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Implement a second order integrating VT strategy.

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Bug: 6413587
Change-Id: I51bc7b8cbff22b10b728fc84ee15370e9984dd55
This commit is contained in:
Jeff Brown
2012-06-03 22:46:07 -07:00
parent 18f329e948
commit a5b0698231
2 changed files with 46 additions and 18 deletions
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16
include/androidfw/VelocityTracker.h
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@@ -196,7 +196,8 @@ private:
*/
class IntegratingVelocityTrackerStrategy : public VelocityTrackerStrategy {
public:
IntegratingVelocityTrackerStrategy();
// Degree must be 1 or 2.
IntegratingVelocityTrackerStrategy(uint32_t degree);
~IntegratingVelocityTrackerStrategy();
virtual void clear();
@@ -209,18 +210,19 @@ private:
// Current state estimate for a particular pointer.
struct State {
nsecs_t updateTime;
bool first;
uint32_t degree;
float xpos, xvel;
float ypos, yvel;
float xpos, xvel, xaccel;
float ypos, yvel, yaccel;
};
const uint32_t mDegree;
BitSet32 mPointerIdBits;
State mPointerState[MAX_POINTER_ID + 1];
static void initState(State& state, nsecs_t eventTime, float xpos, float ypos);
static void updateState(State& state, nsecs_t eventTime, float xpos, float ypos);
static void populateEstimator(const State& state, VelocityTracker::Estimator* outEstimator);
void initState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
void updateState(State& state, nsecs_t eventTime, float xpos, float ypos) const;
void populateEstimator(const State& state, VelocityTracker::Estimator* outEstimator) const;
};
} // namespace android

48
libs/androidfw/VelocityTracker.cpp
View File

@@ -182,7 +182,13 @@ VelocityTrackerStrategy* VelocityTracker::createStrategy(const char* strategy) {
// 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
// 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;
}
@@ -680,7 +686,8 @@ float LeastSquaresVelocityTrackerStrategy::chooseWeight(uint32_t index) const {
// --- IntegratingVelocityTrackerStrategy ---
IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy() {
IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy(uint32_t degree) :
mDegree(degree) {
}
IntegratingVelocityTrackerStrategy::~IntegratingVelocityTrackerStrategy() {
@@ -725,18 +732,20 @@ bool IntegratingVelocityTrackerStrategy::getEstimator(uint32_t id,
}
void IntegratingVelocityTrackerStrategy::initState(State& state,
nsecs_t eventTime, float xpos, float ypos) {
nsecs_t eventTime, float xpos, float ypos) const {
state.updateTime = eventTime;
state.first = true;
state.degree = 0;
state.xpos = xpos;
state.xvel = 0;
state.xaccel = 0;
state.ypos = ypos;
state.yvel = 0;
state.yaccel = 0;
}
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 float FILTER_TIME_CONSTANT = 0.010f; // 10 milliseconds
@@ -749,28 +758,45 @@ void IntegratingVelocityTrackerStrategy::updateState(State& state,
float xvel = (xpos - state.xpos) / dt;
float yvel = (ypos - state.ypos) / dt;
if (state.first) {
if (state.degree == 0) {
state.xvel = xvel;
state.yvel = yvel;
state.first = false;
state.degree = 1;
} else {
float alpha = dt / (FILTER_TIME_CONSTANT + dt);
state.xvel += (xvel - state.xvel) * alpha;
state.yvel += (yvel - state.yvel) * alpha;
if (mDegree == 1) {
state.xvel += (xvel - state.xvel) * 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.ypos = ypos;
}
void IntegratingVelocityTrackerStrategy::populateEstimator(const State& state,
VelocityTracker::Estimator* outEstimator) {
VelocityTracker::Estimator* outEstimator) const {
outEstimator->time = state.updateTime;
outEstimator->degree = 1;
outEstimator->confidence = 1.0f;
outEstimator->degree = state.degree;
outEstimator->xCoeff[0] = state.xpos;
outEstimator->xCoeff[1] = state.xvel;
outEstimator->xCoeff[2] = state.xaccel / 2;
outEstimator->yCoeff[0] = state.ypos;
outEstimator->yCoeff[1] = state.yvel;
outEstimator->yCoeff[2] = state.yaccel / 2;
}
} // namespace android