Variable screening

In one embodiment, a variable screen includes a generally flat sheet having a front surface, a back surface, and a plurality of elongated slits that extend through the sheet from the front surface to the back surface, wherein the sheet includes a shape memory material that enables the slits to open into openings through which light and fluid can pass when a tensile force is applied to the sheet in a direction generally perpendicular to the slits and further enables the slits and openings to automatically when the tensile force is removed