Optical body with fresnel-rendering of complex topographical surface

An optical film or other optical body has a structured surface comprising Fresnel prisms. The Fresnel prisms define a complex topography. For example, a first and second Fresnel prism may have elongated first and second plan view shapes that form a "wye" (Y-shaped) feature. Alternatively or in addition, the Fresnel prisms may be arranged such that slopes of the Fresnel prisms define one or more saddle points. Furthermore, one or more of the Fresnel prisms may have prism shapes in plan view that include undulating portions, and the Fresnel prisms may be arranged in a slope sequence that defines one or more inflection points. The Fresnel prisms may be refractive or reflective, and they may provide the structured surface with a 3-dimensional appearance.