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base the tides on the viewer, moon and sun longitude for an accurate prediction.

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This commit is contained in:
Erik Hofman 2020-10-22 20:44:42 +02:00
parent 3e75668194
commit 029ad744b2
2 changed files with 19 additions and 16 deletions
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30
src/Time/tide.cxx
View file

@ -29,21 +29,23 @@
#include "bodysolver.hxx"
void FGTide::reinit() {
_prev_moon_rotation = -9999.0;
_prev_moon_lon = -9999.0;
}
void FGTide::bind()
{
SGPropertyNode *prop = globals->get_props();
SGPropertyNode *props = globals->get_props();
_tideAnimation = prop->getNode("/environment/sea/surface/delta-T-tide", true);
viewLon = props->getNode("sim/current-view/viewer-lon-deg", true);
_tideAnimation = props->getNode("/environment/sea/surface/delta-T-tide", true);
_tideLevelNorm = prop->getNode("/sim/time/tide-level-norm", true);
_tideLevelNorm = props->getNode("/sim/time/tide-level-norm", true);
_tideLevelNorm->setDoubleValue(_tide_level);
}
void FGTide::unbind()
{
viewLon.reset();
_tideLevelNorm.reset();
_tideAnimation.reset();
}
@ -51,19 +53,21 @@ void FGTide::unbind()
void FGTide::update(double dt)
{
FGLight *l = static_cast<FGLight*>(globals->get_subsystem("lighting"));
double moon_rotation = l->get_moon_rotation();
if (fabs(_prev_moon_rotation - moon_rotation) > (SGD_PI/180.0))
double moon_lon = l->get_moon_lon();
if (fabs(_prev_moon_lon - moon_lon) > (SGD_PI/180.0))
{
// double sun_rotation = _sunAngleRad->getDoubleValue();
_prev_moon_rotation = moon_rotation;
_prev_moon_lon = moon_lon;
// Angles range from 0.0 (straight up) to pi (straight down).
// The sun and moon rotate once every day (approximately) but tides
// happen twice a day.
_tide_level = cos(2.0*moon_rotation);
double sun_lon = l->get_sun_lon();
double viewer_lon = viewLon->getDoubleValue();
_tide_level = cos(2.0*(moon_lon - viewer_lon));
_tide_level += 0.1*cos(2.0*(sun_lon - viewer_lon));
if (_tide_level < -1.0) _tide_level = -1.0;
else if (_tide_level > 1.0) _tide_level = 1.0;
_tideLevelNorm->setDoubleValue(_tide_level);
_tideAnimation->setDoubleValue(0.5 + 0.5*_tide_level);
_tideAnimation->setDoubleValue(0.5 - 0.5*_tide_level);
}
}

5
src/Time/tide.hxx
View file

@ -50,11 +50,10 @@ public:
static const char* staticSubsystemClassId() { return "tides"; }
private:
// the rotation between the celestial object and the local horizontal
// (in radians)
double _prev_moon_rotation = -9999.0;
double _prev_moon_lon = -9999.0;
double _tide_level = 0;
SGPropertyNode_ptr viewLon;
SGPropertyNode_ptr _tideLevelNorm;
SGPropertyNode_ptr _tideAnimation;
};