How can I detect a shake motion on a mobile device using Unity3D? C#

Question

I would have assumed unity has some event trigger for this but I can't find one in the Unity3d documentation. Would I need to work with changes in the accelerometer?

Thank you all.

Answer 1

Excellent discussion regarding detecting "shaking" can be found in this thread on the Unity forums.

From Brady's post:

From what I can tell in some of the Apple iPhone sample apps, you basically just set a vector magnitude threshold, set a high-pass filter on the accelerometer values, then if the magnitude of that acceleration vector is ever longer than your set threshold, it's considered a "shake".

jmpp's suggested code (modified for readability and to be closer to valid C#):

float accelerometerUpdateInterval = 1.0f / 60.0f;
// The greater the value of LowPassKernelWidthInSeconds, the slower the
// filtered value will converge towards current input sample (and vice versa).
float lowPassKernelWidthInSeconds = 1.0f;
// This next parameter is initialized to 2.0 per Apple's recommendation,
// or at least according to Brady! ;)
float shakeDetectionThreshold = 2.0f;

float lowPassFilterFactor;
Vector3 lowPassValue;

void Start()
{
    lowPassFilterFactor = accelerometerUpdateInterval / lowPassKernelWidthInSeconds;
    shakeDetectionThreshold *= shakeDetectionThreshold;
    lowPassValue = Input.acceleration;
}

void Update()
{
    Vector3 acceleration = Input.acceleration;
    lowPassValue = Vector3.Lerp(lowPassValue, acceleration, lowPassFilterFactor);
    Vector3 deltaAcceleration = acceleration - lowPassValue;

    if (deltaAcceleration.sqrMagnitude >= shakeDetectionThreshold)
    {
        // Perform your "shaking actions" here. If necessary, add suitable
        // guards in the if check above to avoid redundant handling during
        // the same shake (e.g. a minimum refractory period).
        Debug.Log("Shake event detected at time "+Time.time);
    }
}

Note: I recommend you read the whole thread for the full context.