This file defines the size of the precomputed texures used in our atmosphere model. It also provides tabulated values of the CIE color matching functions and the conversion matrix from the XYZ to the sRGB color spaces (which are needed to convert the spectral radiance samples computed by our algorithm to sRGB luminance values).
#ifndef ATMOSPHERE_CONSTANTS_H_
#define ATMOSPHERE_CONSTANTS_H_
namespace atmosphere {
constexpr int TRANSMITTANCE_TEXTURE_WIDTH = 256;
constexpr int TRANSMITTANCE_TEXTURE_HEIGHT = 64;
constexpr int SCATTERING_TEXTURE_R_SIZE = 32;
constexpr int SCATTERING_TEXTURE_MU_SIZE = 128;
constexpr int SCATTERING_TEXTURE_MU_S_SIZE = 32;
constexpr int SCATTERING_TEXTURE_NU_SIZE = 8;
constexpr int SCATTERING_TEXTURE_WIDTH =
SCATTERING_TEXTURE_NU_SIZE * SCATTERING_TEXTURE_MU_S_SIZE;
constexpr int SCATTERING_TEXTURE_HEIGHT = SCATTERING_TEXTURE_MU_SIZE;
constexpr int SCATTERING_TEXTURE_DEPTH = SCATTERING_TEXTURE_R_SIZE;
constexpr int IRRADIANCE_TEXTURE_WIDTH = 64;
constexpr int IRRADIANCE_TEXTURE_HEIGHT = 16;
// The conversion factor between watts and lumens.
constexpr double MAX_LUMINOUS_EFFICACY = 683.0;
// Values from "CIE (1931) 2-deg color matching functions", see
// "http://web.archive.org/web/20081228084047/
// http://www.cvrl.org/database/data/cmfs/ciexyz31.txt".
constexpr double CIE_2_DEG_COLOR_MATCHING_FUNCTIONS[380] = {
360, 0.000129900000, 0.000003917000, 0.000606100000,
365, 0.000232100000, 0.000006965000, 0.001086000000,
370, 0.000414900000, 0.000012390000, 0.001946000000,
375, 0.000741600000, 0.000022020000, 0.003486000000,
380, 0.001368000000, 0.000039000000, 0.006450001000,
385, 0.002236000000, 0.000064000000, 0.010549990000,
390, 0.004243000000, 0.000120000000, 0.020050010000,
395, 0.007650000000, 0.000217000000, 0.036210000000,
400, 0.014310000000, 0.000396000000, 0.067850010000,
405, 0.023190000000, 0.000640000000, 0.110200000000,
410, 0.043510000000, 0.001210000000, 0.207400000000,
415, 0.077630000000, 0.002180000000, 0.371300000000,
420, 0.134380000000, 0.004000000000, 0.645600000000,
425, 0.214770000000, 0.007300000000, 1.039050100000,
430, 0.283900000000, 0.011600000000, 1.385600000000,
435, 0.328500000000, 0.016840000000, 1.622960000000,
440, 0.348280000000, 0.023000000000, 1.747060000000,
445, 0.348060000000, 0.029800000000, 1.782600000000,
450, 0.336200000000, 0.038000000000, 1.772110000000,
455, 0.318700000000, 0.048000000000, 1.744100000000,
460, 0.290800000000, 0.060000000000, 1.669200000000,
465, 0.251100000000, 0.073900000000, 1.528100000000,
470, 0.195360000000, 0.090980000000, 1.287640000000,
475, 0.142100000000, 0.112600000000, 1.041900000000,
480, 0.095640000000, 0.139020000000, 0.812950100000,
485, 0.057950010000, 0.169300000000, 0.616200000000,
490, 0.032010000000, 0.208020000000, 0.465180000000,
495, 0.014700000000, 0.258600000000, 0.353300000000,
500, 0.004900000000, 0.323000000000, 0.272000000000,
505, 0.002400000000, 0.407300000000, 0.212300000000,
510, 0.009300000000, 0.503000000000, 0.158200000000,
515, 0.029100000000, 0.608200000000, 0.111700000000,
520, 0.063270000000, 0.710000000000, 0.078249990000,
525, 0.109600000000, 0.793200000000, 0.057250010000,
530, 0.165500000000, 0.862000000000, 0.042160000000,
535, 0.225749900000, 0.914850100000, 0.029840000000,
540, 0.290400000000, 0.954000000000, 0.020300000000,
545, 0.359700000000, 0.980300000000, 0.013400000000,
550, 0.433449900000, 0.994950100000, 0.008749999000,
555, 0.512050100000, 1.000000000000, 0.005749999000,
560, 0.594500000000, 0.995000000000, 0.003900000000,
565, 0.678400000000, 0.978600000000, 0.002749999000,
570, 0.762100000000, 0.952000000000, 0.002100000000,
575, 0.842500000000, 0.915400000000, 0.001800000000,
580, 0.916300000000, 0.870000000000, 0.001650001000,
585, 0.978600000000, 0.816300000000, 0.001400000000,
590, 1.026300000000, 0.757000000000, 0.001100000000,
595, 1.056700000000, 0.694900000000, 0.001000000000,
600, 1.062200000000, 0.631000000000, 0.000800000000,
605, 1.045600000000, 0.566800000000, 0.000600000000,
610, 1.002600000000, 0.503000000000, 0.000340000000,
615, 0.938400000000, 0.441200000000, 0.000240000000,
620, 0.854449900000, 0.381000000000, 0.000190000000,
625, 0.751400000000, 0.321000000000, 0.000100000000,
630, 0.642400000000, 0.265000000000, 0.000049999990,
635, 0.541900000000, 0.217000000000, 0.000030000000,
640, 0.447900000000, 0.175000000000, 0.000020000000,
645, 0.360800000000, 0.138200000000, 0.000010000000,
650, 0.283500000000, 0.107000000000, 0.000000000000,
655, 0.218700000000, 0.081600000000, 0.000000000000,
660, 0.164900000000, 0.061000000000, 0.000000000000,
665, 0.121200000000, 0.044580000000, 0.000000000000,
670, 0.087400000000, 0.032000000000, 0.000000000000,
675, 0.063600000000, 0.023200000000, 0.000000000000,
680, 0.046770000000, 0.017000000000, 0.000000000000,
685, 0.032900000000, 0.011920000000, 0.000000000000,
690, 0.022700000000, 0.008210000000, 0.000000000000,
695, 0.015840000000, 0.005723000000, 0.000000000000,
700, 0.011359160000, 0.004102000000, 0.000000000000,
705, 0.008110916000, 0.002929000000, 0.000000000000,
710, 0.005790346000, 0.002091000000, 0.000000000000,
715, 0.004109457000, 0.001484000000, 0.000000000000,
720, 0.002899327000, 0.001047000000, 0.000000000000,
725, 0.002049190000, 0.000740000000, 0.000000000000,
730, 0.001439971000, 0.000520000000, 0.000000000000,
735, 0.000999949300, 0.000361100000, 0.000000000000,
740, 0.000690078600, 0.000249200000, 0.000000000000,
745, 0.000476021300, 0.000171900000, 0.000000000000,
750, 0.000332301100, 0.000120000000, 0.000000000000,
755, 0.000234826100, 0.000084800000, 0.000000000000,
760, 0.000166150500, 0.000060000000, 0.000000000000,
765, 0.000117413000, 0.000042400000, 0.000000000000,
770, 0.000083075270, 0.000030000000, 0.000000000000,
775, 0.000058706520, 0.000021200000, 0.000000000000,
780, 0.000041509940, 0.000014990000, 0.000000000000,
785, 0.000029353260, 0.000010600000, 0.000000000000,
790, 0.000020673830, 0.000007465700, 0.000000000000,
795, 0.000014559770, 0.000005257800, 0.000000000000,
800, 0.000010253980, 0.000003702900, 0.000000000000,
805, 0.000007221456, 0.000002607800, 0.000000000000,
810, 0.000005085868, 0.000001836600, 0.000000000000,
815, 0.000003581652, 0.000001293400, 0.000000000000,
820, 0.000002522525, 0.000000910930, 0.000000000000,
825, 0.000001776509, 0.000000641530, 0.000000000000,
830, 0.000001251141, 0.000000451810, 0.000000000000,
};
// The conversion matrix from XYZ to linear sRGB color spaces.
// Values from https://en.wikipedia.org/wiki/SRGB.
constexpr double XYZ_TO_SRGB[9] = {
+3.2406, -1.5372, -0.4986,
-0.9689, +1.8758, +0.0415,
+0.0557, -0.2040, +1.0570
};
} // namespace atmosphere
#endif // ATMOSPHERE_CONSTANTS_H_