linear_interpolation.h

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/******************************************************************************
 * Copyright 2017 The Apollo Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *****************************************************************************/

#pragma once

#include <cmath>

#include "cyber/common/log.h"
#include "modules/common/proto/pnc_point.pb.h"

namespace apollo {
namespace common {
namespace math {

template <typename T>
T lerp(const T &x0, const double t0, const T &x1, const double t1,
       const double t) {
  if (std::abs(t1 - t0) <= 1.0e-6) {
    AERROR << "input time difference is too small";
    return x0;
  }
  const double r = (t - t0) / (t1 - t0);
  const T x = x0 + r * (x1 - x0);
  return x;
}

double slerp(const double a0, const double t0, const double a1, const double t1,
             const double t);

SLPoint InterpolateUsingLinearApproximation(const SLPoint &p0,
                                            const SLPoint &p1, const double w);

PathPoint InterpolateUsingLinearApproximation(const PathPoint &p0,
                                              const PathPoint &p1,
                                              const double s);

TrajectoryPoint InterpolateUsingLinearApproximation(const TrajectoryPoint &tp0,
                                                    const TrajectoryPoint &tp1,
                                                    const double t);

}  // namespace math
}  // namespace common
}  // namespace apollo