зеркало из https://github.com/mozilla/gecko-dev.git
930 строки
32 KiB
C++
930 строки
32 KiB
C++
/*
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* Copyright (C) 2012 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#define LOG_TAG "VelocityTracker"
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//#define LOG_NDEBUG 0
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#include "cutils_log.h"
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// Log debug messages about velocity tracking.
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#define DEBUG_VELOCITY 0
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// Log debug messages about the progress of the algorithm itself.
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#define DEBUG_STRATEGY 0
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#include <math.h>
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#include <limits.h>
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#include "VelocityTracker.h"
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#include <utils/BitSet.h>
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#include <utils/String8.h>
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#include <utils/Timers.h>
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#include <cutils/properties.h>
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namespace android {
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// Nanoseconds per milliseconds.
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static const nsecs_t NANOS_PER_MS = 1000000;
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// Threshold for determining that a pointer has stopped moving.
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// Some input devices do not send ACTION_MOVE events in the case where a pointer has
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// stopped. We need to detect this case so that we can accurately predict the
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// velocity after the pointer starts moving again.
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static const nsecs_t ASSUME_POINTER_STOPPED_TIME = 40 * NANOS_PER_MS;
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static float vectorDot(const float* a, const float* b, uint32_t m) {
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float r = 0;
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while (m--) {
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r += *(a++) * *(b++);
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}
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return r;
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}
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static float vectorNorm(const float* a, uint32_t m) {
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float r = 0;
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while (m--) {
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float t = *(a++);
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r += t * t;
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}
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return sqrtf(r);
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}
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#if DEBUG_STRATEGY || DEBUG_VELOCITY
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static String8 vectorToString(const float* a, uint32_t m) {
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String8 str;
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str.append("[");
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while (m--) {
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str.appendFormat(" %f", *(a++));
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if (m) {
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str.append(",");
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}
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}
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str.append(" ]");
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return str;
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}
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static String8 matrixToString(const float* a, uint32_t m, uint32_t n, bool rowMajor) {
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String8 str;
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str.append("[");
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for (size_t i = 0; i < m; i++) {
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if (i) {
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str.append(",");
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}
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str.append(" [");
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for (size_t j = 0; j < n; j++) {
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if (j) {
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str.append(",");
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}
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str.appendFormat(" %f", a[rowMajor ? i * n + j : j * m + i]);
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}
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str.append(" ]");
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}
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str.append(" ]");
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return str;
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}
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#endif
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// --- VelocityTracker ---
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// The default velocity tracker strategy.
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// Although other strategies are available for testing and comparison purposes,
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// this is the strategy that applications will actually use. Be very careful
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// when adjusting the default strategy because it can dramatically affect
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// (often in a bad way) the user experience.
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const char* VelocityTracker::DEFAULT_STRATEGY = "lsq2";
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VelocityTracker::VelocityTracker(const char* strategy) :
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mLastEventTime(0), mCurrentPointerIdBits(0), mActivePointerId(-1) {
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char value[PROPERTY_VALUE_MAX];
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// Allow the default strategy to be overridden using a system property for debugging.
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if (!strategy) {
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int length = property_get("debug.velocitytracker.strategy", value, NULL);
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if (length > 0) {
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strategy = value;
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} else {
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strategy = DEFAULT_STRATEGY;
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}
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}
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// Configure the strategy.
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if (!configureStrategy(strategy)) {
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ALOGD("Unrecognized velocity tracker strategy name '%s'.", strategy);
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if (!configureStrategy(DEFAULT_STRATEGY)) {
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LOG_ALWAYS_FATAL("Could not create the default velocity tracker strategy '%s'!",
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strategy);
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}
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}
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}
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VelocityTracker::~VelocityTracker() {
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delete mStrategy;
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}
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bool VelocityTracker::configureStrategy(const char* strategy) {
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mStrategy = createStrategy(strategy);
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return mStrategy != NULL;
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}
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VelocityTrackerStrategy* VelocityTracker::createStrategy(const char* strategy) {
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if (!strcmp("lsq1", strategy)) {
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// 1st order least squares. Quality: POOR.
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// Frequently underfits the touch data especially when the finger accelerates
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// or changes direction. Often underestimates velocity. The direction
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// is overly influenced by historical touch points.
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return new LeastSquaresVelocityTrackerStrategy(1);
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}
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if (!strcmp("lsq2", strategy)) {
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// 2nd order least squares. Quality: VERY GOOD.
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// Pretty much ideal, but can be confused by certain kinds of touch data,
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// particularly if the panel has a tendency to generate delayed,
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// duplicate or jittery touch coordinates when the finger is released.
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return new LeastSquaresVelocityTrackerStrategy(2);
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}
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if (!strcmp("lsq3", strategy)) {
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// 3rd order least squares. Quality: UNUSABLE.
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// Frequently overfits the touch data yielding wildly divergent estimates
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// of the velocity when the finger is released.
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return new LeastSquaresVelocityTrackerStrategy(3);
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}
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if (!strcmp("wlsq2-delta", strategy)) {
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// 2nd order weighted least squares, delta weighting. Quality: EXPERIMENTAL
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return new LeastSquaresVelocityTrackerStrategy(2,
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LeastSquaresVelocityTrackerStrategy::WEIGHTING_DELTA);
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}
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if (!strcmp("wlsq2-central", strategy)) {
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// 2nd order weighted least squares, central weighting. Quality: EXPERIMENTAL
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return new LeastSquaresVelocityTrackerStrategy(2,
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LeastSquaresVelocityTrackerStrategy::WEIGHTING_CENTRAL);
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}
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if (!strcmp("wlsq2-recent", strategy)) {
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// 2nd order weighted least squares, recent weighting. Quality: EXPERIMENTAL
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return new LeastSquaresVelocityTrackerStrategy(2,
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LeastSquaresVelocityTrackerStrategy::WEIGHTING_RECENT);
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}
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if (!strcmp("int1", strategy)) {
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// 1st order integrating filter. Quality: GOOD.
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// Not as good as 'lsq2' because it cannot estimate acceleration but it is
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// more tolerant of errors. Like 'lsq1', this strategy tends to underestimate
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// the velocity of a fling but this strategy tends to respond to changes in
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// direction more quickly and accurately.
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return new IntegratingVelocityTrackerStrategy(1);
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}
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if (!strcmp("int2", strategy)) {
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// 2nd order integrating filter. Quality: EXPERIMENTAL.
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// For comparison purposes only. Unlike 'int1' this strategy can compensate
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// for acceleration but it typically overestimates the effect.
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return new IntegratingVelocityTrackerStrategy(2);
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}
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if (!strcmp("legacy", strategy)) {
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// Legacy velocity tracker algorithm. Quality: POOR.
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// For comparison purposes only. This algorithm is strongly influenced by
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// old data points, consistently underestimates velocity and takes a very long
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// time to adjust to changes in direction.
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return new LegacyVelocityTrackerStrategy();
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}
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return NULL;
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}
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void VelocityTracker::clear() {
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mCurrentPointerIdBits.clear();
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mActivePointerId = -1;
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mStrategy->clear();
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}
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void VelocityTracker::clearPointers(BitSet32 idBits) {
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BitSet32 remainingIdBits(mCurrentPointerIdBits.value & ~idBits.value);
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mCurrentPointerIdBits = remainingIdBits;
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if (mActivePointerId >= 0 && idBits.hasBit(mActivePointerId)) {
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mActivePointerId = !remainingIdBits.isEmpty() ? remainingIdBits.firstMarkedBit() : -1;
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}
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mStrategy->clearPointers(idBits);
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}
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void VelocityTracker::addMovement(nsecs_t eventTime, BitSet32 idBits, const Position* positions) {
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while (idBits.count() > MAX_POINTERS) {
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idBits.clearLastMarkedBit();
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}
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if ((mCurrentPointerIdBits.value & idBits.value)
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&& eventTime >= mLastEventTime + ASSUME_POINTER_STOPPED_TIME) {
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#if DEBUG_VELOCITY
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ALOGD("VelocityTracker: stopped for %0.3f ms, clearing state.",
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(eventTime - mLastEventTime) * 0.000001f);
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#endif
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// We have not received any movements for too long. Assume that all pointers
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// have stopped.
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mStrategy->clear();
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}
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mLastEventTime = eventTime;
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mCurrentPointerIdBits = idBits;
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if (mActivePointerId < 0 || !idBits.hasBit(mActivePointerId)) {
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mActivePointerId = idBits.isEmpty() ? -1 : idBits.firstMarkedBit();
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}
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mStrategy->addMovement(eventTime, idBits, positions);
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#if DEBUG_VELOCITY
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ALOGD("VelocityTracker: addMovement eventTime=%lld, idBits=0x%08x, activePointerId=%d",
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eventTime, idBits.value, mActivePointerId);
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for (BitSet32 iterBits(idBits); !iterBits.isEmpty(); ) {
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uint32_t id = iterBits.firstMarkedBit();
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uint32_t index = idBits.getIndexOfBit(id);
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iterBits.clearBit(id);
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Estimator estimator;
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getEstimator(id, &estimator);
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ALOGD(" %d: position (%0.3f, %0.3f), "
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"estimator (degree=%d, xCoeff=%s, yCoeff=%s, confidence=%f)",
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id, positions[index].x, positions[index].y,
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int(estimator.degree),
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vectorToString(estimator.xCoeff, estimator.degree + 1).string(),
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vectorToString(estimator.yCoeff, estimator.degree + 1).string(),
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estimator.confidence);
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}
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#endif
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}
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void VelocityTracker::addMovement(const MotionEvent* event) {
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int32_t actionMasked = event->getActionMasked();
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switch (actionMasked) {
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case AMOTION_EVENT_ACTION_DOWN:
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case AMOTION_EVENT_ACTION_HOVER_ENTER:
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// Clear all pointers on down before adding the new movement.
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clear();
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break;
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case AMOTION_EVENT_ACTION_POINTER_DOWN: {
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// Start a new movement trace for a pointer that just went down.
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// We do this on down instead of on up because the client may want to query the
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// final velocity for a pointer that just went up.
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BitSet32 downIdBits;
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downIdBits.markBit(event->getPointerId(event->getActionIndex()));
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clearPointers(downIdBits);
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break;
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}
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case AMOTION_EVENT_ACTION_MOVE:
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case AMOTION_EVENT_ACTION_HOVER_MOVE:
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break;
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default:
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// Ignore all other actions because they do not convey any new information about
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// pointer movement. We also want to preserve the last known velocity of the pointers.
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// Note that ACTION_UP and ACTION_POINTER_UP always report the last known position
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// of the pointers that went up. ACTION_POINTER_UP does include the new position of
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// pointers that remained down but we will also receive an ACTION_MOVE with this
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// information if any of them actually moved. Since we don't know how many pointers
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// will be going up at once it makes sense to just wait for the following ACTION_MOVE
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// before adding the movement.
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return;
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}
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size_t pointerCount = event->getPointerCount();
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if (pointerCount > MAX_POINTERS) {
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pointerCount = MAX_POINTERS;
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}
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BitSet32 idBits;
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for (size_t i = 0; i < pointerCount; i++) {
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idBits.markBit(event->getPointerId(i));
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}
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uint32_t pointerIndex[MAX_POINTERS];
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for (size_t i = 0; i < pointerCount; i++) {
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pointerIndex[i] = idBits.getIndexOfBit(event->getPointerId(i));
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}
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nsecs_t eventTime;
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Position positions[pointerCount];
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size_t historySize = event->getHistorySize();
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for (size_t h = 0; h < historySize; h++) {
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eventTime = event->getHistoricalEventTime(h);
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for (size_t i = 0; i < pointerCount; i++) {
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uint32_t index = pointerIndex[i];
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positions[index].x = event->getHistoricalX(i, h);
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positions[index].y = event->getHistoricalY(i, h);
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}
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addMovement(eventTime, idBits, positions);
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}
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eventTime = event->getEventTime();
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for (size_t i = 0; i < pointerCount; i++) {
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uint32_t index = pointerIndex[i];
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positions[index].x = event->getX(i);
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positions[index].y = event->getY(i);
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}
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addMovement(eventTime, idBits, positions);
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}
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bool VelocityTracker::getVelocity(uint32_t id, float* outVx, float* outVy) const {
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Estimator estimator;
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if (getEstimator(id, &estimator) && estimator.degree >= 1) {
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*outVx = estimator.xCoeff[1];
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*outVy = estimator.yCoeff[1];
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return true;
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}
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*outVx = 0;
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*outVy = 0;
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return false;
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}
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bool VelocityTracker::getEstimator(uint32_t id, Estimator* outEstimator) const {
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return mStrategy->getEstimator(id, outEstimator);
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}
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// --- LeastSquaresVelocityTrackerStrategy ---
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const nsecs_t LeastSquaresVelocityTrackerStrategy::HORIZON;
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const uint32_t LeastSquaresVelocityTrackerStrategy::HISTORY_SIZE;
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LeastSquaresVelocityTrackerStrategy::LeastSquaresVelocityTrackerStrategy(
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uint32_t degree, Weighting weighting) :
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mDegree(degree), mWeighting(weighting) {
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clear();
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}
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LeastSquaresVelocityTrackerStrategy::~LeastSquaresVelocityTrackerStrategy() {
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}
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void LeastSquaresVelocityTrackerStrategy::clear() {
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mIndex = 0;
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mMovements[0].idBits.clear();
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}
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void LeastSquaresVelocityTrackerStrategy::clearPointers(BitSet32 idBits) {
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BitSet32 remainingIdBits(mMovements[mIndex].idBits.value & ~idBits.value);
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mMovements[mIndex].idBits = remainingIdBits;
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}
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void LeastSquaresVelocityTrackerStrategy::addMovement(nsecs_t eventTime, BitSet32 idBits,
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const VelocityTracker::Position* positions) {
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if (++mIndex == HISTORY_SIZE) {
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mIndex = 0;
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}
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Movement& movement = mMovements[mIndex];
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movement.eventTime = eventTime;
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movement.idBits = idBits;
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uint32_t count = idBits.count();
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for (uint32_t i = 0; i < count; i++) {
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movement.positions[i] = positions[i];
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}
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}
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/**
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* Solves a linear least squares problem to obtain a N degree polynomial that fits
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* the specified input data as nearly as possible.
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*
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* Returns true if a solution is found, false otherwise.
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*
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* The input consists of two vectors of data points X and Y with indices 0..m-1
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* along with a weight vector W of the same size.
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*
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* The output is a vector B with indices 0..n that describes a polynomial
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* that fits the data, such the sum of W[i] * W[i] * abs(Y[i] - (B[0] + B[1] X[i]
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* + B[2] X[i]^2 ... B[n] X[i]^n)) for all i between 0 and m-1 is minimized.
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*
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* Accordingly, the weight vector W should be initialized by the caller with the
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* reciprocal square root of the variance of the error in each input data point.
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* In other words, an ideal choice for W would be W[i] = 1 / var(Y[i]) = 1 / stddev(Y[i]).
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* The weights express the relative importance of each data point. If the weights are
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* all 1, then the data points are considered to be of equal importance when fitting
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* the polynomial. It is a good idea to choose weights that diminish the importance
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* of data points that may have higher than usual error margins.
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*
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* Errors among data points are assumed to be independent. W is represented here
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* as a vector although in the literature it is typically taken to be a diagonal matrix.
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*
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* That is to say, the function that generated the input data can be approximated
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* by y(x) ~= B[0] + B[1] x + B[2] x^2 + ... + B[n] x^n.
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*
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* The coefficient of determination (R^2) is also returned to describe the goodness
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* of fit of the model for the given data. It is a value between 0 and 1, where 1
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* indicates perfect correspondence.
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*
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* This function first expands the X vector to a m by n matrix A such that
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* A[i][0] = 1, A[i][1] = X[i], A[i][2] = X[i]^2, ..., A[i][n] = X[i]^n, then
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* multiplies it by w[i]./
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*
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* Then it calculates the QR decomposition of A yielding an m by m orthonormal matrix Q
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* and an m by n upper triangular matrix R. Because R is upper triangular (lower
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* part is all zeroes), we can simplify the decomposition into an m by n matrix
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* Q1 and a n by n matrix R1 such that A = Q1 R1.
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*
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* Finally we solve the system of linear equations given by R1 B = (Qtranspose W Y)
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* to find B.
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*
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* For efficiency, we lay out A and Q column-wise in memory because we frequently
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* operate on the column vectors. Conversely, we lay out R row-wise.
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*
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* http://en.wikipedia.org/wiki/Numerical_methods_for_linear_least_squares
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* http://en.wikipedia.org/wiki/Gram-Schmidt
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*/
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static bool solveLeastSquares(const float* x, const float* y,
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const float* w, uint32_t m, uint32_t n, float* outB, float* outDet) {
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#if DEBUG_STRATEGY
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ALOGD("solveLeastSquares: m=%d, n=%d, x=%s, y=%s, w=%s", int(m), int(n),
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vectorToString(x, m).string(), vectorToString(y, m).string(),
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vectorToString(w, m).string());
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#endif
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// Expand the X vector to a matrix A, pre-multiplied by the weights.
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float a[n][m]; // column-major order
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for (uint32_t h = 0; h < m; h++) {
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a[0][h] = w[h];
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for (uint32_t i = 1; i < n; i++) {
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a[i][h] = a[i - 1][h] * x[h];
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}
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}
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#if DEBUG_STRATEGY
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ALOGD(" - a=%s", matrixToString(&a[0][0], m, n, false /*rowMajor*/).string());
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#endif
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// Apply the Gram-Schmidt process to A to obtain its QR decomposition.
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float q[n][m]; // orthonormal basis, column-major order
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float r[n][n]; // upper triangular matrix, row-major order
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for (uint32_t j = 0; j < n; j++) {
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for (uint32_t h = 0; h < m; h++) {
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q[j][h] = a[j][h];
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}
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for (uint32_t i = 0; i < j; i++) {
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float dot = vectorDot(&q[j][0], &q[i][0], m);
|
|
for (uint32_t h = 0; h < m; h++) {
|
|
q[j][h] -= dot * q[i][h];
|
|
}
|
|
}
|
|
|
|
float norm = vectorNorm(&q[j][0], m);
|
|
if (norm < 0.000001f) {
|
|
// vectors are linearly dependent or zero so no solution
|
|
#if DEBUG_STRATEGY
|
|
ALOGD(" - no solution, norm=%f", norm);
|
|
#endif
|
|
return false;
|
|
}
|
|
|
|
float invNorm = 1.0f / norm;
|
|
for (uint32_t h = 0; h < m; h++) {
|
|
q[j][h] *= invNorm;
|
|
}
|
|
for (uint32_t i = 0; i < n; i++) {
|
|
r[j][i] = i < j ? 0 : vectorDot(&q[j][0], &a[i][0], m);
|
|
}
|
|
}
|
|
#if DEBUG_STRATEGY
|
|
ALOGD(" - q=%s", matrixToString(&q[0][0], m, n, false /*rowMajor*/).string());
|
|
ALOGD(" - r=%s", matrixToString(&r[0][0], n, n, true /*rowMajor*/).string());
|
|
|
|
// calculate QR, if we factored A correctly then QR should equal A
|
|
float qr[n][m];
|
|
for (uint32_t h = 0; h < m; h++) {
|
|
for (uint32_t i = 0; i < n; i++) {
|
|
qr[i][h] = 0;
|
|
for (uint32_t j = 0; j < n; j++) {
|
|
qr[i][h] += q[j][h] * r[j][i];
|
|
}
|
|
}
|
|
}
|
|
ALOGD(" - qr=%s", matrixToString(&qr[0][0], m, n, false /*rowMajor*/).string());
|
|
#endif
|
|
|
|
// Solve R B = Qt W Y to find B. This is easy because R is upper triangular.
|
|
// We just work from bottom-right to top-left calculating B's coefficients.
|
|
float wy[m];
|
|
for (uint32_t h = 0; h < m; h++) {
|
|
wy[h] = y[h] * w[h];
|
|
}
|
|
for (uint32_t i = n; i-- != 0; ) {
|
|
outB[i] = vectorDot(&q[i][0], wy, m);
|
|
for (uint32_t j = n - 1; j > i; j--) {
|
|
outB[i] -= r[i][j] * outB[j];
|
|
}
|
|
outB[i] /= r[i][i];
|
|
}
|
|
#if DEBUG_STRATEGY
|
|
ALOGD(" - b=%s", vectorToString(outB, n).string());
|
|
#endif
|
|
|
|
// Calculate the coefficient of determination as 1 - (SSerr / SStot) where
|
|
// SSerr is the residual sum of squares (variance of the error),
|
|
// and SStot is the total sum of squares (variance of the data) where each
|
|
// has been weighted.
|
|
float ymean = 0;
|
|
for (uint32_t h = 0; h < m; h++) {
|
|
ymean += y[h];
|
|
}
|
|
ymean /= m;
|
|
|
|
float sserr = 0;
|
|
float sstot = 0;
|
|
for (uint32_t h = 0; h < m; h++) {
|
|
float err = y[h] - outB[0];
|
|
float term = 1;
|
|
for (uint32_t i = 1; i < n; i++) {
|
|
term *= x[h];
|
|
err -= term * outB[i];
|
|
}
|
|
sserr += w[h] * w[h] * err * err;
|
|
float var = y[h] - ymean;
|
|
sstot += w[h] * w[h] * var * var;
|
|
}
|
|
*outDet = sstot > 0.000001f ? 1.0f - (sserr / sstot) : 1;
|
|
#if DEBUG_STRATEGY
|
|
ALOGD(" - sserr=%f", sserr);
|
|
ALOGD(" - sstot=%f", sstot);
|
|
ALOGD(" - det=%f", *outDet);
|
|
#endif
|
|
return true;
|
|
}
|
|
|
|
bool LeastSquaresVelocityTrackerStrategy::getEstimator(uint32_t id,
|
|
VelocityTracker::Estimator* outEstimator) const {
|
|
outEstimator->clear();
|
|
|
|
// Iterate over movement samples in reverse time order and collect samples.
|
|
float x[HISTORY_SIZE];
|
|
float y[HISTORY_SIZE];
|
|
float w[HISTORY_SIZE];
|
|
float time[HISTORY_SIZE];
|
|
uint32_t m = 0;
|
|
uint32_t index = mIndex;
|
|
const Movement& newestMovement = mMovements[mIndex];
|
|
do {
|
|
const Movement& movement = mMovements[index];
|
|
if (!movement.idBits.hasBit(id)) {
|
|
break;
|
|
}
|
|
|
|
nsecs_t age = newestMovement.eventTime - movement.eventTime;
|
|
if (age > HORIZON) {
|
|
break;
|
|
}
|
|
|
|
const VelocityTracker::Position& position = movement.getPosition(id);
|
|
x[m] = position.x;
|
|
y[m] = position.y;
|
|
w[m] = chooseWeight(index);
|
|
time[m] = -age * 0.000000001f;
|
|
index = (index == 0 ? HISTORY_SIZE : index) - 1;
|
|
} while (++m < HISTORY_SIZE);
|
|
|
|
if (m == 0) {
|
|
return false; // no data
|
|
}
|
|
|
|
// Calculate a least squares polynomial fit.
|
|
uint32_t degree = mDegree;
|
|
if (degree > m - 1) {
|
|
degree = m - 1;
|
|
}
|
|
if (degree >= 1) {
|
|
float xdet, ydet;
|
|
uint32_t n = degree + 1;
|
|
if (solveLeastSquares(time, x, w, m, n, outEstimator->xCoeff, &xdet)
|
|
&& solveLeastSquares(time, y, w, m, n, outEstimator->yCoeff, &ydet)) {
|
|
outEstimator->time = newestMovement.eventTime;
|
|
outEstimator->degree = degree;
|
|
outEstimator->confidence = xdet * ydet;
|
|
#if DEBUG_STRATEGY
|
|
ALOGD("estimate: degree=%d, xCoeff=%s, yCoeff=%s, confidence=%f",
|
|
int(outEstimator->degree),
|
|
vectorToString(outEstimator->xCoeff, n).string(),
|
|
vectorToString(outEstimator->yCoeff, n).string(),
|
|
outEstimator->confidence);
|
|
#endif
|
|
return true;
|
|
}
|
|
}
|
|
|
|
// No velocity data available for this pointer, but we do have its current position.
|
|
outEstimator->xCoeff[0] = x[0];
|
|
outEstimator->yCoeff[0] = y[0];
|
|
outEstimator->time = newestMovement.eventTime;
|
|
outEstimator->degree = 0;
|
|
outEstimator->confidence = 1;
|
|
return true;
|
|
}
|
|
|
|
float LeastSquaresVelocityTrackerStrategy::chooseWeight(uint32_t index) const {
|
|
switch (mWeighting) {
|
|
case WEIGHTING_DELTA: {
|
|
// Weight points based on how much time elapsed between them and the next
|
|
// point so that points that "cover" a shorter time span are weighed less.
|
|
// delta 0ms: 0.5
|
|
// delta 10ms: 1.0
|
|
if (index == mIndex) {
|
|
return 1.0f;
|
|
}
|
|
uint32_t nextIndex = (index + 1) % HISTORY_SIZE;
|
|
float deltaMillis = (mMovements[nextIndex].eventTime- mMovements[index].eventTime)
|
|
* 0.000001f;
|
|
if (deltaMillis < 0) {
|
|
return 0.5f;
|
|
}
|
|
if (deltaMillis < 10) {
|
|
return 0.5f + deltaMillis * 0.05;
|
|
}
|
|
return 1.0f;
|
|
}
|
|
|
|
case WEIGHTING_CENTRAL: {
|
|
// Weight points based on their age, weighing very recent and very old points less.
|
|
// age 0ms: 0.5
|
|
// age 10ms: 1.0
|
|
// age 50ms: 1.0
|
|
// age 60ms: 0.5
|
|
float ageMillis = (mMovements[mIndex].eventTime - mMovements[index].eventTime)
|
|
* 0.000001f;
|
|
if (ageMillis < 0) {
|
|
return 0.5f;
|
|
}
|
|
if (ageMillis < 10) {
|
|
return 0.5f + ageMillis * 0.05;
|
|
}
|
|
if (ageMillis < 50) {
|
|
return 1.0f;
|
|
}
|
|
if (ageMillis < 60) {
|
|
return 0.5f + (60 - ageMillis) * 0.05;
|
|
}
|
|
return 0.5f;
|
|
}
|
|
|
|
case WEIGHTING_RECENT: {
|
|
// Weight points based on their age, weighing older points less.
|
|
// age 0ms: 1.0
|
|
// age 50ms: 1.0
|
|
// age 100ms: 0.5
|
|
float ageMillis = (mMovements[mIndex].eventTime - mMovements[index].eventTime)
|
|
* 0.000001f;
|
|
if (ageMillis < 50) {
|
|
return 1.0f;
|
|
}
|
|
if (ageMillis < 100) {
|
|
return 0.5f + (100 - ageMillis) * 0.01f;
|
|
}
|
|
return 0.5f;
|
|
}
|
|
|
|
case WEIGHTING_NONE:
|
|
default:
|
|
return 1.0f;
|
|
}
|
|
}
|
|
|
|
|
|
// --- IntegratingVelocityTrackerStrategy ---
|
|
|
|
IntegratingVelocityTrackerStrategy::IntegratingVelocityTrackerStrategy(uint32_t degree) :
|
|
mDegree(degree) {
|
|
}
|
|
|
|
IntegratingVelocityTrackerStrategy::~IntegratingVelocityTrackerStrategy() {
|
|
}
|
|
|
|
void IntegratingVelocityTrackerStrategy::clear() {
|
|
mPointerIdBits.clear();
|
|
}
|
|
|
|
void IntegratingVelocityTrackerStrategy::clearPointers(BitSet32 idBits) {
|
|
mPointerIdBits.value &= ~idBits.value;
|
|
}
|
|
|
|
void IntegratingVelocityTrackerStrategy::addMovement(nsecs_t eventTime, BitSet32 idBits,
|
|
const VelocityTracker::Position* positions) {
|
|
uint32_t index = 0;
|
|
for (BitSet32 iterIdBits(idBits); !iterIdBits.isEmpty();) {
|
|
uint32_t id = iterIdBits.clearFirstMarkedBit();
|
|
State& state = mPointerState[id];
|
|
const VelocityTracker::Position& position = positions[index++];
|
|
if (mPointerIdBits.hasBit(id)) {
|
|
updateState(state, eventTime, position.x, position.y);
|
|
} else {
|
|
initState(state, eventTime, position.x, position.y);
|
|
}
|
|
}
|
|
|
|
mPointerIdBits = idBits;
|
|
}
|
|
|
|
bool IntegratingVelocityTrackerStrategy::getEstimator(uint32_t id,
|
|
VelocityTracker::Estimator* outEstimator) const {
|
|
outEstimator->clear();
|
|
|
|
if (mPointerIdBits.hasBit(id)) {
|
|
const State& state = mPointerState[id];
|
|
populateEstimator(state, outEstimator);
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
void IntegratingVelocityTrackerStrategy::initState(State& state,
|
|
nsecs_t eventTime, float xpos, float ypos) const {
|
|
state.updateTime = eventTime;
|
|
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) const {
|
|
const nsecs_t MIN_TIME_DELTA = 2 * NANOS_PER_MS;
|
|
const float FILTER_TIME_CONSTANT = 0.010f; // 10 milliseconds
|
|
|
|
if (eventTime <= state.updateTime + MIN_TIME_DELTA) {
|
|
return;
|
|
}
|
|
|
|
float dt = (eventTime - state.updateTime) * 0.000000001f;
|
|
state.updateTime = eventTime;
|
|
|
|
float xvel = (xpos - state.xpos) / dt;
|
|
float yvel = (ypos - state.ypos) / dt;
|
|
if (state.degree == 0) {
|
|
state.xvel = xvel;
|
|
state.yvel = yvel;
|
|
state.degree = 1;
|
|
} else {
|
|
float alpha = dt / (FILTER_TIME_CONSTANT + dt);
|
|
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) const {
|
|
outEstimator->time = state.updateTime;
|
|
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;
|
|
}
|
|
|
|
|
|
// --- LegacyVelocityTrackerStrategy ---
|
|
|
|
const nsecs_t LegacyVelocityTrackerStrategy::HORIZON;
|
|
const uint32_t LegacyVelocityTrackerStrategy::HISTORY_SIZE;
|
|
const nsecs_t LegacyVelocityTrackerStrategy::MIN_DURATION;
|
|
|
|
LegacyVelocityTrackerStrategy::LegacyVelocityTrackerStrategy() {
|
|
clear();
|
|
}
|
|
|
|
LegacyVelocityTrackerStrategy::~LegacyVelocityTrackerStrategy() {
|
|
}
|
|
|
|
void LegacyVelocityTrackerStrategy::clear() {
|
|
mIndex = 0;
|
|
mMovements[0].idBits.clear();
|
|
}
|
|
|
|
void LegacyVelocityTrackerStrategy::clearPointers(BitSet32 idBits) {
|
|
BitSet32 remainingIdBits(mMovements[mIndex].idBits.value & ~idBits.value);
|
|
mMovements[mIndex].idBits = remainingIdBits;
|
|
}
|
|
|
|
void LegacyVelocityTrackerStrategy::addMovement(nsecs_t eventTime, BitSet32 idBits,
|
|
const VelocityTracker::Position* positions) {
|
|
if (++mIndex == HISTORY_SIZE) {
|
|
mIndex = 0;
|
|
}
|
|
|
|
Movement& movement = mMovements[mIndex];
|
|
movement.eventTime = eventTime;
|
|
movement.idBits = idBits;
|
|
uint32_t count = idBits.count();
|
|
for (uint32_t i = 0; i < count; i++) {
|
|
movement.positions[i] = positions[i];
|
|
}
|
|
}
|
|
|
|
bool LegacyVelocityTrackerStrategy::getEstimator(uint32_t id,
|
|
VelocityTracker::Estimator* outEstimator) const {
|
|
outEstimator->clear();
|
|
|
|
const Movement& newestMovement = mMovements[mIndex];
|
|
if (!newestMovement.idBits.hasBit(id)) {
|
|
return false; // no data
|
|
}
|
|
|
|
// Find the oldest sample that contains the pointer and that is not older than HORIZON.
|
|
nsecs_t minTime = newestMovement.eventTime - HORIZON;
|
|
uint32_t oldestIndex = mIndex;
|
|
uint32_t numTouches = 1;
|
|
do {
|
|
uint32_t nextOldestIndex = (oldestIndex == 0 ? HISTORY_SIZE : oldestIndex) - 1;
|
|
const Movement& nextOldestMovement = mMovements[nextOldestIndex];
|
|
if (!nextOldestMovement.idBits.hasBit(id)
|
|
|| nextOldestMovement.eventTime < minTime) {
|
|
break;
|
|
}
|
|
oldestIndex = nextOldestIndex;
|
|
} while (++numTouches < HISTORY_SIZE);
|
|
|
|
// Calculate an exponentially weighted moving average of the velocity estimate
|
|
// at different points in time measured relative to the oldest sample.
|
|
// This is essentially an IIR filter. Newer samples are weighted more heavily
|
|
// than older samples. Samples at equal time points are weighted more or less
|
|
// equally.
|
|
//
|
|
// One tricky problem is that the sample data may be poorly conditioned.
|
|
// Sometimes samples arrive very close together in time which can cause us to
|
|
// overestimate the velocity at that time point. Most samples might be measured
|
|
// 16ms apart but some consecutive samples could be only 0.5sm apart because
|
|
// the hardware or driver reports them irregularly or in bursts.
|
|
float accumVx = 0;
|
|
float accumVy = 0;
|
|
uint32_t index = oldestIndex;
|
|
uint32_t samplesUsed = 0;
|
|
const Movement& oldestMovement = mMovements[oldestIndex];
|
|
const VelocityTracker::Position& oldestPosition = oldestMovement.getPosition(id);
|
|
nsecs_t lastDuration = 0;
|
|
|
|
while (numTouches-- > 1) {
|
|
if (++index == HISTORY_SIZE) {
|
|
index = 0;
|
|
}
|
|
const Movement& movement = mMovements[index];
|
|
nsecs_t duration = movement.eventTime - oldestMovement.eventTime;
|
|
|
|
// If the duration between samples is small, we may significantly overestimate
|
|
// the velocity. Consequently, we impose a minimum duration constraint on the
|
|
// samples that we include in the calculation.
|
|
if (duration >= MIN_DURATION) {
|
|
const VelocityTracker::Position& position = movement.getPosition(id);
|
|
float scale = 1000000000.0f / duration; // one over time delta in seconds
|
|
float vx = (position.x - oldestPosition.x) * scale;
|
|
float vy = (position.y - oldestPosition.y) * scale;
|
|
accumVx = (accumVx * lastDuration + vx * duration) / (duration + lastDuration);
|
|
accumVy = (accumVy * lastDuration + vy * duration) / (duration + lastDuration);
|
|
lastDuration = duration;
|
|
samplesUsed += 1;
|
|
}
|
|
}
|
|
|
|
// Report velocity.
|
|
const VelocityTracker::Position& newestPosition = newestMovement.getPosition(id);
|
|
outEstimator->time = newestMovement.eventTime;
|
|
outEstimator->confidence = 1;
|
|
outEstimator->xCoeff[0] = newestPosition.x;
|
|
outEstimator->yCoeff[0] = newestPosition.y;
|
|
if (samplesUsed) {
|
|
outEstimator->xCoeff[1] = accumVx;
|
|
outEstimator->yCoeff[1] = accumVy;
|
|
outEstimator->degree = 1;
|
|
} else {
|
|
outEstimator->degree = 0;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
} // namespace android
|