|
|
- /*
- * Copyright (C) 2021 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_LUMINOSITY_HPP
- #define ANTKEEPER_PHYSICS_LIGHT_LUMINOSITY_HPP
-
- #include <cmath>
-
- namespace physics {
- namespace light {
-
- /// Luminous efficiency functions.
- namespace luminosity {
-
- /**
- * Fitted Gaussian approximation to the CIE 1931 standard observer photopic luminosity function.
- *
- * @param lambda Wavelength of light, in nanometers.
- * @return Luminous efficiency, on `[0, 1]`.
- *
- * @see Wyman, C., Sloan, P.J., & Shirley, P. (2013). Simple Analytic Approximations to the CIE XYZ Color Matching Functions.
- */
- template <class T>
- T photopic(T lambda)
- {
- const T t0 = (lambda - T(568.8)) * ((lambda < T(568.8)) ? T(0.0213) : T(0.0247));
- const T t1 = (lambda - T(530.9)) * ((lambda < T(530.9)) ? T(0.0613) : T(0.0322));
-
- const T y0 = T(0.821) * std::exp(T(-0.5) * t0 * t0);
- const T y1 = T(0.286) * std::exp(T(-0.5) * t1 * t1);
-
- return y0 + y1;
- }
-
- } // namespace luminosity
-
- } // namespace light
- } // namespace physics
-
- #endif // ANTKEEPER_PHYSICS_LIGHT_LUMINOSITY_HPP
|