Part of the problem, of course, is that one views "Girls" or "The Sessions" in the dark — or, at least, in the kind of isolation that the theater does not easily afford. On film, your eye sees the action only from angles carefully selected. The sex in "Girls" has the laudable aura of frank spontaneity, but it's an illusion. One sees not the strings. Onstage, especially in the small venues common in Chicago, your inevitably broader view of the action is frequently framed by other audience members. At "Teddy Ferrara" last week, I watched the sex scenes with a squirming high-school-age girl in one part of my field of vision, and a tough-to-read senior gentleman in another. One cannot help but watch them watch what you're watching. "What are they thinking?" you think, which pulls you out of the scene.