Dynamic Path Exploration on Mobile Devices

1 OCCLUSION FUNCTION To evaluate o(Li(xc,yc)), we leverage the vector data we downloaded from the OSM database and render all containing roads into a grayscale image buffer B whose extent is chosen according to the map area of the cell domain and whose resolution is chosen to resemble the resolution of the output device. Since roads are encoded in the OSM as simple polylines, for simplicity reasons we choose a constant line thickness for all roads that corresponds to a road width of 8 meters. We use two different gray values: Road segments which correspond to the path p(t) are drawn in pure white (1.0). For all other roads we choose a darker color to indicate their smaller importance (usually 0.25). Areas which do not belong to roads remain black (0.0). In order to compute o(Li(xc,yc)) for a detail lens Li that is placed at a cell c inside the domain, we evaluate the corresponding pixel extent of the detail lens in the grayscale image buffer B and denote the pixel coordinates in B defining this extent as xmin xc,i ,x max xc,i ,y min yc,i and y max yc,i . Finally, we define o(Li(xc,yc)) as