addGyroscope method

bool addGyroscope(double x, double y, int timestampUs)

Uses acquisition time, never callback delivery time. Duplicate/out-of- order samples are ignored; gaps over 250 ms restart integration instead of extrapolating a resumed sensor across an unknown interval.

Implementation

bool addGyroscope(double x, double y, int timestampUs) {
  dYaw = 0;
  dPitch = 0;
  absolutePitch = null;
  if (!x.isFinite || !y.isFinite) return false;
  final previous = _lastTimestampUs;
  if (previous != null && timestampUs <= previous) return false;
  if (previous != null && timestampUs - previous > 250000) reset();

  if (gravityPitch != null && !_hasPitchReference) {
    _pitch = gravityPitch!;
    _previousPitch = (_pitch * pitchGain).clamp(-1.45, 1.45);
    _hasPitchReference = true;
  }
  if (_lastTimestampUs == null) {
    _lastTimestampUs = timestampUs;
    if (_hasPitchReference) {
      absolutePitch = (_pitch * pitchGain).clamp(-1.45, 1.45);
    }
    return absolutePitch != null;
  }
  final dt = (timestampUs - _lastTimestampUs!) / 1000000;
  _lastTimestampUs = timestampUs;

  // A low angular velocity is not evidence of rest. Bias changes only via
  // explicit stationary calibration, so slow intentional turns survive.
  var gx = x - offsetX;
  var gy = y - offsetY;
  if (gx.abs() < 0.002) gx = 0;
  if (gy.abs() < 0.002) gy = 0;
  _yaw += gx * dt;
  _pitch += gy * dt;
  if (_hasPitchReference) {
    // Equivalent to alpha=.98 at 100 Hz, independent of sensor frequency.
    final alpha = pow(0.98, dt * 100).toDouble();
    _pitch = alpha * _pitch + (1 - alpha) * gravityPitch!;
  }

  final prediction = predictionMs / 1000;
  final yaw = _yaw + gx * prediction;
  final pitch = ((_pitch + gy * prediction) * pitchGain).clamp(-1.45, 1.45);
  final rawYaw = yaw - _previousYaw;
  final rawPitch = pitch - _previousPitch;
  _previousYaw = yaw;
  _previousPitch = pitch;
  if (jitterDamping) {
    // Smooth without a per-frame deadband: that would erase slow motion
    // increasingly often as a device's sampling frequency increases.
    _dampedYaw = _dampedYaw * 0.15 + rawYaw * 0.85;
    _dampedPitch = _dampedPitch * 0.15 + rawPitch * 0.85;
    dYaw = _dampedYaw * sensitivity;
    dPitch = _dampedPitch * sensitivity;
  } else {
    dYaw = rawYaw * sensitivity;
    dPitch = rawPitch * sensitivity;
  }
  if (_hasPitchReference) {
    absolutePitch = pitch;
    dPitch = 0;
  }
  return true;
}