💿🐜 Antkeeper source code
https://antkeeper.com
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56 lines
1.7 KiB
56 lines
1.7 KiB
/*
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* Copyright (C) 2021 Christopher J. Howard
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*
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* This file is part of Antkeeper source code.
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*
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* Antkeeper source code is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Antkeeper source code is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef ANTKEEPER_PHYSICS_LIGHT_LUMINOSITY_HPP
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#define ANTKEEPER_PHYSICS_LIGHT_LUMINOSITY_HPP
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#include <cmath>
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namespace physics {
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namespace light {
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/// Luminous efficiency functions.
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namespace luminosity {
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/**
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* Fitted Gaussian approximation to the CIE 1931 standard observer photopic luminosity function.
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*
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* @param lambda Wavelength of light, in nanometers.
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* @return Luminous efficiency, on `[0, 1]`.
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*
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* @see Wyman, C., Sloan, P.J., & Shirley, P. (2013). Simple Analytic Approximations to the CIE XYZ Color Matching Functions.
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*/
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template <class T>
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T photopic(T lambda)
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{
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const T t0 = (lambda - T(568.8)) * ((lambda < T(568.8)) ? T(0.0213) : T(0.0247));
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const T t1 = (lambda - T(530.9)) * ((lambda < T(530.9)) ? T(0.0613) : T(0.0322));
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const T y0 = T(0.821) * std::exp(T(-0.5) * t0 * t0);
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const T y1 = T(0.286) * std::exp(T(-0.5) * t1 * t1);
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return y0 + y1;
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}
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} // namespace luminosity
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} // namespace light
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} // namespace physics
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#endif // ANTKEEPER_PHYSICS_LIGHT_LUMINOSITY_HPP
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