1. A method for generating a three-dimensional (3D) model of a grading transition, comprising: receiving grading transition data specifying a footprint, an initial grading distance, and an ending grading distance; determining a grading distance transition rate using the initial grading distance and the ending grading distance; generating a daylight line by sweeping a circle along the footprint, wherein the radius of the circle increases according to the grading distance transition rate, and wherein the circle is centered on the footprint; and assigning elevation values to stations along the daylight line.