Heinrich Wolfflin, the art historian, observed that late Renaissance paintings offered their terrific sense of illusion because of a concept he called “closed vs. open form”. One edge of a subject would have a hard defining edge and, the other side would dissolve into space. He explained this quality as the difference between linear description and painterly description which better evoked the sensation of space and volume. Linear description circumscribes each object or figure with a hard edge ( see the Pintoricchio fresco detail above). Figures look as though they are cut out and glued onto the image. Leonardo da Vinci would later invent a system he called s’fumato, or smoky edged, which blends the edges of the subject into its surrounding space. Our sense of stereoptic vision works like that. We see with fuzzy edges. I present two examples of “open and closed form ” here. The “Evening Landscape” is an oil painting. I dissolved some of the edges of the clouds and hardened others. The combination provides a feeling of unified volume. In the other forest and water piece which is a watercolor sketch, notice that edges of the rocks appear and dissolve as do tree trunks and even territories of foliage.