Uccello studied perspective all his life in a way that was quite obsessive. Sometimes he would not come out of his house for weeks. His friend Donatello, another respected artist, begged him to do more painting and less study. Uccello became very good at mathematical calculation of the perspective of buildings, but it was not until his old age that he could fully understand how to calculate the sizes of things like people in the distance. His last painting shows a hunting party, with a great forest of trees, people and dogs, all going away into the distance, from near to far.