Move tide calculations from FGLight into it's own subsystem

src/Main/fg_init.cxx

@@ -115,6 +115,7 @@
 #include <Sound/voice.hxx>
 #include <Sound/soundmanager.hxx>
 #include <Systems/system_mgr.hxx>
+#include <Time/tide.hxx>
 #include <Time/light.hxx>
 #include <Time/TimeManager.hxx>
 
@@ -1117,6 +1118,7 @@ void fgCreateSubsystems(bool duringReset) {
     if (!duringReset) {
         globals->add_subsystem("lighting", new FGLight, SGSubsystemMgr::DISPLAY);
         globals->add_subsystem("events", globals->get_event_mgr(), SGSubsystemMgr::DISPLAY);
+        globals->add_subsystem("tides", new FGTide );
     }
 
     globals->add_new_subsystem<FGAircraftModel>(SGSubsystemMgr::DISPLAY);

src/Main/subsystemFactory.cxx

@@ -114,6 +114,7 @@ SGSubsystem* createSubsystemByName(const std::string& name)
 #ifdef ENABLE_SWIFT
     MAKE_SUB(SwiftConnection, "swift");
 #endif
+    MAKE_SUB(FGLight, "tides");
     MAKE_SUB(FGLight, "lighting");
     MAKE_SUB(FGAircraftModel, "aircraft-model");
     MAKE_SUB(FGModelMgr, "model-manager");

src/Time/CMakeLists.txt

@@ -3,12 +3,14 @@ include(FlightGearComponent)
 set(SOURCES
 	TimeManager.cxx
 	light.cxx
+        tide.cxx
 	bodysolver.cxx
 	)
 	
 set(HEADERS
 	TimeManager.hxx
 	light.hxx
+        tide.hxx
 	bodysolver.hxx
 	)
     	

src/Time/light.cxx

@@ -108,8 +108,6 @@ void FGLight::bind () {
     _sunAngleRad->setDoubleValue(_sun_angle);
     _moonAngleRad = prop->getNode("/sim/time/moon-angle-rad", true);
     _moonAngleRad->setDoubleValue(_moon_angle);
-    _tideLevelNorm = prop->getNode("/sim/time/tide-level-norm", true);
-    _tideLevelNorm->setDoubleValue(_tide_level_norm);
     _humidity = fgGetNode("/environment/relative-humidity", true);
 
     // Read Only
@@ -362,9 +360,6 @@ void FGLight::updateObjects()
     // update the moon position
     updateBodyPos("moon", &_moon_lon, &_moon_gc_lat, &_moon_vec, &_moon_vec_inv,
                   &_moon_angle, _moonAngleRad, &_moon_rotation);
-
-    _tide_level_norm = _moon_angle/SGD_PI;
-    _tideLevelNorm->setDoubleValue(_tide_level_norm);
 }
 
 // update the position of one solar system body

src/Time/light.hxx

@@ -73,7 +73,6 @@ private:
     // (in radians)
     double _sun_angle = 0.0 , _moon_angle = 0.0;
     double _prev_sun_angle = 0.0;
-    double _tide_level_norm = 0;
 
     // the rotation around our vertical axis of the sun (relative to
     // due south with positive numbers going in the counter clockwise
@@ -108,6 +107,7 @@ private:
 
     double _dt_total = 0.0;
 
+    void update_tide();
     void update_sky_color ();
     void update_adj_fog_color ();
 

src/Time/tide.cxx

@@ -0,0 +1,71 @@
+// tide.cxx -- interface for tidal movement
+//
+// Written by Erik Hofman, Octover 2020
+//
+// Copyright (C) 2020  Erik Hofman <erik@ehofman.com>
+//
+// This program 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 2 of the
+// License, or (at your option) any later version.
+//
+// This program 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 this program; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+//
+
+#include <simgear/constants.h>
+#include <simgear/timing/sg_time.hxx>
+#include <simgear/structure/SGExpression.hxx>
+#include <Main/globals.hxx>
+
+#include "tide.hxx"
+#include "light.hxx"
+#include "bodysolver.hxx"
+
+void FGTide::reinit() {
+    _prev_moon_rotation = -9999.0;
+}
+
+void FGTide::bind()
+{
+    SGPropertyNode *prop = globals->get_props();
+
+    _tideAnimation = prop->getNode("/environment/sea/surface/delta-T-tide", true);
+
+    _tideLevelNorm = prop->getNode("/sim/time/tide-level-norm", true);
+    _tideLevelNorm->setDoubleValue(_tide_level);
+}
+
+void FGTide::unbind()
+{
+    _tideLevelNorm.reset();
+    _tideAnimation.reset();
+}
+
+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 sun_rotation = _sunAngleRad->getDoubleValue();
+        _prev_moon_rotation = moon_rotation;
+
+        // 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);
+
+        _tideLevelNorm->setDoubleValue(_tide_level);
+        _tideAnimation->setDoubleValue(0.5 + 0.5*_tide_level);
+    }
+}
+
+// Register the subsystem.
+SGSubsystemMgr::Registrant<FGTide> registrantFGTide;

src/Time/tide.hxx

@@ -0,0 +1,62 @@
+// tide.hxx -- interface for tidal movement
+//
+// Written by Erik Hofman, Octover 2020
+//
+// Copyright (C) 2020  Erik Hofman <erik@ehofman.com>
+//
+// This program 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 2 of the
+// License, or (at your option) any later version.
+//
+// This program 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 this program; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+//
+
+#ifndef __FGTIDE_HXX
+#define __FGTIDE_HXX
+
+#ifndef __cplusplus
+# error This library requires C++
+#endif
+
+
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include <simgear/structure/subsystem_mgr.hxx>
+#include <simgear/props/tiedpropertylist.hxx>
+
+class FGTide : public SGSubsystem
+{
+public:
+    FGTide() = default;
+    virtual ~FGTide() = default;
+
+    // Subsystem API.
+    void bind() override;
+    void reinit() override;
+    void unbind() override;
+    void update(double dt) override;
+
+    // Subsystem identification.
+    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 _tide_level = 0;
+
+    SGPropertyNode_ptr _tideLevelNorm;
+    SGPropertyNode_ptr _tideAnimation;
+};
+
+#endif // __FGTIDE_HXX