Synopsis
		sfcell3 < vel.rsf > time.rsf shotfile=shots.rsf anglefile=angles.rsf vel=y order=4 nt=nx*nz na= nb= a0=0. amax=360. b0=0. bmax=180. traj= > rays.rsf

Rays and wavefronts can be displayed with sfplotrays.

Parameters
		float a0=0. First azimuth angle in degrees (if anglefile is not specified)   float amax=360. Maximum azimuth angle in degrees (if anglefile is not specified)   string anglefile= file with initial angles (auxiliary input file name)   float b0=0. First inclination angle in degrees (if anglefile is not specified)   float bmax=180. Maximum inclination angle in degrees (if anglefile is not specified)   int na= Number of azimuths (if anglefile is not specified)   int nb= Number of inclinations (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