabilities of current and future hardware. What you'll learn: The latest ray tracing techniques for developing real-time applications in multiple domains Guidance, advice, and best practices for rendering applications with Microsoft DirectX Raytracing (DXR) How to implement high-performance graphics for interactive visualizations, games, simulations, and more Who this book is for: Developers who are looking to leverage the latest APIs and GPU technology for real-time rendering and ray tracing Students looking to learn about best practices in these areas Enthusiasts who want to understand and experiment with their new GPU
Volumetric particle modeling
This dissertation presents a robust method of modeling objects and forces for computer animation. Within
this method objects and forces are represented as particles. As in most modeling systems, the movement of
objects is driven by physically based forces. The usage of particles, however, allows more artistically
motivated behavior to be achieved and also allows the modeling of heterogeneous objects and objects in
different state phases: solid, liquid or gas. By using invisible particles to propagate forces through the
modeling environment complex behavior is achieved through the interaction of relatively simple
components. In sum, 'macroscopic' behavior emerges from 'microscopic' modeling.
We present a newly developed modeling framework expanding on related work. This framework allows
objects and forces to be modeled using particle representations and provides the details on how objects are
created, how they interact, and how they may be displayed. We present examples to demonstrate the
viability and robustness of the developed method of modeling. They illustrate the breaking and fracturing
of solids, the interaction of objects in different phase states, and the achievement of a reasonable balance
between artistic and physically based behaviors
Towards realistic interactive sand : a GPU-based framework
Includes bibliographical references (leaves 147-160).Many real-time computer games contain virtual worlds built upon terrestrial landscapes, in particular, "sandy" terrains, such as deserts and beaches. These terrains often contain large quantities of granular material, including sand, soil, rubble, and gravel. Allowing other environmental elements, such as trees or bodies of water, as well as players, to interact naturally and realistically with sand, is an important milestone for achieving realism in games. In the past, game developers have resorted to approximating sand with flat. textured surfaces that are static, non-granular, and do not behave like the physical material they model. A reasonable expectation is that sand be granular in its composition and governed by the laws of physics in its behaviour. However, for a single PC user, physics-based models are too computationally expensive to simulate and animate in real-time. An alternative is to use computer clusters to handle numerically intensive simulation, but at the loss of single-user affordability and real-time interactivity. Instead, we propose a GPU-based simulation framework that exploits the massive computational parallelism of a modern GPU to achieve interactive frame rates, on a single PC. We base our method on a discrete elements approach that represents each sand granule as a rigid arrangement of particles. Our model shows highly dynamic phenomena, such as splashing and avalanching, as well as static dune formation. Moreover, by utilising standard metrics taken from granular material science, we show that the simulated sand behaves in accordance with previous numerical and experimental research. We also support general rigid bodies in the simulation by automated particle-based sampling of their surfaces. This allows sand to interact naturally with its environment without extensive modification to underlying physics engine. The generality of our physics framework also allows for real-time physically-based rigid body simulation sans sand, as demonstrated in our testing. Finally, we describe an accelerated real-time method for lighting sand that supports both self-shadowing and environmental shadowing effects
Literatures of Stress: Thermodynamic Physics and the Poetry and Prose of Gerard Manley Hopkins
This dissertation examines two of the various literatures of energy in Victorian Britain: the scientific literature of the North British school of energy physics, and the poetic and prose literature of Gerard Manley Hopkins. As an interdisciplinary effort, it is intended for several audiences. For readers interested in science history, it offers a history of two terms â stress and strain â central to modern physics. As well, in discussing the ideas of various scientific authors (primarily William John Macquorn Rankine, William Thomson, P.G. Tait, and James Clerk Maxwell), it indicates several contributions these figures made to larger culture.
For readers of Hopkinsâ poems and prose, this dissertation corresponds with a recent trend in criticism in its estimation of Hopkins as a scientifically informed writer, at least in his years post-Stonyhurst. Accordingly, this dissertation presents readings of Hopkinsâ poetry and prose in light of developments in Victorian energy physics. Three claims span the chapters pertaining to Hopkinsâ oeuvre: First, that Hopkinsâ distinctive terminology of stress and instress expresses the energetic relations between objects. Second, that Hopkinsâ metaphors and analogies are unusual in that they often signify literal relationships between things compared, particularly when metaphysical forms of stress or instress are likened to physical forms of energy. And third, that in Hopkinsâ writings the natural world and the supernatural order of creation are contiguous, and that energy suffuses both
A starting guide to root ecology: strengthening ecological concepts and standardising root classification, sampling, processing and trait measurements
In the context of a recent massive increase in research on plant root functions and their impact on the environment, root ecologists currently face many important challenges to keep on generating cutting-edge, meaningful and integrated knowledge. Consideration of the below-ground components in plant and ecosystem studies has been consistently called for in recent decades, but methodology is disparate and sometimes inappropriate. This handbook, based on the collective effort of a large team of experts, will improve trait comparisons across studies and integration of information across databases by providing standardised methods and controlled vocabularies. It is meant to be used not only as starting point by students and scientists who desire working on below-ground ecosystems, but also by experts for consolidating and broadening their views on multiple aspects of root ecology. Beyond the classical compilation of measurement protocols, we have synthesised recommendations from the literature to provide key background knowledge useful for: (1) defining below-ground plant entities and giving keys for their meaningful dissection, classification and naming beyond the classical fine-root vs coarse-root approach; (2) considering the specificity of root research to produce sound laboratory and field data; (3) describing typical, but overlooked steps for studying roots (e.g. root handling, cleaning and storage); and (4) gathering metadata necessary for the interpretation of results and their reuse. Most importantly, all root traits have been introduced with some degree of ecological context that will be a foundation for understanding their ecological meaning, their typical use and uncertainties, and some methodological and conceptual perspectives for future research. Considering all of this, we urge readers not to solely extract protocol recommendations for trait measurements from this work, but to take a moment to read and reflect on the extensive information contained in this broader guide to root ecology, including sections IâVII and the many introductions to each section and root trait description. Finally, it is critical to understand that a major aim of this guide is to help break down barriers between the many subdisciplines of root ecology and ecophysiology, broaden researchersâ views on the multiple aspects of root study and create favourable conditions for the inception of comprehensive experiments on the role of roots in plant and ecosystem functioning
Handbook of the Cultural Foundations of Learning
Edited by a diverse group of expert collaborators, the Handbook of the Cultural Foundations of Learning is a landmark volume that brings together cutting-edge research examining learning as entailing inherently cultural processes. Conceptualizing culture as both a set of social practices and connected to learner identities, the chapters synthesize contemporary research in elaborating a new vision of the cultural nature of learning, moving beyond summary to reshape the field toward studies that situate culture in the learning sciences alongside equity of educational processes and outcomes. With the recent increased focus on culture and equity within the educational research community, this volume presents a comprehensive, innovative treatment of what has become one of the fieldâs most timely and relevant topics
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