Input System

Reading Key Press and difference between GetKey, GetKeyDown and GetKeyUp

Input must must read from the Update function.

Reference for all the available Keycode enum.

1. Reading key press with Input.GetKey:

Input.GetKey will repeatedly return true while the user holds down the specified key. This can be used to repeatedly fire a weapon while holding the specified key down. Below is an example of bullet auto-fire when the Space key is held down. The player doesn’t have to press and release the key over and over again.

public GameObject bulletPrefab;
public float shootForce = 50f;

void Update()
{
    if (Input.GetKey(KeyCode.Space))
    {
        Debug.Log("Shooting a bullet while SpaceBar is held down");

        //Instantiate bullet
        GameObject bullet = Instantiate(bulletPrefab, transform.position, transform.rotation) as GameObject;

        //Get the Rigidbody from the bullet then add a force to the bullet
        bullet.GetComponent<Rigidbody>().AddForce(bullet.transform.forward * shootForce);
    }
}

2.Reading key press with Input.GetKeyDown:

Input.GetKeyDown will true only once when the specified key is pressed. This is the key difference between Input.GetKey and Input.GetKeyDown. One example use of its use is to toggle a UI or flashlight or an item on/off.

public Light flashLight;
bool enableFlashLight = false;

void Update()
{
    if (Input.GetKeyDown(KeyCode.Space))
    {
        //Toggle Light 
        enableFlashLight = !enableFlashLight;
        if (enableFlashLight)
        {
            flashLight.enabled = true;
            Debug.Log("Light Enabled!");
        }
        else
        {
            flashLight.enabled = false;
            Debug.Log("Light Disabled!");
        }
    }
}

3.Reading key press with Input.GetKeyUp:

This is the exact opposite of Input.GetKeyDown. It is used to detect when key-press is released/lifted. Just like Input.GetKeyDown, it returns true only once. For example, you can enable light when key is held down with Input.GetKeyDown then disable the light when key is released with Input.GetKeyUp.

public Light flashLight;
void Update()
{
    //Disable Light when Space Key is pressed
    if (Input.GetKeyDown(KeyCode.Space))
    {
        flashLight.enabled = true;
        Debug.Log("Light Enabled!");
    }

    //Disable Light when Space Key is released
    if (Input.GetKeyUp(KeyCode.Space))
    {
        flashLight.enabled = false;
        Debug.Log("Light Disabled!");
    }
}

Read Accelerometer Sensor (Basic)

Input.acceleration is used to read the accelerometer sensor. It returns Vector3 as a result which contains x,y and z axis values in 3D space.

void Update()
{
    Vector3 acclerometerValue = rawAccelValue();
    Debug.Log("X: " + acclerometerValue.x + "  Y: " + acclerometerValue.y + "  Z: " + acclerometerValue.z);
}

Vector3 rawAccelValue()
{
    return Input.acceleration;
}

Read Accelerometer Sensor (Advance)

Using raw values directly from the accelerometer sensor to move or rotate a GameObject can cause problems such as jerky movements or vibrations. It is recommended to smooth out the values before using them. In fact, values from the accelerometer sensor should always be smoothed out before use. This can be accomplished with a low pass filter and this is where Vector3.Lerp comes into place.

//The lower this value, the less smooth the value is and faster Accel is updated. 30 seems fine for this
const float updateSpeed = 30.0f;

float AccelerometerUpdateInterval = 1.0f / updateSpeed;
float LowPassKernelWidthInSeconds = 1.0f;
float LowPassFilterFactor = 0;
Vector3 lowPassValue = Vector3.zero;

void Start()
{
    //Filter Accelerometer
    LowPassFilterFactor = AccelerometerUpdateInterval / LowPassKernelWidthInSeconds;
    lowPassValue = Input.acceleration;
}

void Update()
{

    //Get Raw Accelerometer values (pass in false to get raw Accelerometer values)
    Vector3 rawAccelValue = filterAccelValue(false);
    Debug.Log("RAW X: " + rawAccelValue.x + "  Y: " + rawAccelValue.y + "  Z: " + rawAccelValue.z);

    //Get smoothed Accelerometer values (pass in true to get Filtered Accelerometer values)
    Vector3 filteredAccelValue = filterAccelValue(true);
    Debug.Log("FILTERED X: " + filteredAccelValue.x + "  Y: " + filteredAccelValue.y + "  Z: " + filteredAccelValue.z);
}

//Filter Accelerometer
Vector3 filterAccelValue(bool smooth)
{
    if (smooth)
        lowPassValue = Vector3.Lerp(lowPassValue, Input.acceleration, LowPassFilterFactor);
    else
        lowPassValue = Input.acceleration;

    return lowPassValue;
}

Read Accelerometer Sensor(Precision)

Read the accelerometer Sensor with precision.

This example allocates memory:

void Update()
{
    //Get Precise Accelerometer values 
    Vector3 accelValue = preciseAccelValue();
    Debug.Log("PRECISE X: " + accelValue.x + "  Y: " + accelValue.y + "  Z: " + accelValue.z);

}

Vector3 preciseAccelValue()
{
    Vector3 accelResult = Vector3.zero;
    foreach (AccelerationEvent tempAccelEvent in Input.accelerationEvents)
    {
        accelResult = accelResult + (tempAccelEvent.acceleration * tempAccelEvent.deltaTime);
    }
    return accelResult;
}

This example does not allocates memory:

void Update()
{
    //Get Precise Accelerometer values 
    Vector3 accelValue = preciseAccelValue();
    Debug.Log("PRECISE X: " + accelValue.x + "  Y: " + accelValue.y + "  Z: " + accelValue.z);

}

Vector3 preciseAccelValue()
{
    Vector3 accelResult = Vector3.zero;
    for (int i = 0; i < Input.accelerationEventCount; ++i)
    {
        AccelerationEvent tempAccelEvent = Input.GetAccelerationEvent(i);
        accelResult = accelResult + (tempAccelEvent.acceleration * tempAccelEvent.deltaTime);
    }
    return accelResult;
}

Note that this is not filtered. Please look here for how to smooth accelerometer values to remove noise.

Read Mouse Button ( Left, Middle, Right) Clicks

These functions are used to check Mouse Button Clicks.

Input.GetMouseButton(int button);
Input.GetMouseButtonDown(int button);
Input.GetMouseButtonUp(int button);

They all take the-same parameter.

0 = Left Mouse Click.
1 = Right Mouse Click.
2 = Middle Mouse Click.

GetMouseButton is used to detect when mouse button is continuously held down. It returns true while the specified mouse button is being held down.

void Update()
{
    if (Input.GetMouseButton(0))
    {
        Debug.Log("Left Mouse Button Down");
    }

    if (Input.GetMouseButton(1))
    {
        Debug.Log("Right Mouse Button Down");
    }

    if (Input.GetMouseButton(2))
    {
        Debug.Log("Middle Mouse Button Down");
    }
}

GetMouseButtonDown is used to detect when there is mouse click. It returns true if it is pressed once. It won’t return true again until the mouse button is released and pressed again.

void Update()
{
    if (Input.GetMouseButtonDown(0))
    {
        Debug.Log("Left Mouse Button Clicked");
    }

    if (Input.GetMouseButtonDown(1))
    {
        Debug.Log("Right Mouse Button Clicked");
    }

    if (Input.GetMouseButtonDown(2))
    {
        Debug.Log("Middle Mouse Button Clicked");
    }
}

GetMouseButtonUp is used to detect when the specififed mouse button is released. This is will only return true once the specified mouse button is released. To return true again, it has to be pressed and released again.

void Update()
{
    if (Input.GetMouseButtonUp(0))
    {
        Debug.Log("Left Mouse Button Released");
    }

    if (Input.GetMouseButtonUp(1))
    {
        Debug.Log("Right Mouse Button Released");
    }

    if (Input.GetMouseButtonUp(2))
    {
        Debug.Log("Middle Mouse Button Released");
    }
}