Synopsis
		sfcconst < in.rsf > out.rsf source=o2 s=0. v0=1. angle=45. what=

Parameters
		float angle=45. rotation angle (counter-clock wise with respect to vertically downward)   float s=0. complex source shift   float source=o2 real source point (on surface)   float v0=1. constant velocity background   string what= what to compute (default exact solution)