Hi. I'm just sharing a very simple low pass filter. That's useful if you're using the raw accelerometer data which tends to have enough noise to produce quite a jittery result.
Strict
Class LowPassFilter
Field value:Float
Field alpha:Float
' dt : time interval
' rc : time constant
Method New( startValue:Float = 0, dt:Float = 0.05, rc:Float = 0.3 )
value = startValue
alpha = dt / ( rc + dt )
End
Method Update:Float( input:Float )
value = ( alpha * input ) + ( 1.0 - alpha ) * value
Return value
End
End
Depending on dt and rc values the filter may slightly delay movement, but for my purposes it works really well with the default values above.
To use it simply do something like this:
lowPassFilter = New LowPassFilter()
' and in the Update loop e.g.:
Local filteredAccelX := lowPassFilter.Update( AccelX() )
sprite.Rotation = -filteredAccelX * 90
In this case the filter smoothes out the rotation of a sprite which is controlled by the accelerometer x value. Do the same with the raw data and the sprite will look like it had a caffeine overdose.
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