Synopsis
		sfimpl3 < in.rsf > out.rsf rect1= rect2= rect3= tau=0.1 pclip=50. up=n verb=n nsnap=1 dist= snap=

Parameters
		string dist= inverse distance file (input)   int nsnap=1 number of snapshots   float pclip=50. percentage clip for the gradient   float rect1=   float rect2=   float rect3= smoothing radius   string snap= snapshot file (output)   float tau=0.1 smoothing time   bool up=n [y/n] smoothing style   bool verb=n [y/n] verbosity flag