The axis of the driver transform that is compared against the falloff regions. Typically the axis that is pointing at the child; usually X by convention. Default is X-axis (1,0,0).
The size of the falloff region (yellow) that defines the start of the output range. A value of 1 wraps the entire sphere with falloff. Range is 0-1. Default is 0.2.
The normalized output parameter; ranges from 0 (when outside yellow region) to 1 (in the green region) and smoothly blends from 0-1 in the yellow region.