sfcell2 (2.1-git)
Second-order cell ray tracing with locally parabolic rays.

        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.

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