blackbody.hpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code 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, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper source code 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef ANTKEEPER_PHYSICS_LIGHT_BLACKBODY_HPP
#define ANTKEEPER_PHYSICS_LIGHT_BLACKBODY_HPP
 
#include <engine/math/numbers.hpp>
#include <engine/physics/constants.hpp>
 
namespace physics {
namespace light {
 
namespace blackbody {
 
template <class T>
T radiant_exitance(T t);
 
template <class T>
T radiant_flux(T t, T a);
 
template <class T>
T radiant_intensity(T t, T a, T omega);
 
template <class T>
T spectral_flux(T t, T a, T lambda, T c = constants::speed_of_light<T>);
 
template <class T>
T spectral_intensity(T t, T a, T lambda, T omega, T c = constants::speed_of_light<T>);
 
template <class T>
T spectral_radiance(T t, T lambda, T c = constants::speed_of_light<T>);
 
template <class T>
T radiant_exitance(T t)
{
    const T tt = t * t;
    return constants::stefan_boltzmann<T> * (tt * tt);
}
 
template <class T>
T radiant_flux(T t, T a)
{
    return a * radiant_exitance(t);
}
 
template <class T>
T radiant_intensity(T t, T a, T omega)
{
    return radiant_flux(t, a) / omega;
}
 
template <class T>
T spectral_exitance(T t, T lambda, T c)
{
    const T hc = constants::planck<T> * c;
    const T lambda2 = lambda * lambda;
    
    // First radiation constant (c1)
    const T c1 = math::two_pi<T> * hc * c;
    
    // Second radiation constant (c2)
    const T c2 = hc / constants::boltzmann<T>;
    
    return (c1 / (lambda2 * lambda2 * lambda)) / std::expm1(c2 / (lambda * t));
}
 
template <class T>
T spectral_flux(T t, T a, T lambda, T c)
{
    return a * spectral_exitance(t, lambda, c);
}
 
template <class T>
T spectral_intensity(T t, T a, T lambda, T omega, T c)
{
    return spectral_flux(t, a, lambda, c) / omega;
}
 
template <class T>
T spectral_radiance(T t, T lambda, T c)
{
    const T hc = constants::planck<T> * c;
    const T lambda2 = lambda * lambda;
    
    // First radiation constant (c1L)
    const T c1l = T{2} * hc * c;
    
    // Second radiation constant (c2)
    const T c2 = hc / constants::boltzmann<T>;
    
    return (c1l / (lambda2 * lambda2 * lambda)) / std::expm1(c2 / (lambda * t));
}
 
} // namespace blackbody
 
} // namespace light
} // namespace physics
 
#endif // ANTKEEPER_PHYSICS_LIGHT_BLACKBODY_HPP