Techniques for forming a mask fabrication layout for a physical integrated circuit design layout include correcting the fabrication layout for proximity effects using a proximity effects model. A proximity effects model is executed to produce an initial output. The initial output is based on a first position for a segment in a fabrication layout. The first position is displaced from a corresponding original edge in the original fabrication layout by a distance equal to an initial bias. The model is also executed to produce a second output based on a second position for the segment. The second position is displaced from the corresponding original edge by a distance equal to a second bias. An optimal bias for the segment is determined based on the initial output and the second output. The segment is displaced in the fabrication layout from the corresponding edge based on the optimal bias.