6 Understanding the Illusion of Perspective together along the horizon line at a point called the vanishing point. 5 Sets of parallel lines that do not correspond to a horizontal ground plane, like the front and back angled edges of a slanted roof, have an oblique vanishing point. Perspective is the technique of depicting dimensional objects on a flat surface. In other words, it's the illusion of depth where none actually exists. Cameras perform this illusion as they capture the three-dimensional images of beings, places and things and display them