Better Perception of 3D-Spatial Relations by Viewport Variations

Computer-graphics and especially virtual 3D worlds evolve to important tools for digital cartography, where the main aim of efficient spatial communication rules processes of conception, design and dissemination. This paper investigates the enhancement of visual spatial relations in virtual 3D worlds, which's limitation on standard displays is a main drawback of digital cartography. The main limitations of digital cartography concern the extension of viewing plane and its resolution, which have impact on information depth of the map content, transmitting an overview, thus the highlighting of spatial relations and additional request for cognitive load. These drawbacks are not only limited to 2D maps, but are also existing in virtual 3D environments, where additional geometric characteristics, like perspective distortions, multiple scales or overriding, may influence a correct extraction of spatial-related content. On the other hand these specific geometric disadvantages should be formulated as benefit of 3D, especially when infinite numbers of scale can be combined in a "natural way" or spatial content becomes extracted by naive interaction. One main limitation of digital presentations generally persists: the limitation of the presentation area on standard displays, which leads to a very restricted overview and fewer visible relations of spatial content. View-port variations that modify perspective and/or orthographic projections are one possibility to enhance rendering methods in a way that the main disadvantages of regular perspective views become decreased and the perceptibility for an overview and spatial relations expanded. These variations cover progressive and degressive central-perspectives as well as progressive and degressive "parallel-perspectives", which provide very specific characteristics in use with spatial information transmission. This contribution focuses on enhancing virtual spatial relations in 3D environments by using view-port variations, that modify perspective and orthographic views in a progressive and degressive way. Provided that standard displays deliver significant limitations for effective and expressive geo-communication with virtual 3D environments, offers by 3D cartography are discussed. An exemplary comparison of actual 3D city models allows to identify "dead values" and gives one clue for the requested modification. The description and exemplary visualization of view-port varia-tions lead to their theoretical communication aspects, which will guide pragmatic (user) studies in future.