A method of constructing a channel mask for an autostereoscopic display, the display including an electronically controlled screen covered by a parallax filter device that includes a refractive medium and is configured to obscure certain areas on the screen for a left eye of a viewer and to obscure certain other areas on the screen for a right eye of the viewer, the channel mask being a two-dimensional geometric object that permits to assign to each point on the screen one of a number of viewing positions of an eye of the viewer, the method including the step of constructing the channel mask by tracing light rays that propagate from selected points on the screen and are refracted at the parallax filter device.