When stereoscopic images are rendered on a single physical device, a technique called field-sequential imaging is typically used. In order to achieve this effect. the rendering system must be given information about the physical dimensions of the display (e.g., 19" diagonal monitor). Without this information, it is not possible to correctly offset the left and right eye images to appropriately match the separate between the observer's left and right eyes. Instead of providing the linear dimension of the display, Vizard requires that you specify the displays field-of-view (see viz.fov) and the viewing distance (this command).