Real-Time Rendering of Eclipses without Incorporation of Atmospheric Effects

In this paper, we present a novel approach for real-time rendering of soft eclipse shadows cast by spherical, atmosphereless bodies. While this problem may seem simple at first, it is complicated by several factors. First, the extreme scale differences and huge mutual distances of the involved celestial bodies cause rendering artifacts in practice. Second, the surface of the Sun does not emit light evenly in all directions (an effect which is known as limb darkening). This makes it impossible to model the Sun as a uniform spherical light source. Finally, our intended applications include real-time rendering of solar eclipses in virtual reality, which require very high frame rates. As a solution to these problems, we precompute the amount of shadowing into an eclipse shadow map, which is parametrized so that it is independent of the position and size of the occluder. Hence, a single shadow map can be used for all spherical occluders in the Solar System. We assess the errors introduced by various simplifications and compare multiple approaches in terms of performance and precision. Last but not least, we compare our approaches to the state-of-the-art and to reference images. The implementation has been published under the MIT license

Comparison of Depth Buffer Techniques for Large and Detailed 3D Scenes

Large scale 3D scenes in applications like space simulations are often subject to depth buffer related issues and visual artefacts like Z-fighting and spatial jittering. These issues are primarily a result of indistinguishable depth buffer values. To mitigate these issues, many techniques have been developed over time to better distribute depth values over the clipping range. These techniques range from simple adjustments of the projection matrix to complex solutions like multistage rendering with layered depth buffers. This work presents, compares and evaluates commonly used approaches found in iterature and real world applications. An experiment is set up to compare the presented depth buffer techniques using the metric of minimum triangle separation (MTS). The gathered results are presented and evaluated, to give a good overview on which techniques are well suited for the use in applications with large scale 3D scenes

Minimal renormalization without epsilon-expansion: Amplitude functions in three dimensions below T_c

Massive field theory at fixed dimension d<4 is combined with the minimal subtraction scheme to calculate the amplitude functions of thermodynamic quantities for the O(n) symmetric phi^4 model below T_c in two-loop order. Goldstone singularities arising at an intermediate stage in the calculation of O(n) symmetric quantities are shown to cancel among themselves leaving a finite result in the limit of zero external field. From the free energy we calculate the amplitude functions in zero field for the order parameter, specific heat and helicity modulus (superfluid density) in three dimensions. We also calculate the q^2 part of the inverse of the wavenumber-dependent transverse susceptibility chi_T(q) which provides an independent check of our result for the helicity modulus. The two-loop contributions to the superfluid density and specific heat below T_c turn out to be comparable in magnitude to the one-loop contributions, indicating the necessity of higher-order calculations and Pade-Borel type resummations.Comment: 41 pages, LaTeX, 8 PostScript figures, submitted to NPB [FS

Scaling and Synchronization in Deterministic and Stochastic Nonlinear Dynamical Systems

Subject of this work is the investigation of universal scaling laws which are observed in coupled chaotic systems. Progress is made by replacing the chaotic fluctuations in the perturbation dynamics by stochastic processes. First, a continuous-time stochastic model for weakly coupled chaotic systems is introduced to study the scaling of the Lyapunov exponents with the coupling strength (coupling sensitivity of chaos). By means of the the Fokker-Planck equation scaling relations are derived, which are confirmed by results of numerical simulations. Next, the new effect of avoided crossing of Lyapunov exponents of weakly coupled disordered chaotic systems is described, which is qualitatively similar to the energy level repulsion in quantum systems. Using the scaling relations obtained for the coupling sensitivity of chaos, an asymptotic expression for the distribution function of small spacings between Lyapunov exponents is derived and compared with results of numerical simulations. Finally, the synchronization transition in strongly coupled spatially extended chaotic systems is shown to resemble a continuous phase transition, with the coupling strength and the synchronization error as control and order parameter, respectively. Using results of numerical simulations and theoretical considerations in terms of a multiplicative noise partial differential equation, the universality classes of the observed two types of transition are determined (Kardar-Parisi-Zhang equation with saturating term, directed percolation).Gegenstand dieser Arbeit ist die Untersuchung universeller Skalengesetze, die in gekoppelten chaotischen Systemen beobachtet werden. Ergebnisse werden erzielt durch das Ersetzen der chaotischen Fluktuationen in der Störungsdynamik durch stochastische Prozesse. Zunächst wird ein zeitkontinuierliches stochastisches Modell für schwach gekoppelte chaotische Systeme eingeführt, um die Skalierung der Lyapunov-Exponenten mit der Kopplungsstärke (coupling sensitivity of chaos) zu untersuchen. Mit Hilfe der Fokker-Planck-Gleichung werden Skalengesetze hergeleitet, die von Ergebnissen numerischer Simulationen bestätigt werden. Anschließend wird der neuartige Effekt der vermiedenen Kreuzung von Lyapunov-Exponenten schwach gekoppelter ungeordneter chaotischer Systeme beschrieben, der qualitativ der Abstoßung zwischen Energieniveaus in Quantensystemen ähnelt. Unter Benutzung der für die coupling sensitivity of chaos gewonnenen Skalengesetze wird ein asymptotischer Ausdruck für die Verteilungsfunktion kleiner Abstände zwischen Lyapunov-Exponenten hergeleitet und mit Ergebnissen numerischer Simulationen verglichen. Schließlich wird gezeigt, dass der Synchronisationsübergang in stark gekoppelten räumlich ausgedehnten chaotischen Systemen einem kontinuierlichen Phasenübergang entspricht, mit der Kopplungsstärke und dem Synchronisationsfehler als Kontroll- beziehungsweise Ordnungsparameter. Unter Benutzung von Ergebnissen numerischer Simulationen sowie theoretischen Überlegungen anhand einer partiellen Differentialgleichung mit multiplikativem Rauschen werden die Universalitätsklassen der zwei beobachteten Übergangsarten bestimmt (Kardar-Parisi-Zhang-Gleichung mit Sättigungsterm, gerichtete Perkolation)

Usability Testing of Visual Policy Evaluation for Network Security Event Detection

The network security framework VisITMeta allows the visual evaluation and management of security event detection policies. By means of a "what-if" simulation the sensitivity of policies to specific events can be tested and adjusted. This paper presents the results of a user study for testing the usability of the approach by measuring the correct completion of given tasks as well as the user satisfaction by means of the system usability scale

Hyperchaotic Dynamics and Synchronization of External-Cavity Semiconductor Lasers

Two unidirectionally coupled external cavity semiconductor lasers showing chaotic intensity fluctuations are studied by numerically solving the LangKobayashi model equations [IEEE J. Quantum Electron. QE-16, 347 (1980)]. The systems are shown to synchronize when operating in the regime of lowfrequency fluctuations which is characterized by a very high-dimensional (d ? 150) attractor. The influence of parameter differences between the two lasers on the synchronization quality is investigated. PACS number(s): 05.45.+b, 42.55.Px, 42.65.Sf Typeset using REVT E X I. INTRODUCTION Synchronization phenomena are of fundamental importance for many physical, biological, and technical systems. Since the pioneering work by Fujisaka and Yamada [1], Pikovsky [2], and Afraimovich, Verichev and Rabinovich [3] it is known that even chaotic systems may synchronize. This aspect of nonlinear dynamics became an issue of great interest when Pecora and Carroll demonstrated synchronization of uni-directiona..

Applying Microservice Principles to Simulation Tools

The usage of microservices promises a lot of benefits concerning scalability and maintainability, rewriting large monoliths is however not always possible. Especially in scientific projects, pure microservice architectures are therefore not feasible in every project. We propose the utilization of microservice principles for the construction of microsimulations for urban transport. We present a prototypical architecture for the connection of MATSim and AnyLogic, two widely used simulation tools in the context of urban transport simulation. The proposed system combines the two tools into a singular tool supporting civil engineers in decision making on innovative urban transport concepts