Greenfield’s raw material, materialism, is candy-colored and stimulating. It is also almost uniformly depressing. In “Generation Wealth,” she shows us the self-starved bodies of the affluent young, among their parents’ magma-flow of possessions. We see their marmoreal homes, their beauty regimes, and their fathers’ younger, heliotropic second wives. The overall affect of the exhibition’s packed two floors and the accompanying book, a dense gold brick with some 650 images, is nihilism. At times, it even feels gleefully so.