1. A method comprising: calculating a transmission cross coefficient (TCC(n)) in a spatial domain for a simulation of a mask pattern to provide a first result; calculating a transmission cross coefficient TCC(x 1 , y 1 , x 2 , y 2 ) in the spatial domain utilizing the first result to provide a second result; calculating intensity at x and y coordinates of a wafer (I(x, y)) in a spatial domain utilizing the second result to provide a third result, wherein calculating at least one of (TCC(n)), TCC(x 1 , y 1 , x 2 , y 2 ), and I(x, y) is performed by a processor; and reporting a result of an evaluation of the third result, wherein TCC(x 1 , y 1 , x 2 , y 2 ) is calculated with an equation TCC ⁡ ( x 1 , y 1 , x 2 , y 2 ) = ∑ n = 0 N cut ⁢ ( - ⅈπ ) n n ! ⁢ TCC ⁡ ( n ) ⁢ z n .