Visitors to the Yale University Art Gallery can now observe how American painter Edward Hopper transformed a charcoal sketch depicting a wall, a door and a floor into a sunlit interior conveying eerie isolation. Earlier this summer, the gallery acquired two preparatory drawings for Hopper’s famous paintings “Rooms by the Sea” and “Western Motel,” which are both in the gallery’s American art collection. The drawings reveal the creative process of the artist and show how he pared down many details from his initial composition to achieve an effect of stark simplicity in the final product. Gallery Director Jock Reynolds said the drawings are invaluable for studying the works of Hopper, particularly since X-rays of his completed paintings depict few alterations. “These wonderful working drawings … provide important documentary information about the paintings to which they are related,” Reynolds said. “For the gallery, where studio art and art history students are a constant presence, such works provide a terrific teaching resource.”