HP Reverb G2 Controllers in Unity
HP Motion controllers are a brand new type of Windows Mixed Reality controllers: all the same tracking technology with a slightly different set of available inputs:
- Touchpad has been replaced by two buttons: A and B for the right controller, and X and Y for the left controller.
- Grasp is now a trigger that publishes a stream of values between 0.0 and 1.0 instead of a button with Pressed and Not Pressed states.
Since the new inputs aren't accessible through existing Windows and Unity APIs, you need the dedicated Microsoft.MixedReality.Input UPM Package.
Important
Classes in this package do not replace existing Windows and Unity APIs but complement them. Features commonly available to both classic Windows Mixed Reality controllers and HP Motion Controllers are accessible through the same code path using existing APIs. Only the new inputs require the use of the additional Microsoft.MixedReality.Input package.
HP Motion Controller overview
Microsoft.MixedReality.Input.MotionController represents a motion controller. Each MotionController instance has an XR.WSA.Input.InteractionSource peer, which can be correlated using handedness, vendor ID, product ID, and version.
You can grab MotionController instances by creating a MotionControllerWatcher and subscribing to its events, similar to using InteractionManager events to discover new InteractionSource instances. The MotionController’s methods and properties describe the inputs supported by the controller, including its buttons, triggers, 2D axis, and thumbstick. The MotionController class also exposes methods for accessing input states through the MotionControllerReading class. The MotionControllerReading class represents a snapshot of the controller’s state at a given time.
Installing Microsoft.MixedReality.Input with the Mixed Reality Feature Tool
Install the Microsoft.MixedReality.Input plugin with the new Mixed Reality Feature Tool application. Follow the installation and usage instructions and select the Mixed Reality Input package in the Mixed Reality Toolkit category:
Using Microsoft.MixedReality.Input
Input values
A MotionController can expose two kinds of inputs:
- Buttons and trigger states are expressed by a unique float value between 0.0 and 1.0 that indicates how much they're pressed.
- A button can only return 0.0 (when not pressed) or 1.0 (when pressed) while a trigger can return continuous values between 0.0 (fully released) to 1.0 (fully pressed).
- Thumbstick state is expressed by a Vector2 whose X and Y components are between -1.0 and 1.0.
You can use MotionController.GetPressableInputs() to return a list of inputs returning a pressed value (buttons and triggers) or the MotionController.GetXYInputs() method to return a list of inputs returning a 2-axis value.
A MotionControllerReading instance represents the state of the controller at a given time:
- GetPressedValue() retrieves the state of a button or a trigger.
- GetXYValue() retrieves the state of a thumbstick.
Creating a cache to maintain a collection of MotionController instances and their states
Start by instantiating a MotionControllerWatcher and registering handlers for its MotionControllerAdded and MotionControllerRemoved events to keep a cache of available MotionController instances. This cache should be a MonoBehavior attached to a GameObject as demonstrated in the following code:
public class MotionControllerStateCache : MonoBehaviour
{
/// <summary>
/// Internal helper class which associates a Motion Controller
/// and its known state
/// </summary>
private class MotionControllerState
{
/// <summary>
/// Construction
/// </summary>
/// <param name="mc">motion controller</param>`
public MotionControllerState(MotionController mc)
{
this.MotionController = mc;
}
/// <summary>
/// Motion Controller that the state represents
/// </summary>
public MotionController MotionController { get; private set; }
…
}
private MotionControllerWatcher _watcher;
private Dictionary<Handedness, MotionControllerState>
_controllers = new Dictionary<Handedness, MotionControllerState>();
/// <summary>
/// Starts monitoring controller's connections and disconnections
/// </summary>
public void Start()
{
_watcher = new MotionControllerWatcher();
_watcher.MotionControllerAdded += _watcher_MotionControllerAdded;
_watcher.MotionControllerRemoved += _watcher_MotionControllerRemoved;
var nowait = _watcher.StartAsync();
}
/// <summary>
/// Stops monitoring controller's connections and disconnections
/// </summary>
public void Stop()
{
if (_watcher != null)
{
_watcher.MotionControllerAdded -= _watcher_MotionControllerAdded;
_watcher.MotionControllerRemoved -= _watcher_MotionControllerRemoved;
_watcher.Stop();
}
}
/// <summary>
/// called when a motion controller has been removed from the system:
/// Remove a motion controller from the cache
/// </summary>
/// <param name="sender">motion controller watcher</param>
/// <param name="e">motion controller </param>
private void _watcher_MotionControllerRemoved(object sender, MotionController e)
{
lock (_controllers)
{
_controllers.Remove(e.Handedness);
}
}
/// <summary>
/// called when a motion controller has been added to the system:
/// Remove a motion controller from the cache
/// </summary>
/// <param name="sender">motion controller watcher</param>
/// <param name="e">motion controller </param>
private void _watcher_MotionControllerAdded(object sender, MotionController e)
{
lock (_controllers)
{
_controllers[e.Handedness] = new MotionControllerState(e);
}
}
}
Reading new inputs by polling
You can read the current state of each known controller through MotionController.TryGetReadingAtTime during the Update method of the MonoBehavior class. You want to pass DateTime.Now as the timestamp parameter to ensure that the latest state of the controller is read.
public class MotionControllerStateCache : MonoBehaviour
{
…
private class MotionControllerState
{
…
/// <summary>
/// Update the current state of the motion controller
/// </summary>
/// <param name="when">time of the reading</param>
public void Update(DateTime when)
{
this.CurrentReading = this.MotionController.TryGetReadingAtTime(when);
}
/// <summary>
/// Last reading from the controller
/// </summary>
public MotionControllerReading CurrentReading { get; private set; }
}
/// <summary>
/// Updates the input states of the known motion controllers
/// </summary>
public void Update()
{
var now = DateTime.Now;
lock (_controllers)
{
foreach (var controller in _controllers)
{
controller.Value.Update(now);
}
}
}
}
You can grab the controllers current input value using the Handedness of the controller:
public class MotionControllerStateCache : MonoBehaviour
{
…
/// <summary>
/// Returns the current value of a controller input such as button or trigger
/// </summary>
/// <param name="handedness">Handedness of the controller</param>
/// <param name="input">Button or Trigger to query</param>
/// <returns>float value between 0.0 (not pressed) and 1.0
/// (fully pressed)</returns>
public float GetValue(Handedness handedness, ControllerInput input)
{
MotionControllerReading currentReading = null;
lock (_controllers)
{
if (_controllers.TryGetValue(handedness, out MotionControllerState mc))
{
currentReading = mc.CurrentReading;
}
}
return (currentReading == null) ? 0.0f : currentReading.GetPressedValue(input);
}
/// <summary>
/// Returns the current value of a controller input such as button or trigger
/// </summary>
/// <param name="handedness">Handedness of the controller</param>
/// <param name="input">Button or Trigger to query</param>
/// <returns>float value between 0.0 (not pressed) and 1.0
/// (fully pressed)</returns>
public float GetValue(UnityEngine.XR.WSA.Input.InteractionSourceHandedness handedness, ControllerInput input)
{
return GetValue(Convert(handedness), input);
}
/// <summary>
/// Returns a boolean indicating whether a controller input such as button or trigger is pressed
/// </summary>
/// <param name="handedness">Handedness of the controller</param>
/// <param name="input">Button or Trigger to query</param>
/// <returns>true if pressed, false if not pressed</returns>
public bool IsPressed(Handedness handedness, ControllerInput input)
{
return GetValue(handedness, input) >= PressedThreshold;
}
}
For example, to read the analog grasp value of an InteractionSource:
/// Read the analog grasp value of all connected interaction sources
void Update()
{
…
var stateCache = gameObject.GetComponent<MotionControllerStateCache>();
foreach (var sourceState in InteractionManager.GetCurrentReading())
{
float graspValue = stateCache.GetValue(sourceState.source.handedness,
Microsoft.MixedReality.Input.ControllerInput.Grasp);
…
}
}
Generating events from the new inputs
Instead of polling for a controller's state once per frame, you have the option of handling all state changes as events, which lets you handle even the quickest actions lasting less than a frame. In order for this approach to work, the cache of motion controllers needs to process all states published by a controller since the last frame, which you can do by storing the timestamp of the last MotionControllerReading retrieved from a MotionController and calling MotionController.TryGetReadingAfterTime():
private class MotionControllerState
{
…
/// <summary>
/// Returns an array representng buttons which are pressed
/// </summary>
/// <param name="reading">motion controller reading</param>
/// <returns>array of booleans</returns>
private bool[] GetPressed(MotionControllerReading reading)
{
if (reading == null)
{
return null;
}
else
{
bool[] ret = new bool[this.pressableInputs.Length];
for (int i = 0; i < pressableInputs.Length; ++i)
{
ret[i] = reading.GetPressedValue(pressableInputs[i]) >= PressedThreshold;
}
return ret;
}
}
/// <summary>
/// Get the next available state of the motion controller
/// </summary>
/// <param name="lastReading">previous reading</param>
/// <param name="newReading">new reading</param>
/// <returns>true is a new reading was available</returns>
private bool GetNextReading(MotionControllerReading lastReading, out MotionControllerReading newReading)
{
if (lastReading == null)
{
// Get the first state published by the controller
newReading = this.MotionController.TryGetReadingAfterSystemRelativeTime(TimeSpan.FromSeconds(0.0));
}
else
{
// Get the next state published by the controller
newReading = this.MotionController.TryGetReadingAfterTime(lastReading.InputTime);
}
return newReading != null;
}
/// <summary>
/// Processes all the new states published by the controller since the last call
/// </summary>
public IEnumerable<MotionControllerEventArgs> GetNextEvents()
{
MotionControllerReading lastReading = this.CurrentReading;
bool[] lastPressed = GetPressed(lastReading);
MotionControllerReading newReading;
bool[] newPressed;
while (GetNextReading(lastReading, out newReading))
{
newPressed = GetPressed(newReading);
// If we have two readings, compare and generate events
if (lastPressed != null)
{
for (int i = 0; i < pressableInputs.Length; ++i)
{
if (newPressed[i] != lastPressed[i])
{
yield return new MotionControllerEventArgs(this.MotionController.Handedness, newPressed[i], this.pressableInputs[i], newReading.InputTime);
}
}
}
lastPressed = newPressed;
lastReading = newReading;
}
// No more reading
this.CurrentReading = lastReading;
}
}
Now that you've updated the cache internal classes, the MonoBehavior class can expose two events – Pressed and Released – and raise them from its Update() method:
/// <summary>
/// Event argument class for InputPressed and InputReleased events
/// </summary>
public class MotionControllerEventArgs : EventArgs
{
public MotionControllerEventArgs(Handedness handedness, bool isPressed, rollerInput input, DateTime inputTime)
{
this.Handedness = handedness;
this.Input = input;
this.InputTime = inputTime;
this.IsPressed = isPressed;
}
/// <summary>
/// Handedness of the controller raising the event
/// </summary>
public Handedness Handedness { get; private set; }
/// <summary>
/// Button pressed or released
/// </summary>
public ControllerInput Input { get; private set; }
/// <summary>
/// Time of the event
/// </summary>
public DateTime InputTime { get; private set; }
/// <summary>
/// true if button is pressed, false otherwise
/// </summary>
public bool IsPressed { get; private set; }
}
/// <summary>
/// Event raised when a button is pressed
/// </summary>
public event EventHandler<MotionControllerEventArgs> InputPressed;
/// <summary>
/// Event raised when a button is released
/// </summary>
public event EventHandler<MotionControllerEventArgs> InputReleased;
/// <summary>
/// Updates the input states of the known motion controllers
/// </summary>
public void Update()
{
// If some event handler has been registered, we need to process all states
// since the last update, to avoid missing a quick press / release
if ((InputPressed != null) || (InputReleased != null))
{
List<MotionControllerEventArgs> events = new <MotionControllerEventArgs>();
lock (_controllers)
{
foreach (var controller in _controllers)
{
events.AddRange(controller.Value.GetNextEvents());
}
}
// Sort the events by time
events.Sort((e1, e2) => DateTime.Compare(e1.InputTime, e2.InputTime));
foreach (MotionControllerEventArgs evt in events)
{
if (evt.IsPressed && (InputPressed != null))
{
InputPressed(this, evt);
}
else if (!evt.IsPressed && (InputReleased != null))
{
InputReleased(this, evt);
}
}
}
else
{
// As we do not predict button presses and the timestamp of the next e is in the future
// DateTime.Now is correct in this context as it will return the latest e of controllers
// which is the best we have at the moment for the frame.
var now = DateTime.Now;
lock (_controllers)
{
foreach (var controller in _controllers)
{
controller.Value.Update(now);
}
}
}
}
The structure in the above code examples makes registering events much more readable:
public InteractionSourceHandedness handedness;
public Microsoft.MixedReality.Input.ControllerInput redButton;
// Start of the Mono Behavior: register handlers for events from cache
void Start()
{
var stateCache = gameObject.GetComponent<MotionControllerStateCache>();
stateCache.InputPressed += stateCache_InputPressed;
stateCache.InputReleased += stateCache_InputReleased;
…
}
// Called when a button is released
private void stateCache_InputReleased(object sender, MotionControllerStateCache.MotionControllerEventArgs e)
{
if ((e.SourceHandedness == handedness) && (e.Input == redButton))
{
…
}
}
// Called when a button is pressed
private void stateCache_InputPressed(object sender, MotionControllerStateCache.MotionControllerEventArgs e)
{
if ((e.SourceHandedness == handedness) && (e.Input == redButton))
{
…
}
}
See also
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