Now showing items 1-17 of 17

    • A faster algorithm to compute the visibility map of a 1.5D terrain 

      Löffler, Maarten; Saumell, Maria; Silveira, Rodrigo Ignacio (2014)
      Conference report
      Open Access
      Given a 1.5D terrain, i.e., an x -monotone polygonal line in R 2 with n vertices, and 1 m n viewpoints placed on some of the terrain vertices, we study the problem of computing the parts of the terrain that are visible ...
    • Adjacency-preserving spatial treemaps 

      Buchin, Kevin; Eppstein, David; Löffler, Maarten; Nöllenburg, Martin; Silveira, Rodrigo Ignacio (2016)
      Article
      Open Access
      Rectangular layouts, subdivisions of an outer rectangle into smaller rectangles, have many applications in visualizing spatial information, for instance in rectangular cartograms in which the rectangles represent geographic ...
    • Colored spanning graphs for set visualization 

      Hurtado Díaz, Fernando Alfredo; Korman, Matias; Van Kreveld, Matias; Löffler, Maarten; Sacristán Adinolfi, Vera; Shioura, Akiyoshi; Silveira, Rodrigo Ignacio; Speckmann, Bettina; Tokuyama, Takeshi (2018-03)
      Article
      Open Access
      We study an algorithmic problem that is motivated by ink minimization for sparse set visualizations. Our input is a set of points in the plane which are either blue, red, or purple. Blue points belong exclusively to the ...
    • Colored spanning graphs for set visualization 

      Hurtado Díaz, Fernando Alfredo; Korman Cozzetti, Matías; Van Kreveld, Matias; Löffler, Maarten; Sacristán Adinolfi, Vera; Silveira, Rodrigo Ignacio; Speckmann, Bettina (Springer, 2013)
      Conference report
      Open Access
      We study an algorithmic problem that is motivated by ink minimization for sparse set visualizations. Our input is a set of points in the plane which are either blue, red, or purple. Blue points belong exclusively to the ...
    • Computing correlation between piecewise-linear functions 

      Agarwal, Pankaj; Aronov, Boris; Van Kreveld, Matias; Löffler, Maarten; Silveira, Rodrigo Ignacio (2013)
      Article
      Restricted access - publisher's policy
      We study the problem of computing correlation between two piecewise-linear bivariate functions defined over a common domain, where the surfaces they define in three dimensions---polyhedral terrains---can be transformed ...
    • Computing similarity between piecewise-linear functions 

      Agarwal, Pankaj; Aronov, Boris; Kreveld, Marc van; Löffler, Maarten; Silveira, Rodrigo Ignacio (ACM Press. Association for Computing Machinery, 2010)
      Conference report
      Open Access
      We study the problem of computing the similarity between two piecewise-linear bivariate functions de ned over a common domain, where the surfaces they de ne in 3D|polyhedral terrains|can be transformed vertically by a ...
    • Flow computations on imprecise terrains 

      Driemel, Anne; Haverkort, Herman; Löffler, Maarten; Silveira, Rodrigo Ignacio (2013)
      Article
      Open Access
      We study water flow computation on imprecise terrains. We consider two approaches to modeling flow on a terrain: one where water flows across the surface of a polyhedral terrain in the direction of steepest descent, and ...
    • Flow computations on imprecise terrains 

      Driemel, Anne; Haverkort, Herman; Löffler, Maarten; Silveira, Rodrigo Ignacio (Springer Verlag, 2011)
      Conference report
      Restricted access - confidentiality agreement
      We study water flow computation on imprecise terrains. We consider two approaches to modeling flow on a terrain: one where water flows across the surface of a polyhedral terrain in the direction of steepest descent, and ...
    • Geomasking through perturbation, or counting points in circles 

      Löffler, Maarten; Luo, Jun; Silveira, Rodrigo Ignacio (2017)
      Conference report
      Restricted access - publisher's policy
      Motivated by a technique in privacy protection, in which n points are randomly perturbed by at most a distance r, we study the following problem: Given n points and m circles in the plane, what is the maximum r such that ...
    • Median trajectories 

      Buchin, Kevin; Buchin, Maike; Kreveld, Marc van; Löffler, Maarten; Silveira, Rodrigo Ignacio; Wenk, Carola; Wiratma, Lionov (2012-05)
      Article
      Open Access
      We investigate the concept of a median among a set of trajectories. We establish criteria that a “median trajectory” should meet, and present two different methods to construct a median for a set of input trajectories. The ...
    • On the complexity of barrier resilience for fat regions and bounded ply 

      Korman, Matias; Löffler, Maarten; Silveira, Rodrigo Ignacio; Strash, Darren (2018-06)
      Article
      Open Access
      In the barrier resilience problem (introduced by Kumar et al., Wireless Networks 2007), we are given a collection of regions of the plane, acting as obstacles, and we would like to remove the minimum number of regions so ...
    • Processing aggregated data : the location of clusters in health data 

      Buchin, Kevin; Buchin, Maike; Kreveld, Marc van; Löffler, Maarten; Luo, Jun; Silveira, Rodrigo Ignacio (2012-07)
      Article
      Restricted access - publisher's policy
      Spatially aggregated data is frequently used in geographical applications. Often spatial data analysis on aggregated data is performed in the same way as on exact data, which ignores the fact that we do not know the actual ...
    • Region-based approximation algorithms for visibility between imprecise locations 

      Buchin, Kevin; Kostitsyna, Irina; Löffler, Maarten; Silveira, Rodrigo Ignacio (2015)
      Conference report
      Restricted access - publisher's policy
      In this paper we present new geometric algorithms for approximating the visibility between two imprecise locations amidst a set of obstacles, where the imprecise locations are modeled by continuous probability distributions. ...
    • Region-based approximation of probability distributions (for visibility between imprecise points among obstacles) 

      Buchin, Kevin; Kostitsyna, Irina; Löffler, Maarten; Silveira, Rodrigo Ignacio (2014)
      Conference report
      Open Access
      Let p and q be two imprecise points, given as prob- ability density functions on R 2 , and let R be a set of n line segments in R 2 . We study the problem of approximating the probability that p and q can see each other; ...
    • Region-based approximation of probability distributions (for visibility between imprecise points among obstacles) 

      Buchin, Kevin; Kostitsyna, Irina; Löffler, Maarten; Silveira, Rodrigo Ignacio (2019-07)
      Article
      Open Access
      Let p and q be two imprecise points, given as probability density functions on R2 , and let O be a set of disjoint polygonal obstacles in R2 . We study the problem of approximating the probability that p and q can see each ...
    • Removing local extrema from imprecise terrains 

      Gray, Chris; Kammer, Frank; Löffler, Maarten; Silveira, Rodrigo Ignacio (2012-08)
      Article
      Open Access
      In this paper we consider imprecise terrains, that is, triangulated terrains with a vertical error interval in the vertices. In particular, we study the problem of removing as many local extrema (minima and maxima) as ...
    • Terrain visibility with multiple viewpoints 

      Hurtado Díaz, Fernando Alfredo; Löffler, Maarten; Matos, Inés P.; Sacristán Adinolfi, Vera; Saumell, Maria; Silveira, Rodrigo Ignacio; Staals, Frank (Springer, 2013)
      Conference report
      Open Access
      We study the problem of visibility in polyhedral terrains in the presence of multiple viewpoints. We consider three fundamental visibility structures: the visibility map, the colored visibility map, and the Voronoi visibility ...