1. A computer-implemented method for determining a set of surface profiles, comprising: receiving a surface profile of a surface in a multilayer stack; calculating a second surface profile of a second surface in the multilayer stack based on a generalized Eikonal equation, a geometry of the multilayer stack and the surface profile, wherein the second surface is associated with a different layer in the multilayer stack than the surface, and wherein the second surface is adjacent to the surface in the multilayer stack; and repeating, one or more times, the calculation operation for additional surfaces in the multilayer stack based on a generalized Eikonal equation, a geometry of the multilayer stack, the surface profile, and surface profiles determined in preceding instances of the calculation operation, thereby determining the set of surface profiles, wherein a given additional surface is associated with a different layer in the multilayer stack than the surface profile and the surface profiles determined in preceding instances of the calculation operation, and wherein the given additional surface is adjacent to another surface in the multilayer stack that is associated with another layer in an immediately preceding instance of the calculation operation.