Filter utilities: a deadband expander

FilterUtilities.cs

public static partial class FilterUtilities
{
	// @kurtdekker
	//
	// Part of Jetpack Kurt Space Flight available for iOS/Android
	//
	// Evalutes a normalized analog input signal (such as an analog
	// axis) and filters it:
	//
	// If signal is below the deadband in absolute magnitude:
	//	- set signal to zero
	//	- return false, no input present in signal
	//
	// If signal is at or above the deadband in absolute magnitude:
	//	- re-zero-scale the signal from 0 to 1 (preserving sign!)
	//	- return true, yes we have input
	//
	// The purpose is to allow deadbands without a discontinuity
	// (eg, no sudden snap from 0.0 to deadband minimum)
	//
	// Expected signal input domain is [-1 .. +1]. You are responsible for this.
	// Expected deadband input is zero or positive, but always less than +1
	//
	public static bool DeadbandAndExpand( ref float axis, float deadband)
	{
		bool haveInput = false;

		if (axis < 0)
		{
			if (axis > -deadband)
			{
				axis = 0;
			}
			else
			{
				haveInput = true;
				axis = (axis + deadband) / ( 1.0f - deadband);
			}
		}
		else
		{
			if (axis < deadband)
			{
				axis = 0;
			}
			else
			{
				haveInput = true;
				axis = (axis - deadband) / ( 1.0f - deadband);
			}
		}

		return haveInput;
	}
}