AI: cache radar properties as nodes

When many AI objects, the cost of looking up the radar properties
for each object, each frame, is significant.

src/AIModel/AIBase.cxx

@@ -672,30 +672,24 @@ void FGAIBase::removeSoundFx() {
 
 double FGAIBase::UpdateRadar(FGAIManager* manager)
 {
-    bool control = fgGetBool("/sim/controls/radar", true);
+    if (!manager->isRadarEnabled())
+        return 0.0;
 
-    if(!control) return 0;
-
-    double radar_range_m = fgGetDouble("/instrumentation/radar/range");
-    bool force_on = fgGetBool("/instrumentation/radar/debug-mode", false);
-    radar_range_m *= SG_NM_TO_METER  * 1.1; // + 10%
-    radar_range_m *= radar_range_m; // squared
-
-    double d2 = distSqr(SGVec3d::fromGeod(pos), globals->get_aircraft_position_cart());
-    double range_ft = sqrt(d2) * SG_METER_TO_FEET;
-
-    if (!force_on && (d2 > radar_range_m)) {
-        return range_ft * range_ft;
+    const double radar_range_m = manager->radarRangeM() * 1.1; // + 10%
+    bool force_on = manager->enableRadarDebug();
+    double d = dist(SGVec3d::fromGeod(pos), globals->get_aircraft_position_cart());
+    double dFt = d * SG_METER_TO_FEET;
+    in_range = (d < radar_range_m);
+    
+    if (!force_on && in_range) {
+        return dFt * dFt;
     }
 
-    props->setBoolValue("radar/in-range", true);
-
     // copy values from the AIManager
     double user_heading   = manager->get_user_heading();
     double user_pitch     = manager->get_user_pitch();
 
-    range = range_ft * SG_FEET_TO_METER * SG_METER_TO_NM;
-
+    range = d * SG_METER_TO_NM;
     // calculate bearing to target
     bearing = SGGeodesy::courseDeg(globals->get_aircraft_position(), pos);
 
@@ -705,7 +699,7 @@ double FGAIBase::UpdateRadar(FGAIManager* manager)
 
     // calculate elevation to target
     ht_diff = altitude_ft - globals->get_aircraft_position().getElevationFt();
-    elevation = atan2( ht_diff, range_ft ) * SG_RADIANS_TO_DEGREES;
+    elevation = atan2( ht_diff, dFt ) * SG_RADIANS_TO_DEGREES;
 
     // calculate look up/down to target
     vert_offset = elevation - user_pitch;
@@ -731,7 +725,7 @@ double FGAIBase::UpdateRadar(FGAIManager* manager)
     rotation = hdg - user_heading;
     SG_NORMALIZE_RANGE(rotation, 0.0, 360.0);
 
-    return range_ft * range_ft;
+    return dFt * dFt;
 }
 
 /*

src/AIModel/AIManager.cxx

@@ -133,7 +133,8 @@ FGAIManager::init() {
     globals->get_commands()->addCommand("load-scenario", this, &FGAIManager::loadScenarioCommand);
     globals->get_commands()->addCommand("unload-scenario", this, &FGAIManager::unloadScenarioCommand);
     _environmentVisiblity = fgGetNode("/environment/visibility-m");
-
+    _groundSpeedKts_node = fgGetNode("/velocities/groundspeed-kt", true);
+    
     // Create an (invisible) AIAircraft representation of the current
     // users's aircraft, that mimicks the user aircraft's behavior.
 
@@ -142,7 +143,16 @@ FGAIManager::init() {
     _userAircraft->setGeodPos(globals->get_aircraft_position());
     _userAircraft->setPerformance("", "jet_transport");
     _userAircraft->setHeading(fgGetDouble("/orientation/heading-deg"));
-    _userAircraft->setSpeed(fgGetDouble("/velocities/groundspeed-kt"));
+    _userAircraft->setSpeed(_groundSpeedKts_node->getDoubleValue());
+    
+    // radar properties
+    _simRadarControl = fgGetNode("/sim/controls/radar", true);
+    if (!_simRadarControl->hasValue()) {
+        // default to true, but only if not already set
+        _simRadarControl->setBoolValue(true);
+    }
+    _radarRangeNode = fgGetNode("/instrumentation/radar/range", true);
+    _radarDebugNode = fgGetNode("/instrumentation/radar/debug-mode", true);
 }
 
 void
@@ -241,7 +251,12 @@ FGAIManager::update(double dt)
         return;
 
     fetchUserState(dt);
-
+    
+    // fetch radar state. Ensure we only do this once per frame.
+    _radarEnabled = _simRadarControl->getBoolValue();
+    _radarDebugMode = _radarDebugNode->getBoolValue();
+    _radarRangeM = _radarRangeNode->getDoubleValue() * SG_NM_TO_METER;
+    
     // partition the list into dead followed by alive
     auto firstAlive =
       std::stable_partition(ai_list.begin(), ai_list.end(), std::mem_fn(&FGAIBase::getDie));
@@ -348,7 +363,7 @@ FGAIManager::fetchUserState( double dt )
 
     _userAircraft->setGeodPos(globals->get_aircraft_position());
     _userAircraft->setHeading(user_heading);
-    _userAircraft->setSpeed(fgGetDouble("/velocities/groundspeed-kt"));
+    _userAircraft->setSpeed(_groundSpeedKts_node->getDoubleValue());
     _userAircraft->update(dt);
 }
 

src/AIModel/AIManager.hxx

@@ -92,6 +92,15 @@ public:
      * avoid correctly.
      */
     FGAIAircraft* getUserAircraft() const;
+    
+    bool isRadarEnabled() const
+    { return _radarEnabled; }
+    
+    bool enableRadarDebug() const
+    { return _radarDebugMode; }
+    
+    double radarRangeM() const
+    { return _radarRangeM; }
 private:
     // FGSubmodelMgr is a friend for access to the AI_list
     friend class FGSubmodelMgr;
@@ -120,7 +129,8 @@ private:
     SGPropertyNode_ptr wind_from_east_node;
     SGPropertyNode_ptr wind_from_north_node;
     SGPropertyNode_ptr _environmentVisiblity;
-
+    SGPropertyNode_ptr _groundSpeedKts_node;
+    
     ai_list_type ai_list;
 
     double user_altitude_agl;
@@ -146,6 +156,12 @@ private:
     ScenarioDict _scenarios;
 
     SGSharedPtr<FGAIAircraft> _userAircraft;
+    
+    SGPropertyNode_ptr _simRadarControl,
+        _radarRangeNode, _radarDebugNode;
+    bool _radarEnabled = true,
+        _radarDebugMode = false;
+    double _radarRangeM = 0.0;
 };
 
 #endif  // _FG_AIMANAGER_HXX