Implement a second order integrating VT strategy. (a5b06982) · Commits · e / os / android_frameworks_base

include/androidfw/VelocityTracker.h

+9 −7

Original line number	Original line	Diff line number	Diff line
	@@ -196,7 +196,8 @@ private:
	*/		*/
	class IntegratingVelocityTrackerStrategy : public VelocityTrackerStrategy {		class IntegratingVelocityTrackerStrategy : public VelocityTrackerStrategy {
	public:		public:
	IntegratingVelocityTrackerStrategy();		// Degree must be 1 or 2.
			IntegratingVelocityTrackerStrategy(uint32_t degree);
	~IntegratingVelocityTrackerStrategy();		~IntegratingVelocityTrackerStrategy();

	virtual void clear();		virtual void clear();
	@@ -209,18 +210,19 @@ private:
	// Current state estimate for a particular pointer.		// Current state estimate for a particular pointer.
	struct State {		struct State {
	nsecs_t updateTime;		nsecs_t updateTime;
	bool first;		uint32_t degree;

	float xpos, xvel;		float xpos, xvel, xaccel;
	float ypos, yvel;		float ypos, yvel, yaccel;
	};		};

			const uint32_t mDegree;
	BitSet32 mPointerIdBits;		BitSet32 mPointerIdBits;
	State mPointerState[MAX_POINTER_ID + 1];		State mPointerState[MAX_POINTER_ID + 1];

	static void initState(State& state, nsecs_t eventTime, float xpos, float ypos);		void initState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
	static void updateState(State& state, nsecs_t eventTime, float xpos, float ypos);		void updateState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
	static void populateEstimator(const State& state, VelocityTracker::Estimator* outEstimator);		void populateEstimator(const State& state, VelocityTracker::Estimator* outEstimator) const;
	};		};

	} // namespace android		} // namespace android

libs/androidfw/VelocityTracker.cpp

+37 −11

Original line number	Original line	Diff line number	Diff line
	@@ -182,7 +182,13 @@ VelocityTrackerStrategy* VelocityTracker::createStrategy(const char* strategy) {
	// more tolerant of errors. Like 'lsq1', this strategy tends to underestimate		// more tolerant of errors. Like 'lsq1', this strategy tends to underestimate
	// the velocity of a fling but this strategy tends to respond to changes in		// the velocity of a fling but this strategy tends to respond to changes in
	// direction more quickly and accurately.		// direction more quickly and accurately.
	return new IntegratingVelocityTrackerStrategy();		return new IntegratingVelocityTrackerStrategy(1);
			}
			if (!strcmp("int2", strategy)) {
			// 2nd order integrating filter. Quality: EXPERIMENTAL.
			// For comparison purposes only. Unlike 'int1' this strategy can compensate
			// for acceleration but it typically overestimates the effect.
			return new IntegratingVelocityTrackerStrategy(2);
	}		}
	return NULL;		return NULL;
	}		}
	@@ -680,7 +686,8 @@ float LeastSquaresVelocityTrackerStrategy::chooseWeight(uint32_t index) const {

	// --- IntegratingVelocityTrackerStrategy ---		// --- IntegratingVelocityTrackerStrategy ---

	IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy() {		IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy(uint32_t degree) :
			mDegree(degree) {
	}		}

	IntegratingVelocityTrackerStrategy::~IntegratingVelocityTrackerStrategy() {		IntegratingVelocityTrackerStrategy::~IntegratingVelocityTrackerStrategy() {
	@@ -725,18 +732,20 @@ bool IntegratingVelocityTrackerStrategy::getEstimator(uint32_t id,
	}		}

	void IntegratingVelocityTrackerStrategy::initState(State& state,		void IntegratingVelocityTrackerStrategy::initState(State& state,
	nsecs_t eventTime, float xpos, float ypos) {		nsecs_t eventTime, float xpos, float ypos) const {
	state.updateTime = eventTime;		state.updateTime = eventTime;
	state.first = true;		state.degree = 0;

	state.xpos = xpos;		state.xpos = xpos;
	state.xvel = 0;		state.xvel = 0;
			state.xaccel = 0;
	state.ypos = ypos;		state.ypos = ypos;
	state.yvel = 0;		state.yvel = 0;
			state.yaccel = 0;
	}		}

	void IntegratingVelocityTrackerStrategy::updateState(State& state,		void IntegratingVelocityTrackerStrategy::updateState(State& state,
	nsecs_t eventTime, float xpos, float ypos) {		nsecs_t eventTime, float xpos, float ypos) const {
	const nsecs_t MIN_TIME_DELTA = 2 * NANOS_PER_MS;		const nsecs_t MIN_TIME_DELTA = 2 * NANOS_PER_MS;
	const float FILTER_TIME_CONSTANT = 0.010f; // 10 milliseconds		const float FILTER_TIME_CONSTANT = 0.010f; // 10 milliseconds

	@@ -749,28 +758,45 @@ void IntegratingVelocityTrackerStrategy::updateState(State& state,

	float xvel = (xpos - state.xpos) / dt;		float xvel = (xpos - state.xpos) / dt;
	float yvel = (ypos - state.ypos) / dt;		float yvel = (ypos - state.ypos) / dt;
	if (state.first) {		if (state.degree == 0) {
	state.xvel = xvel;		state.xvel = xvel;
	state.yvel = yvel;		state.yvel = yvel;
	state.first = false;		state.degree = 1;
	} else {		} else {
	float alpha = dt / (FILTER_TIME_CONSTANT + dt);		float alpha = dt / (FILTER_TIME_CONSTANT + dt);
			if (mDegree == 1) {
	state.xvel += (xvel - state.xvel) * alpha;		state.xvel += (xvel - state.xvel) * alpha;
	state.yvel += (yvel - state.yvel) * alpha;		state.yvel += (yvel - state.yvel) * alpha;
			} else {
			float xaccel = (xvel - state.xvel) / dt;
			float yaccel = (yvel - state.yvel) / dt;
			if (state.degree == 1) {
			state.xaccel = xaccel;
			state.yaccel = yaccel;
			state.degree = 2;
			} else {
			state.xaccel += (xaccel - state.xaccel) * alpha;
			state.yaccel += (yaccel - state.yaccel) * alpha;
			}
			state.xvel += (state.xaccel * dt) * alpha;
			state.yvel += (state.yaccel * dt) * alpha;
			}
	}		}
	state.xpos = xpos;		state.xpos = xpos;
	state.ypos = ypos;		state.ypos = ypos;
	}		}

	void IntegratingVelocityTrackerStrategy::populateEstimator(const State& state,		void IntegratingVelocityTrackerStrategy::populateEstimator(const State& state,
	VelocityTracker::Estimator* outEstimator) {		VelocityTracker::Estimator* outEstimator) const {
	outEstimator->time = state.updateTime;		outEstimator->time = state.updateTime;
	outEstimator->degree = 1;
	outEstimator->confidence = 1.0f;		outEstimator->confidence = 1.0f;
			outEstimator->degree = state.degree;
	outEstimator->xCoeff[0] = state.xpos;		outEstimator->xCoeff[0] = state.xpos;
	outEstimator->xCoeff[1] = state.xvel;		outEstimator->xCoeff[1] = state.xvel;
			outEstimator->xCoeff[2] = state.xaccel / 2;
	outEstimator->yCoeff[0] = state.ypos;		outEstimator->yCoeff[0] = state.ypos;
	outEstimator->yCoeff[1] = state.yvel;		outEstimator->yCoeff[1] = state.yvel;
			outEstimator->yCoeff[2] = state.yaccel / 2;
	}		}

	} // namespace android		} // namespace android