import math


def blendSigmoidInc(d=0.0, u=0.0, s=1.0):
    """
        blending function increasing sigmoid
        d - Delta x = xabs - xdr
        u - Horizontal offset
        s - Tuning scale factor

        returns blend
    """
    d = float(d)
    u = float(u)
    s = float(s)

    b = 1.0/(1+math.e**(s*(u-d)))

    return b