Definition: <m>f®= 1 - 22*r^2/{9*d^2} + 17*r^4/{9*d^4} - 4*r^6/{9*d^6}</m>
r - distance to the given point

Call: hfSoft(x,x0,y0,z0,d,T);

Parameters:

x - point coordinates

x0,y0,z0 - arrays of blob centers

d - array of d - radii of influence

T - threshold value

Test file: soft.hf