Refers to a perspective system derived from linear perspective, but employing curved lines to account for the optical illusion that wide or tall forms at right angles to the viewer's line of sight undergo perspectival diminution towards their extreme edges. In this system, a wide wall parallel to the picture plane would appear to taper at the left and right. The system was discussed by Leonardo da Vinci in the Renaissance, but was not often used until the 19th and 20th centuries.
