Cartographic Animation in Three Dimensions: Experimenting with the Scene Graph

Cartographers have made a shift from pen and ink to digital production methods; but the digital revolution remains unfinished. Two important methods that digital production makes possible are the use of animation, and the use of three-dimensional representation. Animation, here, is considered to involve the use of motion, especially motion without continuous user input, while three-dimensional representation means the simulation of three dimensions in a two-dimensional display. The combination of these two computer graphics techniques has the potential for increasing the power of both; the two approaches are complimentary. A three-dimensional scene can be made to carry a higher density of information by using animation to vary the light source or perspective, for example, by highlighting components of a three-dimensional scene that are of particular interest. Elements unique to animation, such as rate of change and order of appearance, can be combined with elements unique to threedimensional display, like fog, lighting, and texture. However, although these elements can be combined, current cartographic theory and tools do not make it easy to do so. An addition to cartographic theory that will aid in the creation of novel combinations of three-dimensional scenes with animation is described. This addition is a categorization of possible visual variables generated by three-dimensional scenes, and ways these variables can be integrated with animation in a geovisualization context. A technical solution for combining three-dimensional display and animation, presented here, is the use of software components that can be linked together in a visual programming environment. The software used, GeoVISTA Studio, enables data sources, data transformations, data analysis, and data display, to be linked together along with user controls for these components. GeoVISTA Studio eases the creation of experimental three-dimensional animated maps.