J. Seward Johnson Jr. can make a bronze sculpture so lifelike and convincing that you’ll want to talk to it. But his latest assignment is far more daunting than any park-bench mannequin. Johnson is recreating the works of the great Impressionist painters, in bronze, in real-life scale, and in three dimensions. “Visitors [to Johnson’s exhibit in Washington] will be able to walk into Vincent van Gogh’s ‘The Bedroom’ in Arles, France. They will be invited to touch the objects, to the expected horror of conservative museum folks. They will even be able to lie down on the bed, though they won’t be able to get under the covers.”