Synopsis
		sfcell2 < vel.rsf > time.rsf shotfile=shots.rsf anglefile=angles.rsf vel=y order=4 lsint=n nt=nx*nz nr= a0=0. amax=360. traj= > rays.rsf

Rays and wavefronts can be displayed with sfplotrays.

Parameters
		float a0=0. First angle in degrees (if anglefile is not specified)   float amax=360. Maximum angle in degrees (if anglefile is not specified)   string anglefile= file with initial angles (auxiliary input file name)   bool lsint=n [y/n] if use least-squares interpolation   int nr= Number of angles (if anglefile is not specified)   int nt=nx*nz number of time steps   int order=4 Interpolation accuracy   string shotfile= file with shot locations (auxiliary input file name)   string traj=   bool vel=y [y/n] If y, the input is velocity; if n, slowness