597 research outputs found
Ray Tracing in Non-Euclidean Spaces
This dissertation describes a method for modeling, simulating and real-time rendering piecewise linear approximations of generic non-Euclidean 3D spaces. The 3D rendering pipeline most commonly used, where one multiplies each vertex coordinate by a 4x4 matrix to project it on the screen does not work for all cases where the space does not obey Euclid’s postulates (non-Euclidean space). Furthermore, while other non-Euclidean rendering tools only work for a limited type of spaces, our approach allows us to model, simulate, and render any isometrically embeddable non-Euclidean space and eventual objects lying therein. We envision at least two main applications for our approach. The first for helping mathematicians get a better understanding of what arbitrary spaces look like (e.g., hyperconical space, hyper-spherical space, and so forth). The second for assisting physicists to visualize and simulate the effects of bent space (e.g., black holes, wormholes, Alcubierre drive, and so forth) on light, and on physical objectsEsta dissertação descreve um método para modelar, simular e renderizar aproximações
lineares de espaços não Euclideanos de forma genérica e em tempo real.
A técnica de renderização 3D mais comum, que multiplica a matriz de projeção 4 x
4 por cada vértice para determinar as coordenadas do respetivo pixel no ecrã, nem
sempre funciona quando o espaço não obedece a um postulado de Euclides (espaço
não-Euclideano).
Além disso, enquanto outras ferramentas para renderizar espaços não-Euclideanos só
funcionam para certos tipos de espaços, a nossa técnica permite modelar, simular e renderizar
qualquer espaço não-Euclideano embebível isometricamente, bem como eventuais
objetos nele existentes.
Antevemos pelo menos dois usos para a nossa técnica. A primeira para ajudar matemáticos
a compreender melhor o aspeto de espaços arbitrários (e.g., espaço hiper-cónico,
espaço hiper-esférico, etc.). A segunda para ajudar físicos a visualizar e simular os
efeitos de espaço curvo (e.g., buracos negros, buracos de minhoca, deformações Alcubierra
drive, etc.) em luz e objetos físicos circundantes
Ghost on the Shell: An Expressive Representation of General 3D Shapes
The creation of photorealistic virtual worlds requires the accurate modeling
of 3D surface geometry for a wide range of objects. For this, meshes are
appealing since they 1) enable fast physics-based rendering with realistic
material and lighting, 2) support physical simulation, and 3) are
memory-efficient for modern graphics pipelines. Recent work on reconstructing
and statistically modeling 3D shape, however, has critiqued meshes as being
topologically inflexible. To capture a wide range of object shapes, any 3D
representation must be able to model solid, watertight, shapes as well as thin,
open, surfaces. Recent work has focused on the former, and methods for
reconstructing open surfaces do not support fast reconstruction with material
and lighting or unconditional generative modelling. Inspired by the observation
that open surfaces can be seen as islands floating on watertight surfaces, we
parameterize open surfaces by defining a manifold signed distance field on
watertight templates. With this parameterization, we further develop a
grid-based and differentiable representation that parameterizes both watertight
and non-watertight meshes of arbitrary topology. Our new representation, called
Ghost-on-the-Shell (G-Shell), enables two important applications:
differentiable rasterization-based reconstruction from multiview images and
generative modelling of non-watertight meshes. We empirically demonstrate that
G-Shell achieves state-of-the-art performance on non-watertight mesh
reconstruction and generation tasks, while also performing effectively for
watertight meshes.Comment: Technical Report (26 pages, 16 figures, Project Page:
https://gshell3d.github.io/
Deep Shading: Convolutional Neural Networks for Screen-Space Shading
In computer vision, Convolutional Neural Networks (CNNs) have recently achieved new levels of performance for several inverse problems where RGB pixel appearance is mapped to attributes such as positions, normals or reflectance. In computer graphics, screen-space shading has recently increased the visual quality in interactive image synthesis, where per-pixel attributes such as positions, normals or reflectance of a virtual 3D scene are converted into RGB pixel appearance, enabling effects like ambient occlusion, indirect light, scattering, depth-of-field, motion blur, or anti-aliasing. In this paper we consider the diagonal problem: synthesizing appearance from given per-pixel attributes using a CNN. The resulting Deep Shading simulates all screen-space effects as well as arbitrary combinations thereof at competitive quality and speed while not being programmed by human experts but learned from example images
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 für die
Partikelmischung besser zu verstehen und zu überwachen, sollten nicht nur die Partikel selbst, sondern auch
spezielle von den Partikeln gebildete Bereiche, die den Simulationsfortschritt und die räumliche Verteilung
von Hotspots anzeigen können, visualisiert werden können. Dies sollte auch bei großen Packungen mit
Millionen von Partikeln zumindest mit einer interaktiven Darstellungsgeschwindigkeit möglich sein. . Da
die Simulation auf der Grafikkarte (GPU) durchgeführt wird, sollten die Visualisierungstechniken die Daten
des GPU-Speichers vollständig nutzen.
Um die Qualität von trockenen Partikelmischungen wie Beton zu verbessern, wurde der
Korngrößenverteilung große Aufmerksamkeit gewidmet, die die Raumfüllungsrate hauptsächlich
beeinflusst und daher zwei der wichtigsten Eigenschaften des Betons bestimmt: die strukturelle Robustheit
und die Haltbarkeit. Anhand der Korngrößenverteilung kann die Raumfüllungsrate durch
Computersimulationen bestimmt werden, die analytischen Ansätzen in der Praxis wegen der breiten
Größenverteilung der Partikel oft überlegen sind. Eine der weit verbreiteten Simulationsmethoden ist das
Collective Rearrangement, bei dem die Partikel zunächst an zufälligen Positionen innerhalb eines Behälters
platziert werden. Später werden Überlappungen zwischen Partikeln aufgelöst, indem überlappende Partikel
voneinander weggedrückt werden. Durch geschickte Anpassung der Behältergröße während 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 großen Menge von
Kugeln, bietet diese Dissertation zunächst schnelle und pixelgenaue Methoden zur neuartigen
Visualisierung der Überlappungen und Freiräume zwischen kugelförmigen Partikeln innerhalb eines
Behälters.. Die auf Rasterisierung basierenden Verfahren funktionieren gut für kleinere Partikelpackungen
bis ca. eine Million Kugeln. Bei größeren 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 für die
Simulation wiederverwenden und die zweite ist speichereffizienter. Beide BVHs nutzen die Idee des Loose
Octree und sind die ersten ihrer Art, die die Größe von Primitiven für interaktives Raytracing mit häufig
aktualisierten Beschleunigungsdatenstrukturen berücksichtigen. Darüber 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-sphärischer Partikel erweitert, bei denen
ein nicht-sphärisches Partikel durch ein starres System von Kugeln angenähert wird, um die vorhandene
kugelbasierte Simulation wiederverwenden zu können. Dazu wird auch eine neue GPU-basierte Methode
zum effizienten Füllen eines nicht-kugelförmigen Partikels mit polydispersen überlappenden Kugeln
vorgestellt, so dass ein Partikel mit weniger Kugeln gefüllt werden kann, ohne die Raumfüllungsrate zu
beeinträchtigen. Dies erleichtert sowohl die Simulation als auch die Visualisierung.
Basierend auf den Arbeiten in dieser Dissertation können ausgefeiltere Algorithmen entwickelt werden, um
großskalige nicht-sphärische 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 für die interaktive
Visualisierung anderer partikelbasierter Simulationen verwendet werden, bei denen spezielle Bereiche wie
Freiräume oder Überlappungen 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
Scalable Real-Time Rendering for Extremely Complex 3D Environments Using Multiple GPUs
In 3D visualization, real-time rendering of high-quality meshes in complex 3D environments is still one of the major challenges in computer graphics. New data acquisition techniques like 3D modeling and scanning have drastically increased the requirement for more complex models and the demand for higher display resolutions in recent years. Most of the existing acceleration techniques using a single GPU for rendering suffer from the limited GPU memory budget, the time-consuming sequential executions, and the finite display resolution. Recently, people have started building commodity workstations with multiple GPUs and multiple displays. As a result, more GPU memory is available across a distributed cluster of GPUs, more computational power is provided throughout the combination of multiple GPUs, and a higher display resolution can be achieved by connecting each GPU to a display monitor (resulting in a tiled large display configuration). However, using a multi-GPU workstation may not always give the desired rendering performance due to the imbalanced rendering workloads among GPUs and overheads caused by inter-GPU communication.
In this dissertation, I contribute a multi-GPU multi-display parallel rendering approach for complex 3D environments. The approach has the capability to support a high-performance and high-quality rendering of static and dynamic 3D environments. A novel parallel load balancing algorithm is developed based on a screen partitioning strategy to dynamically balance the number of vertices and triangles rendered by each GPU. The overhead of inter-GPU communication is minimized by transferring only a small amount of image pixels rather than chunks of 3D primitives with a novel frame exchanging algorithm. The state-of-the-art parallel mesh simplification and GPU out-of-core techniques are integrated into the multi-GPU multi-display system to accelerate the rendering process
Efficient From-Point Visibility for Global Illumination in Virtual Scenes with Participating Media
Sichtbarkeitsbestimmung ist einer der fundamentalen Bausteine fotorealistischer Bildsynthese. Da die Berechnung der Sichtbarkeit allerdings äußerst kostspielig zu berechnen ist, wird nahezu die gesamte Berechnungszeit darauf verwendet. In dieser Arbeit stellen wir neue Methoden zur Speicherung, Berechnung und Approximation von Sichtbarkeit in Szenen mit streuenden Medien vor, die die Berechnung erheblich beschleunigen, dabei trotzdem qualitativ hochwertige und artefaktfreie Ergebnisse liefern
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