colored : boolean
textured : boolean
Fig. 3 OutputRendering representation
( ObjectAttached ) where the objects are those described in CityGML (OGC 12-019
2012 ). In this last case a spatial relation can be specified (above, below, etc.). The
OutputRendering class is represented in Fig. 3 .
Figure 5 shows the description of air quality visualization as colored spheres
positioned on a surface (1 m above terrain level) while Fig. 4 shows an illustration
of the described technique.
3.4 Usage Representation
Evaluating a 3D visualization technique for specific tasks and contexts refers to
the usability of the technique. Few authors have performed such evaluations. One
can quote Vaaraniemi et al. ( 2013 ) who have performed both qualitative and quan-
titative user evaluations. The aim was the comparison of techniques developed for
enhancing the visibility of textual labels in 3D navigation maps as those labels
can become occluded. Since many techniques are widely used without any formal
evaluation it is better to talk of usage instead of usability, this usage to be defined
according to a task and a context.