Browsing by Author "Eisemann, Elmar"

Now showing 1 - 10 of 10
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    Conservative Ray Batching using Geometry Proxies
    (The Eurographics Association, 2020) Molenaar, Mathijs; Eisemann, Elmar; Wilkie, Alexander and Banterle, Francesco
    We present a method for improving batched ray traversal as was presented by Pharr et al. [PKGH97]. We propose to use conservative proxy geometry to more accurately determine whether a ray has a possibility of hitting any geometry that is stored on disk. This prevents unnecessary disk loads and thus reduces the disk bandwidth.
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    Directed Acyclic Graph Encoding for Compressed Shadow Maps
    (The Eurographics Association, 2021) Scandolo, Leonardo; Eisemann, Elmar; Binder, Nikolaus and Ritschel, Tobias
    Detailed shadows in large-scale environments are challenging. Our approach enables efficient detailed shadow computations for static environments at a low memory cost. It builds upon compressed precomputed multiresolution hierarchies but uses a directed acyclic graph to encode its tree structure. Further, depth values are compressed and stored separately and we use a bit-plane encoding for the lower tree levels entries in order to further reduce memory requirements and increase locality. We achieve between 20% to 50% improved compression rates, while retaining high performance.
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    Gradient‐Guided Local Disparity Editing
    (© 2019 The Eurographics Association and John Wiley & Sons Ltd., 2019) Scandolo, Leonardo; Bauszat, Pablo; Eisemann, Elmar; Chen, Min and Benes, Bedrich
    Stereoscopic 3D technology gives visual content creators a new dimension of design when creating images and movies. While useful for conveying emotion, laying emphasis on certain parts of the scene, or guiding the viewer's attention, editing stereo content is a challenging task. Not respecting comfort zones or adding incorrect depth cues, for example depth inversion, leads to a poor viewing experience. In this paper, we present a solution for editing stereoscopic content that allows an artist to impose disparity constraints and removes resulting depth conflicts using an optimization scheme. Using our approach, an artist only needs to focus on important high‐level indications that are automatically made consistent with the entire scene while avoiding contradictory depth cues and respecting viewer comfort.
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    MegaViews: Scalable Many‐View Rendering With Concurrent Scene‐View Hierarchy Traversal
    (© 2019 The Eurographics Association and John Wiley & Sons Ltd., 2019) Kol, Timothy R.; Bauszat, Pablo; Lee, Sungkil; Eisemann, Elmar; Chen, Min and Benes, Bedrich
    We present a scalable solution to render complex scenes from a large amount of viewpoints. While previous approaches rely either on a scene or a view hierarchy to process multiple elements together, we make full use of both, enabling sublinear performance in terms of views and scene complexity. By concurrently traversing the hierarchies, we efficiently find shared information among views to amortize rendering costs. One example application is many‐light global illumination. Our solution accelerates shadow map generation for virtual point lights, whose number can now be raised to over a million while maintaining interactive rates.
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    Model-based Visualization for Medical Education and Training
    (The Eurographics Association, 2019) Smit, Noeska; Lawonn, Kai; Kraima, Annelot; deRuiter, Marco; Bruckner, Stefan; Eisemann, Elmar; Vilanova, Anna; Bruckner, Stefan and Oeltze-Jafra, Steffen
    Anatomy, or the study of the structure of the human body, is an essential component of medical education. Certain parts of human anatomy are considered to be more complex to understand than others, due to a multitude of closely related structures. Furthermore, there are many potential variations in anatomy, e.g., different topologies of vessels, and knowledge of these variations is critical for many in medical practice. Some aspects of individual anatomy, such as the autonomic nerves, are not visible in individuals through medical imaging techniques or even during surgery, placing these nerves at risk for damage. 3D models and interactive visualization techniques can be used to improve understanding of this complex anatomy, in combination with traditional medical education paradigms. We present a framework incorporating several advanced medical visualization techniques and applications for teaching and training purposes, which is the result of an interdisciplinary project. In contrast to previous approaches which focus on general anatomy visualization or direct visualization of medical imaging data, we employ model-based techniques to represent variational anatomy, as well as anatomy not visible from imaging. Our framework covers the complete spectrum including general anatomy, anatomical variations, and anatomy in individual patients. Applications within our framework were evaluated positively with medical users, and our educational tool for general anatomy is in use in a Massive Open Online Course (MOOC) on anatomy, which had over 17000 participants worldwide in the first run.
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    A New Baseline for Feature Description on Multimodal Imaging of Paintings
    (The Eurographics Association, 2022) Toorn, Jules van der; Wiersma, Ruben; Vandivere, Abbie; Marroquim, Ricardo; Eisemann, Elmar; Ponchio, Federico; Pintus, Ruggero
    Multimodal imaging is used by conservators and scientists to study the composition of paintings. To aid the combined analysis of these digitisations, such images must first be aligned. Rather than proposing a new domain-specific descriptor, we explore and evaluate how existing feature descriptors from related fields can improve the performance of feature-based painting digitisation registration. We benchmark these descriptors on pixel-precise, manually aligned digitisations of ''Girl with a Pearl Earring'' by Johannes Vermeer (c. 1665, Mauritshuis) and of ''18th-Century Portrait of a Woman''. As a baseline we compare against the well-established classical SIFT descriptor. We consider two recent descriptors: the handcrafted multimodal MFD descriptor, and the learned unimodal SuperPoint descriptor. Experiments show that SuperPoint starkly increases description matching accuracy by 40% for modalities with little modality-specific artefacts. Further, performing craquelure segmentation and using the MFD descriptor results in significant description matching accuracy improvements for modalities with many modalityspecific artefacts.
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    Semi-Automatic Perspective Lines from Paintings
    (The Eurographics Association, 2022) Coudert-Osmont, Yoann; Eisemann, Elmar; Marroquim, Ricardo; Ponchio, Federico; Pintus, Ruggero
    Perspective cues play an important role in painting analysis as it may unveil important characteristics about the painter's techniques and creation process. Nevertheless, extracting perspective lines and their corresponding vanishing points is usually a laborious manual task. Moreover, small variations in the lines may lead to large variations in the vanishing points. In this work, we propose a semi-automatic method to extract perspective lines from paintings in order to mitigate the human variability factor and reduce the workload.
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    Spectral Processing of Tangential Vector Fields
    (© 2017 The Eurographics Association and John Wiley & Sons Ltd., 2017) Brandt, Christopher; Scandolo, Leonardo; Eisemann, Elmar; Hildebrandt, Klaus; Chen, Min and Zhang, Hao (Richard)
    We propose a framework for the spectral processing of tangential vector fields on surfaces. The basis is a Fourier‐type representation of tangential vector fields that associates frequencies with tangential vector fields. To implement the representation for piecewise constant tangential vector fields on triangle meshes, we introduce a discrete Hodge–Laplace operator that fits conceptually to the prominent discretization of the Laplace–Beltrami operator. Based on the Fourier representation, we introduce schemes for spectral analysis, filtering and compression of tangential vector fields. Moreover, we introduce a spline‐type editor for modelling of tangential vector fields with interpolation constraints for the field itself and its divergence and curl. Using the spectral representation, we propose a numerical scheme that allows for real‐time modelling of tangential vector fields.We propose a framework for the spectral processing of tangential vector fields on surfaces. The basis is a Fourier‐type representation of tangential vector fields that associates frequencies with tangential vector fields. To implement the representation for piecewise constant tangential vector fields on triangle meshes, we introduce a discrete Hodge–Laplace operator that fits conceptually to the prominent discretization of the Laplace–Beltrami operator. Based on the Fourier representation, we introduce schemes for spectral analysis, filtering and compression of tangential vector fields.
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    A Survey on Gradient-Domain Rendering
    (The Eurographics Association and John Wiley & Sons Ltd., 2019) Hua, Binh-Son; Gruson, Adrien; Petitjean, Victor; Zwicker, Matthias; Nowrouzezahrai, Derek; Eisemann, Elmar; Hachisuka, Toshiya; Giachetti, Andrea and Rushmeyer, Holly
    Monte Carlo methods for physically-based light transport simulation are broadly adopted in the feature film production, animation and visual effects industries. These methods, however, often result in noisy images and have slow convergence. As such, improving the convergence of Monte Carlo rendering remains an important open problem. Gradient-domain light transport is a recent family of techniques that can accelerate Monte Carlo rendering by up to an order of magnitude, leveraging a gradient-based estimation and a reformulation of the rendering problem as an image reconstruction. This state of the art report comprehensively frames the fundamentals of gradient-domain rendering, as well as the pragmatic details behind practical gradient-domain uniand bidirectional path tracing and photon density estimation algorithms. Moreover, we discuss the various image reconstruction schemes that are crucial to accurate and stable gradient-domain rendering. Finally, we benchmark various gradient-domain techniques against the state-of-the-art in denoising methods before discussing open problems.
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    Visual Analysis of RIS Data for Endmember Selection
    (The Eurographics Association, 2022) Popa, Andra; Gabrieli, Francesca; Kroes, Thomas; Krekeler, Anna; Alfeld, Matthias; Lelieveldt, Boudewijn; Eisemann, Elmar; Höllt, Thomas; Ponchio, Federico; Pintus, Ruggero
    Reflectance Imaging Spectroscopy (RIS) is a hyperspectral imaging technique used for investigating the molecular composition of materials. It can help identify pigments used in a painting, which are relevant information for art conservation and history. For every scanned pixel, a reflectance spectrum is obtained and domain experts look for pure representative spectra, called endmembers, which could indicate the presence of particular pigments. However, the identification of endmembers can be a lengthy process, which requires domain experts to manually select pixels and visually inspect multiple spectra in order to find accurate endmembers that belong to the historical context of an investigated painting. We propose an integrated interactive visual-analysis workflow, that combines dimensionality reduction and linked visualizations to identify and inspect endmembers. Here, we present initial results, obtained in collaboration with domain experts.