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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "ui/base/prediction/kalman_predictor.h"
#include <algorithm>
#include <cmath>
#include "base/numerics/angle_conversions.h"
#include "base/time/time.h"
#include "ui/base/ui_base_features.h"
namespace {
// Influence of acceleration during each prediction sample
constexpr float kAccelerationInfluence = 0.5f;
// Influence of velocity during each prediction sample
constexpr float kVelocityInfluence = 1.0f;
} // namespace
namespace ui {
constexpr base::TimeDelta InputPredictor::kMaxTimeDelta;
constexpr base::TimeDelta InputPredictor::kMaxResampleTime;
constexpr base::TimeDelta InputPredictor::kMaxPredictionTime;
constexpr base::TimeDelta InputPredictor::kTimeInterval;
constexpr base::TimeDelta InputPredictor::kMinTimeInterval;
constexpr base::TimeDelta KalmanPredictor::kMaxTimeInQueue;
KalmanPredictor::KalmanPredictor(unsigned int prediction_options)
: prediction_options_(prediction_options) {}
KalmanPredictor::~KalmanPredictor() = default;
const char* KalmanPredictor::GetName() const {
return features::kPredictorNameKalman;
}
void KalmanPredictor::Reset() {
x_predictor_.Reset();
y_predictor_.Reset();
last_points_.clear();
time_filter_.Reset();
}
void KalmanPredictor::Update(const InputData& cur_input) {
base::TimeDelta dt;
if (last_points_.size()) {
// When last point is kMaxTimeDelta away, consider it is incontinuous.
dt = cur_input.time_stamp - last_points_.back().time_stamp;
if (dt > kMaxTimeDelta)
Reset();
else
time_filter_.Update(dt.InMillisecondsF(), 0);
}
double dt_ms = time_filter_.GetPosition();
last_points_.push_back(cur_input);
x_predictor_.Update(cur_input.pos.x(), dt_ms);
y_predictor_.Update(cur_input.pos.y(), dt_ms);
while (last_points_.back().time_stamp - last_points_.front().time_stamp >
kMaxTimeInQueue) {
last_points_.pop_front();
}
}
bool KalmanPredictor::HasPrediction() const {
return x_predictor_.Stable() && y_predictor_.Stable();
}
std::unique_ptr<InputPredictor::InputData> KalmanPredictor::GeneratePrediction(
base::TimeTicks predict_time,
base::TimeDelta frame_interval) {
if (!HasPrediction())
return nullptr;
DCHECK(last_points_.size());
float pred_dt =
(predict_time - last_points_.back().time_stamp).InMillisecondsF();
gfx::PointF position(last_points_.back().pos.x(),
last_points_.back().pos.y());
gfx::Vector2dF velocity = PredictVelocity();
gfx::Vector2dF acceleration = PredictAcceleration();
if (prediction_options_ & kDirectionCutOffEnabled) {
gfx::Vector2dF future_velocity =
velocity + ScaleVector2d(acceleration, pred_dt);
if (gfx::DotProduct(velocity, future_velocity) <= 0)
return nullptr;
}
position += ScaleVector2d(velocity, kVelocityInfluence * pred_dt);
if (prediction_options_ & kHeuristicsEnabled) {
float points_angle = 0.0f;
for (size_t i = 2; i < last_points_.size(); i++) {
gfx::Vector2dF first_dir =
last_points_[i - 1].pos - last_points_[i - 2].pos;
gfx::Vector2dF second_dir = last_points_[i].pos - last_points_[i - 1].pos;
if (first_dir.Length() && second_dir.Length()) {
points_angle += atan2(first_dir.x(), first_dir.y()) -
atan2(second_dir.x(), second_dir.y());
}
}
if (base::RadToDeg(fabsf(points_angle)) > 15) {
position += ScaleVector2d(acceleration,
kAccelerationInfluence * pred_dt * pred_dt);
}
} else {
position +=
ScaleVector2d(acceleration, kAccelerationInfluence * pred_dt * pred_dt);
}
return std::make_unique<InputData>(position, predict_time);
}
base::TimeDelta KalmanPredictor::TimeInterval() const {
return time_filter_.GetPosition()
? std::max(kMinTimeInterval,
base::Milliseconds(time_filter_.GetPosition()))
: kTimeInterval;
}
gfx::Vector2dF KalmanPredictor::PredictPosition() const {
return gfx::Vector2dF(x_predictor_.GetPosition(), y_predictor_.GetPosition());
}
gfx::Vector2dF KalmanPredictor::PredictVelocity() const {
return gfx::Vector2dF(x_predictor_.GetVelocity(), y_predictor_.GetVelocity());
}
gfx::Vector2dF KalmanPredictor::PredictAcceleration() const {
return gfx::Vector2dF(x_predictor_.GetAcceleration(),
y_predictor_.GetAcceleration());
}
} // namespace ui
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