On the Design of Perspective Displays

FUNCTIONS OF INFORMATION DISPLAYS ometric appearance of a real environment by visually presenting static and dynamic features as if the viewer were to be actually looking at them. A viewer looking at such an image can thus interpret the image as if it represented a virtual space on the far side of the picture plane. Vehicle instrument panels, road signs, warning placards and maps are all examples of information displays. In general they may be designed to support either impressionistic, investigative, or communicative purposes. If the geometric viewpoint used to project the perspective image is updated so as to reflect the motion of the viewer, the virtual space that the viewer sees will come to take on some of the interactive appearance of a virtual environment (Brooks, 1988, Ellis, 1991). But this updating requires high fidelity tracking of the viewer's position and is not always implemented for practical or economic reasons. The present essay will be accordingly limited to nonviewer-tracked, perspective displays. An impressionistic display could be a picture intended by its artist to convey a general ambiance without unambiguous representation of the location of picture elements. An investigative display could be a data plot from a loosely controlled "experiment of nature" in which investigators were not able to manipulate experimental variables. In such a plot they would be examining data to direct subsequent possible analyses. A communicative display, in contrast, would be a plot or picture generated to specifically transmit a definite message such as the statistical significance of a particular measurement. Only this last type of display will considered below.