Dipl.-Inf. Marco Ament

VISUS - Visualization Research Center
Universität Stuttgart
Allmandring 19
D-70569 Stuttgart, Germany

Room: 01.033, OG Ost
Email: marco.ament [at] vis.uni-stuttgart.de
Phone: +49 (0)711 / 685-88634
www: http://www.vis.uni-stuttgart.de/~amentmo/

Research:

Projects:

Photo-realistic and Interactive Visualization of Astronomical Objects for Digital Planetariums
(DFG, "Astrographik")

Abstract: This DFG-funded project aims to model astrophysical objects physically consistent for lifelike and fast 3D visualization. Therefore, methods and algorithms are developed to reconstruct the spatial structure of various objects from astronomical observations and physical constraints to visualize them interactively with modern, high-resolution planetarium displays. Cosmological effects are visualized based on scientific facts in an accessible manner for the public.

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Book Chapter: GPU-Accelerated Visualization M. Ament, S. Frey, C. Müller, S. Grottel, T. Ertl, and D. Weiskopf Editors: E. W. Bethel, H. Childs, and C. Hansen. High Performance Visualization: Enabling Extreme-Scale Scientific Insight. Chapman and Hall/CRC, ISBN-13: 978-1439875728, pages 223-260, 2012. Purchase book No details available Download BibTeX

Abstract: The visualization of large data is a computationally demanding task. The increase in performance and the flexible programmability have made graphics processing units (GPUs) an attractive platform to address large data visualization. The parallel architecture of GPUs and the low costs, coupled with high availability, have paved the way for this significant field of research. In this chapter, we review the fundamental principles of modern graphics hardware briefly before we summarize the latest research in GPU-based visualization techniques for stand-alone and cluster-based systems.

Spectral Analysis of Higher-Order and BFECC Texture Advection R. Netzel, M. Ament, M. Burch, and D. Weiskopf Proceedings of the Workshop on Vision, Modeling, and Visualization (VMV), pages 87-94, 2012. Download PDF Details Download BibTeX

Abstract: We present a spectral analysis of higher-order texture advection in combination with Back and Forth Error Compensation and Correction (BFECC). Semi-Lagrangian techniques exhibit high numerical diffusion, which acts as a low-pass filter and tends to smooth out high frequencies. In the spatial domain, numerical diffusion leads to a loss of details and causes a blurred image. To reduce this effect, higher-order interpolation methods or BFECC can be employed separately. In this paper, we present a combination of both approaches and we analyze the quality of different compositions of higher-order interpolation schemes with and without BFECC. We employ radial power spectrum diagrams for different advection times and input textures to evaluate the conservation of the spectrum up to fifth-order polynomials. Our evaluation shows that the results of texture advection are improved by using higher-order interpolation.

Visualization of Astronomical Nebulae via Distributed Multi-GPU Compressed Sensing Tomography S. Wenger, M. Ament, S. Guthe, D. Lorenz, A. Tillmann, D. Weiskopf, and M. Magnor IEEE Transactions on Visualization and Computer Graphics, 18(12): 2188-2197, 2012. (Proceedings of IEEE Visualization 2012) Download PDF Movie Download BibTeX

Abstract: The 3D visualization of astronomical nebulae is a challenging problem since only a single 2D projection is observable from our fixed vantage point on Earth. We attempt to generate plausible and realistic looking volumetric visualizations via a tomographic approach that exploits the spherical or axial symmetry prevalent in some relevant types of nebulae. Different types of symmetry can be implemented by using different randomized distributions of virtual cameras. Our approach is based on an iterative compressed sensing reconstruction algorithm that we extend with support for position-dependent volumetric regularization and linear equality constraints. We present a distributed multi-GPU implementation that is capable of reconstructing high-resolution datasets from arbitrary projections. Its robustness and scalability are demonstrated for astronomical imagery from the Hubble Space Telescope. The resulting volumetric data is visualized using direct volume rendering. Compared to previous approaches, our method preserves a much higher amount of detail and visual variety in the 3D visualization, especially for objects with only approximate symmetry.

Interactive Visualization and Simulation of Astronomical Nebulae S. Wenger, M. Ament, W. Steffen, N. Koning, D. Weiskopf, and M. Magnor IEEE Computing in Science and Engineering, 14(3): 78-87, 2012. http://dx.doi.org/10.1109/MCSE.2012.52 Download PDF Details coming soon... Download BibTeX

Abstract: Interactive visualization and simulation of astrophysical phenomena enable digital planetariums and television documentaries to take their spectators on a journey into deep space and explore the astronomical wonders of our universe in 3D.

GPU-Based Four-Dimensional General-Relativistic Ray Tracing D. Kuchelmeister, T. Müller, M. Ament, G. Wunner, and D. Weiskopf Computer Physics Communications, 183(10): 2282–2290, 2012. http://dx.doi.org/10.1016/j.cpc.2012.04.030 Download PDF Details coming soon... Download BibTeX

Abstract: This paper presents a new general-relativistic ray tracer that enables image synthesis on an interactive basis by exploiting the performance of graphics processing units (GPUs). The application is capable of visualizing the distortion of the stellar background as well as trajectories of moving astronomical objects orbiting a compact mass. Its source code includes metric definitions for the Schwarzschild and Kerr spacetimes that can be easily extended to other metric definitions, relying on its object-oriented design. The basic functionality features a scene description interface based on the scripting language Lua, real-time image output, and the ability to edit almost every parameter at runtime. The ray tracing code itself is implemented for parallel execution on the GPU using NVidia’s Compute Unified Device Architecture (CUDA), which leads to performance improvement of an order of magnitude compared to a single CPU and makes the application competitive with small CPU cluster architectures.

GPU-Based Two-Dimensional Flow Simulation Steering using Coherent Structures M. Ament, S. Frey, F. Sadlo, T. Ertl, and D. Weiskopf Proceedings of the 2nd International Conference on Parallel, Distributed, Grid and Cloud Computing for Engineering, paper 18, 2011. http://dx.doi.org/10.4203/ccp.95.18 Download PDF Interactive Demo Download BibTeX

Abstract: We present an exemplary steering system that performs 2D flow simulation and visualization on graphics processing units (GPUs). The topology of a vector field provides the overall structure and therefore lends itself for steering purposes. We build on the concept of Lagrangian coherent structures present as ridges in the finite-time Lyapunov exponent (FTLE). This allows to perform steering with respect to the true time-dependent dynamics in a given time scope. Based on the insights from the FTLE visualization, our CUDA-based implementation allows effective interactive manipulation of boundary conditions such as solid obstacles or velocity profiles.

Sort First Parallel Volume Rendering B. Moloney, M. Ament, D. Weiskopf, and T. Möller IEEE Transactions on Visualization and Computer Graphics, 17(8): 1164-1177, 2011. http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.116 Download PDF Details coming soon... Download BibTeX

Abstract: Sort first distributions have been studied and used far less than sort last distributions for parallel volume rendering, especially when the data is too large to be replicated fully. We demonstrate that sort first distributions are not only a viable method of performing data scalable parallel volume rendering, but more importantly they allow for a range of rendering algorithms and techniques that are not efficient with sort last distributions. Several of these algorithms are discussed and two of them are implemented in a parallel environment: a new improved variant of early ray termination to speed up rendering when volumetric occlusion occurs and a volumetric shadowing technique that produces more realistic and informative images based on half angle slicing. Improved methods of distributing the computation of the load balancing and loading portions of a subdivided data set are also presented. Our detailed test results for a typical GPU cluster with distributed memory show that our sort first rendering algorithm outperforms sort last rendering in many scenarios.

Direct Interval Volume Visualization M. Ament, D. Weiskopf, and H. Carr IEEE Transactions on Visualization and Computer Graphics, 16(6): 1505-1514, 2010. (Proceedings of IEEE Visualization 2010) http://doi.ieeecomputersociety.org/10.1109/TVCG.2010.145 Download PDF Movie Download BibTeX

Abstract: We extend direct volume rendering with a unified model for generalized isosurfaces, also called interval volumes, allowing a wider spectrum of visual classification. We generalize the concept of scale-invariant opacity—typical for isosurface rendering—to semi-transparent interval volumes. Scale-invariant rendering is independent of physical space dimensions and therefore directly facilitates the analysis of data characteristics. Our model represents sharp isosurfaces as limits of interval volumes and combines them with features of direct volume rendering. Our objective is accurate rendering, guaranteeing that all isosurfaces and interval volumes are visualized in a crack-free way with correct spatial ordering. We achieve simultaneous direct and interval volume rendering by extending preintegration and explicit peak finding with data-driven splitting of ray integration and hybrid computation in physical and data domains. Our algorithm is suitable for efficient parallel processing for interactive applications as demonstrated by our CUDA implementation.

A Parallel Preconditioned Conjugate Gradient Solver for the Poisson Problem on a Multi-GPU Platform M. Ament, G. Knittel, D. Weiskopf, and W. Straßer Proceedings of the 18th Euromicro Conference on Parallel, Distributed and Network-based Computing (PDP), pages 583-592, 2010. http://doi.ieeecomputersociety.org/10.1109/PDP.2010.51 Download PDF Download BibTeX

Abstract: We present a parallel conjugate gradient solver for the Poisson problem optimized for multi-GPU platforms. Our approach includes a novel heuristic Poisson preconditioner which is well-suited for massively-parallel SIMD processing. Furthermore, we address the problem of limited transfer rates over typical data channels such as the PCI-express bus relative to the bandwidth requirements of powerful GPUs. Specifically, naïve communication schemes can severely reduce the achievable speedup in such communication-intense algorithms. For this reason, we employ overlapping memory transfers to establish a high level of concurrency and to improve scalability. We have implemented our model on a high-performance workstation with multiple hardware accelerators. We will discuss the mathematical principles, give implementation details, and present the performance and the scalability of the system.

Dynamic Grid Refinement for Fluid Simulations on Parallel Graphics Architectures M. Ament and W. Straßer Proceedings of the Eurographics Symposium on Parallel Graphics and Visualization (EGPGV), pages 9-15, 2009. http://dx.doi.org/10.2312/EGPGV/EGPGV09/009-015 Download PDF Details (images + movies) Download BibTeX

Cover of EGPGV Proceedings 2009

Abstract: We present a physically-based fluid simulation with dynamic grid refinement on parallel SIMD graphics hardware. The irregular and dynamic structure of an adaptive grid requires sophisticated memory access patterns as well as a decomposition of the problem for parallel processing and the distribution of tasks to multiple threads. In this paper, we focus on the representation and management of the dynamic grid on the graphics device for an efficient parallelization of the advection step and the iterative solving of the Poisson equation. In order to achieve high performance, we utilize the hardware’s capabilities like fast cache access and trilinear filtering. Furthermore, expensive data transfer between host and device is minimized to avoid a major bottleneck. We report results on the inherent overhead of the dynamic grid compared to an equivalent Cartesian grid. In addition, a visual simulation of smoke is presented with radiosity-based illumination and volume ray casting at interactive frame rates.

Hardware Accelerated Fluid Dynamics with Adaptive Grid Refinement M. Ament WSI/GRIS, University of Tübingen, Diploma Thesis, 2008. Download PDF

Abstract: In this thesis, a physically-based fluid simulation with dynamic grid refinement parallel SIMD graphics hardware is presented. The irregular and dynamic structure of an adaptive grid requires sophisticated memory access patterns as well as a decomposition of the problem for parallel processing and the distribution of tasks to multiple threads. The focus of this thesis lies on the representation and management of the dynamic grid on the graphics device for an efficient parallelization of the advection step and the iterative solving of the Poisson equation. In order to achieve high performance, the hardware's capabilities like fast cache access and trilinear filtering are utilized. Furthermore, expensive data transfer between host and device is minimized to avoid a major bottleneck. Results on the inherent overhead of the dynamic grid compared to an equivalent Cartesian grid are reported. In addition, a visual simulation of smoke is presented with radiosity-based illumination and volume ray casting at interactive frame rates.