66 research outputs found
Volumetric cloud generation using a Chinese brush calligraphy style
Includes bibliographical references.Clouds are an important feature of any real or simulated environment in which the sky is visible. Their amorphous, ever-changing and illuminated features make the sky vivid and beautiful. However, these features increase both the complexity of real time rendering and modelling. It is difficult to design and build volumetric clouds in an easy and intuitive way, particularly if the interface is intended for artists rather than programmers. We propose a novel modelling system motivated by an ancient painting style, Chinese Landscape Painting, to address this problem. With the use of only one brush and one colour, an artist can paint a vivid and detailed landscape efficiently. In this research, we develop three emulations of a Chinese brush: a skeleton-based brush, a 2D texture footprint and a dynamic 3D footprint, all driven by the motion and pressure of a stylus pen. We propose a hybrid mapping to generate both the body and surface of volumetric clouds from the brush footprints. Our interface integrates these components along with 3D canvas control and GPU-based volumetric rendering into an interactive cloud modelling system. Our cloud modelling system is able to create various types of clouds occurring in nature. User tests indicate that our brush calligraphy approach is preferred to conventional volumetric cloud modelling and that it produces convincing 3D cloud formations in an intuitive and interactive fashion. While traditional modelling systems focus on surface generation of 3D objects, our brush calligraphy technique constructs the interior structure. This forms the basis of a new modelling style for objects with amorphous shape
Fast Reliable Ray-tracing of Procedurally Defined Implicit Surfaces Using Revised Affine Arithmetic
Fast and reliable rendering of implicit surfaces is an important area in the field of implicit modelling. Direct rendering, namely ray-tracing, is shown to be a suitable technique for obtaining good-quality visualisations of implicit surfaces. We present a technique for reliable ray-tracing of arbitrary procedurally defined implicit surfaces by using a modification of Affine Arithmetic called Revised Affine Arithmetic. A wide range of procedurally defined implicit objects can be rendered using this technique including polynomial surfaces, constructive solids, pseudo-random objects, procedurally defined microstructures, and others. We compare our technique with other reliable techniques based on Interval and Affine Arithmetic to show that our technique provides the fastest, while still reliable, ray-surface intersections and ray-tracing. We also suggest possible modifications for the GPU implementation of this technique for real-time rendering of relatively simple implicit models and for near real-time for complex implicit models
Stochastic Volume Rendering of Multi-Phase SPH Data
In this paper, we present a novel method for the direct volume rendering of large smoothedâparticle hydrodynamics (SPH) simulation data without transforming the unstructured data to an intermediate representation. By directly visualizing the unstructured particle data, we avoid long preprocessing times and large storage requirements. This enables the visualization of large, timeâdependent, and multivariate data both as a postâprocess and in situ. To address the computational complexity, we introduce stochastic volume rendering that considers only a subset of particles at each step during ray marching. The sample probabilities for selecting this subset at each step are thereby determined both in a viewâdependent manner and based on the spatial complexity of the data. Our stochastic volume rendering enables us to scale continuously from a fast, interactive preview to a more accurate volume rendering at higher cost. Lastly, we discuss the visualization of freeâsurface and multiâphase flows by including a multiâmaterial model with volumetric and surface shading into the stochastic volume rendering
A Render Model For Particle System
Particle system is a very commonly used system in computer graphics. It can be used to simulate
many objects in the real world, such as liquid simulation, smoke simulation and so on. Now, a
new method called welding simulation has been developed. In this simulation, it needs to give the
particle system a metal-like surface. Therefore, in this thesis, we developed a render model which
can make a particle system have a metal-like surface. This render model can be used in welding
simulation application and also for other applications based on particle systems with metal-like
surfac
Fast reliable interrogation of procedurally defined implicit surfaces using extended revised affine arithmetic.
Techniques based on interval and previous termaffine arithmetic next term and their modifications are shown to provide previous term reliable next term function range evaluation for the purposes of previous termsurface interrogation.next term In this paper we present a technique for the previous termreliable interrogation of implicit surfacesnext term using a modification of previous termaffine arithmeticnext term called previous term revised affine arithmetic.next term We extend the range of functions presented in previous termrevised affine arithmeticnext term by introducing previous termaffinenext term operations for arbitrary functions such as set-theoretic operations with R-functions, blending and conditional operators. The obtained previous termaffinenext term forms of arbitrary functions provide previous termfasternext term and tighter function range evaluation. Several case studies for operations using previous termaffinenext term forms are presented. The proposed techniques for previous termsurface interrogationnext term are tested using ray-previous termsurfacenext term intersection for ray-tracing and spatial cell enumeration for polygonisation. These applications with our extensions provide previous termfast and reliablenext term rendering of a wide range of arbitrary previous termprocedurally defined implicit surfacesnext term (including polynomial previous termsurfaces,next term constructive solids, pseudo-random objects, previous termprocedurally definednext term microstructures, and others). We compare the function range evaluation technique based on previous termextended revised affine arithmeticnext term with other previous termreliablenext term techniques based on interval and previous termaffine arithmeticnext term to show that our technique provides the previous termfastestnext term and tightest function range evaluation for previous termfast and reliable interrogation of procedurally defined implicit surfaces.next term
Research Highlights
The main contributions of this paper are as follows. âș The widening of the scope of previous termreliablenext term ray-tracing and spatial enumeration algorithms for previous termsurfacesnext term ranging from algebraic previous termsurfaces (definednext term by polynomials) to general previous termimplicit surfaces (definednext term by function evaluation procedures involving both previous termaffinenext term and non-previous termaffinenext term operations based on previous termrevised affine arithmetic)next term. âș The introduction of a technique for representing procedural models using special previous termaffinenext term forms (illustrated by case studies of previous termaffinenext term forms for set-theoretic operations in the form of R-functions, blending operations and conditional operations). âș The detailed derivation of special previous termaffinenext term forms for arbitrary operators
Image-based Control and Automation of High-speed X-ray Imaging Experiments
Moderne Röntgenbildgebung gibt Aufschluss ĂŒber die innere Struktur von Objekten aus den verschiedensten Materialien. Der Erfolg solcher Messungen hĂ€ngt dabei entscheidend von einer geeigneten Wahl der Aufnahmebedingungen ab, von der mechanischen Instrumentierung und von den Eigenschaften der Probe oder des untersuchten Prozesses selbst. Bisher gibt es kein bekanntes Verfahren fĂŒr autonome Datenakquise, welches auch fĂŒr sehr verschiedene Röntgenbildgebungsexperimenten die Steuerung ĂŒber bildbasiertes Feedback erlaubt. Die vorliegende Arbeit setzt sich als Ziel, diese LĂŒcke zu schlieĂen, indem gezielt die hierbei auftretenden Probleme angegangen und gelöst werden: die Auswahl der experimentellen Startparameter, eine schnelle Verarbeitung der aufgenommenen Daten und ein automatisches Feedback zur Korrektur der laufenden Messprozedur.
Um die am besten geeigneten experimentellen Bedingungen zu bestimmen, gehen wir von den Grundlagen der Bildentstehung aus und entwickeln ein Framework fĂŒr dessen Simulation. Dieses ermöglicht uns eine groĂe Bandbreite an virtuellen Röntgenbildgebungsexperimenten durchzufĂŒhren, wobei die entscheidenden physikalischen Prozesse auf dem Weg der Röntgenstrahlung von der Quelle bis zum Detektor berĂŒcksichtigt werden. DarĂŒber hinaus betrachten wir verschiedene Probenformen und bewegungen, was uns die Simulation von Experimenten wie etwa 4D (zeitaufgelöster) Tomographie ermöglicht.
AuĂerdem entwickeln wir eine autonome Prozedur fĂŒr die Datenakquise, welches die Startbedingungen des Versuchs dann wĂ€hrend der schon laufenden Messung auf Basis schneller Bildanalyse das nachjustiert und auch andere Parameter des Experiments steuern kann. Besonderes Augenmerk legen wir hier auf Hochgeschwindigkeitsexperimente, welche hohen Anforderungen an die Geschwindigkeit der Datenverarbeitung stellen, vor allem wenn die Steuerung auf rechenintensiven Algorithmen wie etwa fĂŒr die tomographische 3D Rekonstruktion der Probe basiert. Um hierzu einen effizienten Algorithmus zu implementieren, verwenden wir ein hochgradig parallelisiertes Framework. Dessen Ausgabe kann dann zur Berechnung verschiedener Bildmetriken verwendet werden, um quantitative Information ĂŒber die aufgenommenen Daten zu erhalten. Diese bilden die Grundlage zur Entscheidungsfindung in einem geschlossenen Regelkreis, in dem die Hardware fĂŒr die Datenakquise betrieben wird.
Die Genauigkeit des entwickelten Simulationsframeworks zeigen wir, indem wir virtuelle und reale Experimente vergleichen, die auf Gitterinterferometrie basieren und damit spezielle optische Elemente fĂŒr die Kontrastbildung einsetzen. AuĂerdem untersuchen wir im Detail den Einfluss der Bildgebungsbedingungen auf die Genauigkeit des implementierten Algorithmus fĂŒr gefilterte RĂŒckprojektion, und inwiefern unter dessen BerĂŒcksichtigung eine Optimierung der experimentellen Bedingungen möglich ist.
Wir demonstrieren die FĂ€higkeiten des von uns entwickelten Systems zur autonomen Datenakquise anhand eines in-situ Tomographieexperiments, bei dem es basierend auf 3D-Rekonstruktion die Framerate der Kamera optimiert und damit sicherstellt, dass die aufgezeichneten DatensĂ€tze ohne Artefakte rekonstruiert werden können. AuĂerdem nutzen wir unser System, um ein Tomographieexperiment mit hohem Probendurchsatz durchzufĂŒhren, bei dem viele Ă€hnliche biologische Proben gescannt werde: FĂŒr jede davon wird automatisch die tomographische Rotationsachse bestimmt und schlieĂlich zur Sicherstellung der QualitĂ€t schon wĂ€hrend der Messung ein komplettes 3D Volumen rekonstruiert. DarĂŒber hinaus fĂŒhren wir ein in-situ Laminographieexperiment durch, welches die Rissbildung in einer Materialprobe untersucht. Hierbei fĂŒhrt unser System die Datenakquise durch und rekonstruiert einen zentral gelegenen Querschnitt durch die Probe, um dessen korrekte Ausrichtung und die QualitĂ€t der Daten sicherzustellen.
Unsere Arbeit ermöglicht - basierend auf hochgenauen Simulationen - die Wahl der am besten geeigneten Startbedingungen eines Experiments, deren Feinabstimmung wĂ€hrend eines realen Experiments und schlieĂlich dessen automatische Steuerung basierend auf schneller Analyse der gerade aufgezeichneten Daten. Ein solches Vorgehen bei der Datenakquise ermöglicht neuartige in-vivo und in-situ Hochgeschwindigkeitsexperimente, die bedingt durch die hohen Datenraten nicht mehr von einer menschlichen Bedienperson gehandhabt werden könnten
Interactive GPU-based generation of solvent-excluded surfaces
The solvent-excluded surface (SES) is a popular molecular representation that gives the boundary of the molecular volume with respect to a specific solvent. SESs depict which areas of a molecule are accessible by a specific solvent, which is represented as a spherical probe. Despite the popularity of SESs, their generation is still a compute-intensive process, which is often performed in a preprocessing stage prior to the actual rendering (except for small models). For dynamic data or varying probe radii, however, such a preprocessing is not feasible as it prevents interactive visual analysis. Thus, we present a novel approach for the on-the-fly generation of SESs, a highly parallelizable, grid-based algorithm where the SES is rendered using ray-marching. By exploiting modern GPUs, we are able to rapidly generate SESs directly within the mapping stage of the visualization pipeline. Our algorithm can be applied to large time-varying molecules and is scalable, as it can progressively refine the SES if GPU capabilities are insufficient. In this paper, we show how our algorithm is realized and how smooth transitions are achieved during progressive refinement. We further show visual results obtained from real-world data and discuss the performance obtained, which improves upon previous techniques in both the size of the molecules that can be handled and the resulting frame rate.Peer ReviewedPostprint (author's final draft
Interactive Isocontouring of High-Order Surfaces
Scientists and engineers are making increasingly use of hp-adaptive discretization methods to compute simulations. While techniques for isocontouring the high-order data generated by these methods have started to appear, they typically do not facilitate interactive data exploration. This work presents a novel interactive approach for approximate isocontouring of high-order data. The method is based on a two-phase hybrid rendering algorithm. In the first phase, coarsely seeded particles are guided by the gradient of the field for obtaining an initial sampling of the isosurface in object space. The second phase performs ray casting in the image space neighborhood of the initial samples. Since the neighborhood is small, the initial guesses tend to be close to the isosurface, leading to accelerated root finding and thus efficient rendering. The object space phase affects the density of the coarse samples on the isosurface, which can lead to holes in the final rendering and overdraw. Thus, we also propose a heuristic, based on dynamical systems theory, that adapts the neighborhood of the seeds in order to obtain a better coverage of the surface. Results for datasets from computational fluid dynamics are shown and performance measurements for our GPU implementation are given
Simple, Rasterization-based Liquids
International audienceRasterization pipelines are ubiquitous today. They can be found in most of our personal computers as well as in smaller, hand-held devices--like smart phones--with lower-end hardware. However, simulating particle-based liquids requires sorting the particles which is cumbersome when using a rasterization pipeline. In this chapter, we describe a method to simulate liquids without having to sort the particles. Our method was specifically designed for these architectures and low shader model specifications (starting from shader model 3 for 3D liquids). Instead of sorting the particles, we splat them onto a grid (i.e. a 3D or 2D texture) and solve the inter-particle dynamics directly on the grid. Splatting is simple to perform in a rasterization pipeline, but can also be costly. Thanks to the simplified pass on the grid, we only need to splat the particles once. The grid also provides additional benefits: we can easily add artificial obstacles for the particles to interact with, we can ray cast the grid directly to render the liquid surface, and we can even gain a speed up over sort-based liquid solvers--such as the optimized solver found in the DirectX 11 SDK
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