Sfumato is the 'smoky' quality which blurs contours so that figures emerge from a dark background by means of gradual tonal modulations without any harsh outlines. Leonardo da Vinci advised painting 'without lines' in his uncompleted treatise on painting, and this atmospheric quality can be seen in his own works. It was also introduced in Venice by Giorgione, whose paintings show such subtle transitions of tone that the figures almost fuse with their surroundings.