A light fixture example includes a housing, a light source in the housing and a diffuser. The diffuser is supported by the housing at a distance from the source so as to receive light from the source and diffuse the light for illumination. The diffuser has a three-dimensional compound curvature and a perimeter with at least two edges connected at vertices. Each such edge is a two-dimensional plane curve. The at least two edges are not coplanar with each other. In some examples, a back panel of the housing may have a similar three-dimensional compound curvature and perimeter.