Synopsis
		sfirays < in.rsf > out.rsf t0=ot0.rsf x0=ox0.rsf f0=of0.rsf velocity=y order=1 thres=10.

Parameters
		string f0= auxiliary output file name   int order=1 fastmarching accuracy order   string t0= auxiliary output file name   float thres=10. thresholding for caustics   bool velocity=y [y/n] y, inputs are velocity / n, slowness-squared   string x0= output upwind neighbor (auxiliary output file name)

Used In
		TCCS          time2depth2/synth