Synopsis
		sfdrays < vel.rsf > gbeam.rsf shotfile=shots.rsf anglefile=angles.rsf rays=rays.rsf dmat=dmat.rsf proj=proj.rsf mask=mask.rsf vel=y order=4 nt= dt= verb=y shift=0.5 zshot=0. yshot=o[1]+0.5*(n[1]-1)*d[1] nr= a0=0. amax=360.

Angle is 90 deg along y-axis and 180 deg along z-axis, clockwise.

Parameters
		float a0=0. minimum angle (if no anglefile)   float amax=360. maximum angle (if no anglefile)   string anglefile= file with initial angles [nr,nshot] (auxiliary input file name)   string dmat= auxiliary output file name   float dt= Sampling in time   string mask= auxiliary output file name   int nr= number of angles (if no anglefile)   int nt= Number of time steps   int order=4 Interpolation order   string proj= auxiliary output file name   string rays= auxiliary output file name   float shift=0.5 Complex source shift   string shotfile= file with shot locations [zshot,yshot,nshot] (auxiliary input file name)   bool vel=y [y/n] If y, input is velocity; if n, slowness   bool verb=y [y/n] Verbosity flag   float yshot=o[1]+0.5*(n[1]-1)*d[1]   float zshot=0.