@misc{LimbergerGroplerBuschmannetal.2018,
  author    = {Limberger, Daniel and Gropler, Anne and Buschmann, Stefan and D{\"o}llner, J{\"u}rgen Roland Friedrich and Wasty, Benjamin},
  title     = {OpenLL},
  series = {22nd International Conference Information Visualisation (IV)},
  journal   = {22nd International Conference Information Visualisation (IV)},
  publisher = {IEEE},
  address   = {New York},
  isbn      = {978-1-5386-7202-0},
  doi       = {10.1109/iV.2018.00039},
  pages     = {175 -- 181},
  year      = {2018},
  abstract  = {Today's rendering APIs lack robust functionality and capabilities for dynamic, real-time text rendering and labeling, which represent key requirements for 3D application design in many fields. As a consequence, most rendering systems are barely or not at all equipped with respective capabilities. This paper drafts the unified text rendering and labeling API OpenLL intended to complement common rendering APIs, frameworks, and transmission formats. For it, various uses of static and dynamic placement of labels are showcased and a text interaction technique is presented. Furthermore, API design constraints with respect to state-of-the-art text rendering techniques are discussed. This contribution is intended to initiate a community-driven specification of a free and open label library.},
  language  = {en}
}
@article{VollmerTrappSchumannetal.2018,
  author    = {Vollmer, Jan Ole and Trapp, Matthias and Schumann, Heidrun and D{\"o}llner, J{\"u}rgen Roland Friedrich},
  title     = {Hierarchical spatial aggregation for level-of-detail visualization of 3D thematic data},
  series = {ACM transactions on spatial algorithms and systems},
  volume    = {4},
  journal   = {ACM transactions on spatial algorithms and systems},
  number    = {3},
  publisher = {Association for Computing Machinery},
  address   = {New York},
  issn      = {2374-0353},
  doi       = {10.1145/3234506},
  pages     = {23},
  year      = {2018},
  abstract  = {Thematic maps are a common tool to visualize semantic data with a spatial reference. Combining thematic data with a geometric representation of their natural reference frame aids the viewer's ability in gaining an overview, as well as perceiving patterns with respect to location; however, as the amount of data for visualization continues to increase, problems such as information overload and visual clutter impede perception, requiring data aggregation and level-of-detail visualization techniques. While existing aggregation techniques for thematic data operate in a 2D reference frame (i.e., map), we present two aggregation techniques for 3D spatial and spatiotemporal data mapped onto virtual city models that hierarchically aggregate thematic data in real time during rendering to support on-the-fly and on-demand level-of-detail generation. An object-based technique performs aggregation based on scene-specific objects and their hierarchy to facilitate per-object analysis, while the scene-based technique aggregates data solely based on spatial locations, thus supporting visual analysis of data with arbitrary reference geometry. Both techniques can apply different aggregation functions (mean, minimum, and maximum) for ordinal, interval, and ratio-scaled data and can be easily extended with additional functions. Our implementation utilizes the programmable graphics pipeline and requires suitably encoded data, i.e., textures or vertex attributes. We demonstrate the application of both techniques using real-world datasets, including solar potential analyses and the propagation of pressure waves in a virtual city model.},
  language  = {en}
}
@article{SemmoHildebrandtTrappetal.2012,
  author    = {Semmo, Amir and Hildebrandt, Dieter and Trapp, Matthias and D{\"o}llner, J{\"u}rgen Roland Friedrich},
  title     = {Concepts for cartography-oriented visualization of virtual 3D city models},
  series = {Photogrammetrie, Fernerkundung, Geoinformation},
  journal   = {Photogrammetrie, Fernerkundung, Geoinformation},
  number    = {4},
  publisher = {Schweizerbart},
  address   = {Stuttgart},
  issn      = {1432-8364},
  doi       = {10.1127/1432-8364/2012/0131},
  pages     = {455 -- 465},
  year      = {2012},
  abstract  = {Virtual 3D city models serve as an effective medium with manifold applications in geoinformation systems and services. To date, most 3D city models are visualized using photorealistic graphics. But an effective communication of geoinformation significantly depends on how important information is designed and cognitively processed in the given application context. One possibility to visually emphasize important information is based on non-photorealistic rendering, which comprehends artistic depiction styles and is characterized by its expressiveness and communication aspects. However, a direct application of non-photorealistic rendering techniques primarily results in monotonic visualization that lacks cartographic design aspects. In this work, we present concepts for cartography-oriented visualization of virtual 3D city models. These are based on coupling non-photorealistic rendering techniques and semantics-based information for a user, context, and media-dependent representation of thematic information. This work highlights challenges for cartography-oriented visualization of 3D geovirtual environments, presents stylization techniques and discusses their applications and ideas for a standardized visualization. In particular, the presented concepts enable a real-time and dynamic visualization of thematic geoinformation.},
  language  = {en}
}
@article{SemmoTrappJobstetal.2015,
  author    = {Semmo, Amir and Trapp, Matthias and Jobst, Markus and D{\"o}llner, J{\"u}rgen Roland Friedrich},
  title     = {Cartography-Oriented Design of 3D Geospatial Information Visualization - Overview and Techniques},
  series = {The cartographic journal},
  volume    = {52},
  journal   = {The cartographic journal},
  number    = {2},
  publisher = {Routledge, Taylor \& Francis Group},
  address   = {Leeds},
  issn      = {0008-7041},
  doi       = {10.1080/00087041.2015.1119462},
  pages     = {95 -- 106},
  year      = {2015},
  abstract  = {In economy, society and personal life map-based interactive geospatial visualization becomes a natural element of a growing number of applications and systems. The visualization of 3D geospatial information, however, raises the question how to represent the information in an effective way. Considerable research has been done in technology-driven directions in the fields of cartography and computer graphics (e.g., design principles, visualization techniques). Here, non-photorealistic rendering (NPR) represents a promising visualization category - situated between both fields - that offers a large number of degrees for the cartography-oriented visual design of complex 2D and 3D geospatial information for a given application context. Still today, however, specifications and techniques for mapping cartographic design principles to the state-of-the-art rendering pipeline of 3D computer graphics remain to be explored. This paper revisits cartographic design principles for 3D geospatial visualization and introduces an extended 3D semiotic model that complies with the general, interactive visualization pipeline. Based on this model, we propose NPR techniques to interactively synthesize cartographic renditions of basic feature types, such as terrain, water, and buildings. In particular, it includes a novel iconification concept to seamlessly interpolate between photorealistic and cartographic representations of 3D landmarks. Our work concludes with a discussion of open challenges in this field of research, including topics, such as user interaction and evaluation.},
  language  = {en}
}