Dynamic Label Placement in Practice

We consider the problem of labeling dynamic (3D) maps: we develop real-time algorithms that attach non-overlapping annotations to objects on maps which the user can pan, zoom, and rotate continuously. Existing algorithms either label static maps or only a small number of the objects. We consider the problem to label streets and to label points. We label streets either internally or externally. For internal labels, we compute potential label positions for each street, compare them, and decide for one. For external street labels, we apply a force-directed approach; labels behave like electrons. The first algorithm for labeling points allows labels to slide along their reference points; it makes use of visibilities between labels. The other approach precomputes for each point an interval of zoom levels at which the label can be placed; labelings are queried at run time.