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Diffstat (limited to 'game/environment.cpp')
| -rw-r--r-- | game/environment.cpp | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/game/environment.cpp b/game/environment.cpp new file mode 100644 index 0000000..19aad84 --- /dev/null +++ b/game/environment.cpp @@ -0,0 +1,94 @@ +#include "environment.h" +#include <chronology.h> +#include <gfx/gl/sceneRenderer.h> + +Environment::Environment() : worldTime {"2024-01-01T12:00:00"_time_t} { } + +void +Environment::tick(TickDuration) +{ + worldTime += 50; +} + +void +Environment::render(const SceneRenderer & renderer, const SceneProvider & scene) const +{ + constexpr RGB baseAmbient {0.1F}, baseDirectional {0.0F}; + constexpr RGB relativeAmbient {0.3F, 0.3F, 0.4F}, relativeDirectional {0.6F, 0.6F, 0.5F}; + + const auto sunPos = getSunPos({}, worldTime); + const auto sunDir = (glm::mat3 {rotate_yp({sunPos.y + pi, sunPos.x})} * north); + const auto vertical = -std::min(0.F, sunDir.z - 0.1F); + const auto ambient = baseAmbient + relativeAmbient * vertical; + const auto directional = baseDirectional + relativeDirectional * vertical; + + renderer.setAmbientLight(ambient); + renderer.setDirectionalLight(directional, sunDir, scene); +} + +// Based on the C++ code published at https://www.psa.es/sdg/sunpos.htm +// Linked from https://www.pveducation.org/pvcdrom/properties-of-sunlight/suns-position-to-high-accuracy +Direction2D +Environment::getSunPos(const Direction2D position, const time_t time) +{ + auto & longitude = position.x; + auto & latitude = position.y; + using std::acos; + using std::asin; + using std::atan2; + using std::cos; + using std::floor; + using std::sin; + using std::tan; + static const auto JD2451545 = "2000-01-01T12:00:00"_time_t; + + // Calculate difference in days between the current Julian Day + // and JD 2451545.0, which is noon 1 January 2000 Universal Time + // Calculate time of the day in UT decimal hours + const auto dDecimalHours = static_cast<float>(time % 86400) / 3600.F; + const auto dElapsedJulianDays = static_cast<float>(time - JD2451545) / 86400.F; + + // Calculate ecliptic coordinates (ecliptic longitude and obliquity of the + // ecliptic in radians but without limiting the angle to be less than 2*Pi + // (i.e., the result may be greater than 2*Pi) + const auto dOmega = 2.1429F - 0.0010394594F * dElapsedJulianDays; + const auto dMeanLongitude = 4.8950630F + 0.017202791698F * dElapsedJulianDays; // Radians + const auto dMeanAnomaly = 6.2400600F + 0.0172019699F * dElapsedJulianDays; + const auto dEclipticLongitude = dMeanLongitude + 0.03341607F * sin(dMeanAnomaly) + + 0.00034894F * sin(2 * dMeanAnomaly) - 0.0001134F - 0.0000203F * sin(dOmega); + const auto dEclipticObliquity = 0.4090928F - 6.2140e-9F * dElapsedJulianDays + 0.0000396F * cos(dOmega); + + // Calculate celestial coordinates ( right ascension and declination ) in radians + // but without limiting the angle to be less than 2*Pi (i.e., the result may be + // greater than 2*Pi) + const auto dSin_EclipticLongitude = sin(dEclipticLongitude); + const auto dY = cos(dEclipticObliquity) * dSin_EclipticLongitude; + const auto dX = cos(dEclipticLongitude); + auto dRightAscension = atan2(dY, dX); + if (dRightAscension < 0) { + dRightAscension = dRightAscension + two_pi; + } + const auto dDeclination = asin(sin(dEclipticObliquity) * dSin_EclipticLongitude); + + // Calculate local coordinates ( azimuth and zenith angle ) in degrees + const auto dGreenwichMeanSiderealTime = 6.6974243242F + 0.0657098283F * dElapsedJulianDays + dDecimalHours; + const auto dLocalMeanSiderealTime + = (dGreenwichMeanSiderealTime * 15.0F + (longitude / degreesToRads)) * degreesToRads; + const auto dHourAngle = dLocalMeanSiderealTime - dRightAscension; + const auto dLatitudeInRadians = latitude; + const auto dCos_Latitude = cos(dLatitudeInRadians); + const auto dSin_Latitude = sin(dLatitudeInRadians); + const auto dCos_HourAngle = cos(dHourAngle); + Direction2D udtSunCoordinates; + udtSunCoordinates.y + = (acos(dCos_Latitude * dCos_HourAngle * cos(dDeclination) + sin(dDeclination) * dSin_Latitude)); + udtSunCoordinates.x = atan2(-sin(dHourAngle), tan(dDeclination) * dCos_Latitude - dSin_Latitude * dCos_HourAngle); + if (udtSunCoordinates.x < 0) { + udtSunCoordinates.x = udtSunCoordinates.x + two_pi; + } + // Parallax Correction + const auto dParallax = (earthMeanRadius / astronomicalUnit) * sin(udtSunCoordinates.y); + udtSunCoordinates.y = half_pi - (udtSunCoordinates.y + dParallax); + + return udtSunCoordinates; +} |