The Art of the Shadow: How Painters Have Gotten It Wrong for Centuries The goal is not to expose the “slipups” of the masters but to understand the human brain. Shadows do not continue from the floor up the wall on the right. Piero della Francesca, Polittico di Sant’Antonio (detail), 1460–1470. Perugia, Galleria Nazionale dell’Umbria. Image credit: © Galleria Nazionale dell’Umbria. By Roberto Ca..