Sometimes also referred to as aerial perspective, atmospheric perspective is a technique first utilized in fresco painting during the Roman era that allows for the three-dimensional representation of outdoor scenes. The technique entails blurring objects, figures, and other elements within the landscape that are in the distance, as they would look if the eye were to perceive them in a real outdoor setting. Its effectiveness also depends on the softening of colors used for the rendering of those distant elements. The technique was reintroduced in the 15th century by Masaccio, who first used it in his frescoes in the Brancacci Chapel, Florence (c. 1425).
Historical dictionary of Renaissance art. Lilian H. Zirpolo. 2008.