3D wave interference

This surface represents the interference of 2 waves in 3D. It is generated by the function [math] f(x,y) = \frac{sin(10 (sqrt((x + 1)² + (y + 1)²) + a))}{ sqrt((x + 1)² + (y + 1)²)} + \frac{sin(10 (sqrt((x - 1)² + (y - 1)²) + a))}{ sqrt((x - 1)² + (y - 1)²)}[/math]