Synopsis
		sfgsrayvti < in.rsf > out.rsf vel=slow.rsf velz=slowz.rsf velx=slowx.rsf iq= niter=50 tol=0.000002*nx*nz vti_eps=0.0 vti_gamma=0.0 vti_delta=0.0 vti=

Parameters
		int iq= switch for escape variable 0=x, 1=a, 2=t, 3=z, 4=l   int niter=50 number of Gauss-Seidel iterations   float tol=0.000002*nx*nz accuracy tolerance   file vel= auxiliary input file name   file velx= auxiliary input file name   file velz= auxiliary input file name   string vti= what to compute (p=qP, v=qSV, h=SH)   float vti_delta=0.0 VTI constants Thomsen   float vti_eps=0.0   float vti_gamma=0.0