Browsing by Author "Zeidan, Mahmoud"

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    Moment-Based Opacity Optimization
    (The Eurographics Association, 2020) Zeidan, Mahmoud; Rapp, Tobias; Peters, Christoph; Dachsbacher, Carsten; Frey, Steffen and Huang, Jian and Sadlo, Filip
    Geometric structures such as points, lines, and surfaces play a vital role in scientific visualization. However, these visualizations frequently suffer from visual clutter that hinders the inspection of important features behind dense but less important features. In the past few years, geometric cluttering and occlusion avoidance has been addressed in scientific visualization with various approaches such as opacity optimization techniques. In this paper, we present a novel approach for opacity optimization based on recent state-of-the-art moment-based techniques for signal reconstruction. In contrast to truncated Fourier series, momentbased reconstructions of feature importance and optical depth along view rays are highly accurate for sparse regions but also plausible for densely covered regions. At the same time, moment-based methods do not suffer from ringing artifacts. Moreover, this representation enables fast evaluation and compact storage, which is crucial for per-pixel optimization especially for large geometric structures. We also present a fast screen space filtering approach for optimized opacities that works directly on moment buffers. This filtering approach is suitable for real-time visualization applications, while providing comparable quality to object space smoothing. Its implementation is independent of the type of geometry such that it is general and easy to integrate. We compare our technique to recent state of the art techniques for opacity optimization and apply it to real and synthetic data sets in various applications.
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    Versatile Geometric Flow Visualization by Controllable Shape and Volumetric Appearance
    (The Eurographics Association, 2022) Zeidan, Mahmoud; Peters, Christoph; Rapp, Tobias; Dachsbacher, Carsten; Cabiddu, Daniela; Schneider, Teseo; Allegra, Dario; Catalano, Chiara Eva; Cherchi, Gianmarco; Scateni, Riccardo
    We present a novel visualization technique for geometry-based visualization of vector fields. Our approach generalizes and combines several existing approaches in a flexible framework using a scalable GPU-accelerated implementation. We map characteristic lines to a variety of glyphs. The user can define multiple cross-sectional shapes that will be used for extrusion. Our system interpolates between these shapes as requested, either based on attributes of the vector field and the characteristic lines or using global user-controlled parameters. Thus, a single characteristic line can use different cross-sectional shapes in different parts to aid the visualization of different phenomena. Transitions can be smooth or discrete and we support highlighting of silhouettes. Additionally, we track and visualize the rotation in the vector field and offer full control of the color mapping, the opacity and the radii along the characteristic lines. Texture-based approaches such as 3D line integral convolution (3D LIC) offer another avenue to vector field visualization. In 3D, they typically rely on sparsely placed seed points. We emulate their appearance with our geometry-based approach through an approximation of the volume integral within our glyphs. Combined with fast order-independent transparency, our GPU implementation achieves fast rendering, even at high resolutions, while keeping the memory footprint moderate.