Synopsis
		sfvofz > out.rsf n1= n= n2= n= g=1. v0=0.5 s=0.5 d1=0.5/(n1-1) d2=1./(n2-1) o1=0. o2=0. intime=n

Parameters
		float d1=0.5/(n1-1) vertical sampling   float d2=1./(n2-1) horizontal sampling   float g=1. velocity gradient   bool intime=n [y/n] if in vertical time coordinates   int n= number of samples   int n1= vertical samples   int n2= horizontal samples   float o1=0. vertical origin   float o2=0. horizontal origin   float s=0.5 shot location at the surface   float v0=0.5 initial velocity