Visual simulation of the external environment has become an essential part of devices used in flight and air combat training. In the case of a highly maneuverable aircraft, such as a fighter, the pilot's visual field-of-view is extremely large. As a result, many of the modern air combat simulators use the inner surface of a spherical dome as the display screen for the projection of surrounding imagery, such as other aircraft and ground features. When the reflected scene appears brighter than that from a Lambertian surface, the screen is said to exhibit gain. The increase in brightness results from redirecting the incident light along a preferred path. As the apparent gain increases in the preferred direction, less light is reflected in other directions, resulting in a sharp drop in apparent brightness. When the reflecting surface is curved, as is the inner surface of a spherical dome, the preferred direction of reflection is continually changing. Placement of the projectors and the location of the observer, together with a high surface gain, comprise the complex projection system development.