This operator computes a number between zero and one. The return code is 0 if the amount passed in is less than or equal to the first value, 1 if the amount is greater than or equal to the second value. If the amount is within range, a smooth (easin/easeout) interpolation is computed.
If a rolloff is specified, the inflection point of the blend will be shifted. If the rolloff is greater than 1, the shift will be to the right. If the rolloff is less than 1 (and greater than 0), the shift will be to the left.