% smoothstep(t) returns:
%     0   if t < 0
%     1   if t > 1
%    p(t) if 0 < t < 1, where p(t) is polynomial that smoothly goes from 0 to 1
%
function y = smoothstep(t)
    s = min((t>0).*t,1);
    y = (126+(-420+(540+(-315+70*s).*s).*s).*s).*s.^5;