interpolation.hpp

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/* 
 * This file is part of PLaSK (https://plask.app) by Photonics Group at TUL
 * Copyright (c) 2022 Lodz University of Technology
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 */
#ifndef PLASK__UTILS_INTERPOLATION_H
#define PLASK__UTILS_INTERPOLATION_H
 
namespace plask { namespace interpolation {
 
    template <typename T>
    inline T linear(double p_lo, const T& d_lo, double p_hi, const T& d_hi, double p) {
        //return ((p_hi - p) * d_lo + (p - p_lo) * d_hi) / (p_hi - p_lo);
        return d_lo + (p - p_lo) / (p_hi - p_lo) * (d_hi - d_lo);
    }
 
    template <typename T>
    inline T bilinear(double p_l, double p_r, double p_b, double p_t,
                      const T& d_lb, const T& d_rb, const T& d_rt, const T& d_lt,
                      double p_x, double p_y) {
        const double delta_x_hi = p_r - p_x;
        const double delta_x_lo = p_x - p_l;
        return ((d_lb * delta_x_hi + d_rb * delta_x_lo) * (p_t - p_y) +
                (d_lt * delta_x_hi + d_rt * delta_x_lo) * (p_y - p_b))
                / (p_t - p_b) / (p_r - p_l);
    }
 
    template <typename T>
    inline T trilinear(double p_l, double p_r, double p_b, double p_t, double p_lo, double p_hi,
                      const T& lo_d_lb, const T& lo_d_rb, const T& lo_d_rt, const T& lo_d_lt,
                      const T& hi_d_lb, const T& hi_d_rb, const T& hi_d_rt, const T& hi_d_lt,
                      double p_x, double p_y, double p_lohi) {
        return linear(p_lo, bilinear(p_l, p_r, p_b, p_t, lo_d_lb, lo_d_rb, lo_d_rt, lo_d_lt, p_x, p_y),
                      p_hi, bilinear(p_l, p_r, p_b, p_t, hi_d_lb, hi_d_rb, hi_d_rt, hi_d_lt, p_x, p_y),
                      p_lohi);
    }
 
} }
 
#endif // PLASK__UTILS_INTERPOLATION_H