How did Andrea Pozzo use foreshortening and perspective in Baroque ceiling frescoes?

Andrea Pozzo was a master of the Baroque style, particularly known for his use of sotto in su—a technique involving extreme foreshortening of figures painted on ceilings to create the illusion that they are suspended in the air above the viewer.1

In his monumental work, the Allegory of the Missionary Work of the Jesuits (1691–94) on the nave vault of San Ignazio in Rome, Pozzo employed "hypertrophic illusionism" to manipulate perspective. By carefully calculating the vanishing points and the scale of his figures, he extended the architectural space of the church into the painted ceiling, blurring the boundary between the physical structure and the artistic representation. This approach built upon the theatrical traditions of the High Baroque, where artists like Pietro da Cortona and Baciccia previously used similar techniques to make figures appear to "burst out" of their frames and flood into the viewer's space.2