Zooming and Panning
Zooming and panning are two types of interaction taking place in the image space of the visualization. However, they possibly interact with other parts of the information visualization pipeline, rather than just with the view transformation step.
Zooming
Zooming is the process of increasing or decreasing the scale of the visualized image. In a map, this means showing a smaller area of the map in more detail (zooming in), or showing a larger area in less detail (zooming out). In a timeline, this could mean showing a shorter time span in more detail, or a longer time span in less detail.
In most cases in information visualization, zooming is not merely a geometrical scaling operation (such as zooming in on a picture, simply enlarging the size in which pixels are shown). Rather, zooming in means that data can be displayed with more detail and less aggregated. Similarly, when zooming out, data needs to be aggregated more. Hence, zooming often involves not only the view transformation step, but also the data transformation and visual mapping steps as parts in the information visualization pipeline. This type of zooming is also called semantic zooming, as opposed to geometric zooming, which only affects the view transformation step.
Panning
Panning is the process of changing the geometrical translation of the visualized image. Panning does not affect visual mapping, but only view transformation. Examples for panning include:
- Moving a map's center around, such that an area to the east is now shown. In maps, panning is often possible by clicking, then dragging the mouse, then releasing. In this case, there is no zooming involved.
- Moving the visible area in a timeline. For example, the timeline first shows the time span from 600 CE to 800 CE. After panning, the time span shown covers the years 650 CE to 850 CE; the timeline was panned by 50 years.