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    Explaining Neighborhood Preservation for Multidimensional Projections
    (The Eurographics Association, 2015) Martins, Rafael Messias; Minghim, Rosane; Telea, Alexandru C.; Rita Borgo and Cagatay Turkay
    Dimensionality reduction techniques are the tools of choice for exploring high-dimensional datasets by means of low-dimensional projections. However, even state-of-the-art projection methods fail, up to various degrees, in perfectly preserving the structure of the data, expressed in terms of inter-point distances and point neighborhoods. To support better interpretation of a projection, we propose several metrics for quantifying errors related to neighborhood preservation. Next, we propose a number of visualizations that allow users to explore and explain the quality of neighborhood preservation at different scales, captured by the aforementioned error metrics.We demonstrate our exploratory views on three real-world datasets and two state-of-the-art multidimensional projection techniques.
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    Tiled Projection Onto Deforming Screens
    (The Eurographics Association, 2015) Kim, Hyosun; Schinko, Christoph; Havemann, Sven; Redi, Ivan; Redi, Andrea; Fellner, Dieter W.; Rita Borgo and Cagatay Turkay
    For the next generation of visual installations it will not be sufficient to surround the visitor by stunning responsive audiovisual experiences - the next step is that space itself deforms in response to the user or user groups. Dynamic reconfigurable spaces are a new exciting possibility to influence the behaviour of groups and individuals; they may have the potential of stimulating various different social interactions and behaviours in a user-adapted fashion. However, some technical hurdles must be overcome. Projecting on larger surfaces, like a ceiling screen of 6 8 meters, is typically possible only with a tiled projection, i.e., with multiple projectors creating one large seamless image. This works well with a static ceiling; however, when the ceiling dynamically moves and deforms, the tiling becomes visible since the images no longer match. In this paper we present a method that can avoid such artifacts by dynamically adjusting the tiled projection to the deforming surface. Our method is surprisingly simple and efficient, and it does not require any image processing at runtime, nor any 3D reconstruction of the surface at any point.