Fill a Distance Attenuation array
recommend that the distance attenuation Point2f array is defined to
be allocated to be 10 for DOUBLE_DISTANCE_HALF_GAIN - since 1/(2^10)
exceeds 1/1000 scale that is agreed to be affective zero gain
First method assumes that:
type is half gain for every double of distance
inner radius is 0.0 but region between 0th and 1st elements is constant
since gains for these two elements are the same
min gain approches zero.
Returns the representation of the specified floating-point
value according to the IEEE 754 floating-point "single format"
bit layout, after first mapping -0.0 to 0.0.