Browsing by Author "Preiner, Reinhold"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Augmenting Node-Link Diagrams with Topographic Attribute Maps
    (The Eurographics Association and John Wiley & Sons Ltd., 2020) Preiner, Reinhold; Schmidt, Johanna; Krösl, Katharina; Schreck, Tobias; Mistelbauer, Gabriel; Viola, Ivan and Gleicher, Michael and Landesberger von Antburg, Tatiana
    We propose a novel visualization technique for graphs that are attributed with scalar data. In many scenarios, these attributes (e.g., birth date in a family network) provide ambient context information for the graph structure, whose consideration is important for different visual graph analysis tasks. Graph attributes are usually conveyed using different visual representations (e.g., color, size, shape) or by reordering the graph structure according to the attribute domain (e.g., timelines). While visual encodings allow graphs to be arranged in a readable layout, assessing contextual information such as the relative similarities of attributes across the graph is often cumbersome. In contrast, attribute-based graph reordering serves the comparison task of attributes, but typically strongly impairs the readability of the structural information given by the graph's topology. In this work, we augment force-directed node-link diagrams with a continuous ambient representation of the attribute context. This way, we provide a consistent overview of the graph's topological structure as well as its attributes, supporting a wide range of graph-related analysis tasks. We resort to an intuitive height field metaphor, illustrated by a topographic map rendering using contour lines and suitable color maps. Contour lines visually connect nodes of similar attribute values, and depict their relative arrangement within the global context. Moreover, our contextual representation supports visualizing attribute value ranges associated with graph nodes (e.g., lifespans in a family network) as trajectories routed through this height field. We discuss how user interaction with both the structural and the contextual information fosters exploratory graph analysis tasks. The effectiveness and versatility of our technique is confirmed in a user study and case studies from various application domains.
  • Thumbnail Image
    Item
    Elastic Flattening of Painted Pottery Surfaces
    (The Eurographics Association, 2018) Preiner, Reinhold; Karl, Stephan; Bayer, Paul; Schreck, Tobias; Sablatnig, Robert and Wimmer, Michael
    Generating flat images from paintings on curved surfaces is an important task in Archaeological analysis of ancient pottery. It allows comparing styles and painting techniques, e.g, for style and workshop attribution, and serves as basis for domain publications which typically use 2d images. To obtain such flat images from scanned textured 3d models of the pottery objects, current practice is to perform so-called rollouts using approximating shape primitives like cones or spheres, onto which the mesh surfaces are projected. While this process provides in intuitive deformation metaphor for the users, it naturally introduces unwanted distortions in the mapping of the surface, especially for vessels with high-curvature profiles. In this work, we perform an elastic flattening of these projected meshes, where stretch energy is minimized by simulating a physical relaxation process on a damped elastic spring model. We propose an intuitive contraction-directed physical setup which allows for an efficient relaxation while ensuring a controlled convergence. Our work has shown to produce images of significantly improved suitability for domain experts' tasks like interpretation, documentation and attribution of ancient pottery.
  • Thumbnail Image
    Item
    Real-Time Gaussian-Product Subdivision on the GPU
    (The Eurographics Association, 2021) Komar, Alexander; Preiner, Reinhold; Andres, Bjoern and Campen, Marcel and Sedlmair, Michael
    We propose a real-time technique for rendering Gaussian-Product subdivision surfaces. This is achieved by our real-time subdivision pipeline, able to accept the base of Gaussian-Product subdivision, that is, a covariance mesh, which extends regular base meshes by storing additional 3x3 covariance matrices per vertex. Our technique evaluates the non-linear limit subdivision surface by computing B-spline patches embedded in a 9-dimensional dual space, where the subdivision scheme becomes linear. We construct and evaluate these B-spline patches using real-time tessellation capabilities of current GPUs. We analyzed the performance of our technique on all supported subdivision levels, and provide an analysis of its visual quality and geometric accuracy.
  • No Thumbnail Available
    Item
    Towards Crowd-Sourced Collaborative Fragment Matching
    (The Eurographics Association, 2023) Houska, Peter; Kloiber, Simon; Masur, Alessandra; Lengauer, Stefan; Karl, Stephan; Preiner, Reinhold; Bucciero, Alberto; Fanini, Bruno; Graf, Holger; Pescarin, Sofia; Rizvic, Selma
    Many artifacts of our archaeological heritage are preserved only in fragments. The reassembly of these parts to their original form is therefore an essential task for archaeologists. Our project aims at incorporating the intellect of many participants from the broad public in the solution of this complex task. To this end, we develop a web-based 3D environment, in which users can interactively and collaboratively reassemble virtual fragments of real-world artifacts, supported by computer-aided methods. Our primary research focus lies on identifying how to best design and setup such a system in order to maximize the collaboration efficiency. By participating in this open reassembly process, users can gain valuable insight into the archaeological task, thus raising awareness for our common cultural heritage in a multitude of people.