Work on AIAircraft gear animation.

Inspired by Harald's patch, attempt to get AI models show realistic gear animations. Unfortunately AI models seem to be ignoring the gear properties, so keeping the code disabled until I can trace down why.

src/AIModel/AIAircraft.cxx

@@ -28,6 +28,7 @@
 #include <Scenery/tilemgr.hxx>
 #include <Airports/dynamics.hxx>
 #include <Airports/simple.hxx>
+#include <Main/util.hxx>
 
 #include <string>
 #include <math.h>
@@ -123,9 +124,6 @@ void FGAIAircraft::readFromScenario(SGPropertyNode* scFileNode) {
 void FGAIAircraft::bind() {
     FGAIBase::bind();
 
-    tie("controls/gear/gear-down",
-        SGRawValueMethods<FGAIAircraft,bool>(*this,
-                &FGAIAircraft::_getGearDown));
     tie("transponder-id",
         SGRawValueMethods<FGAIAircraft,const char*>(*this,
                 &FGAIAircraft::_getTransponderCode));
@@ -166,6 +164,12 @@ void FGAIAircraft::setPerformance(const std::string& acType, const std::string&
      handleATCRequests(); // ATC also has a word to say
      updateSecondaryTargetValues(); // target roll, vertical speed, pitch
      updateActualState();
+#if 0
+   // 25/11/12 - added but disabled, since setting properties isn't
+   // affecting the AI-model as expected.
+     updateModelProperties(dt);
+#endif
+   
     // We currently have one situation in which an AIAircraft object is used that is not attached to the
     // AI manager. In this particular case, the AIAircraft is used to shadow the user's aircraft's behavior in the AI world.
     // Since we perhaps don't want a radar entry of our own aircraft, the following conditional should probably be adequate
@@ -449,12 +453,6 @@ void FGAIAircraft::checkTcas(void)
 void FGAIAircraft::initializeFlightPlan() {
 }
 
-
-bool FGAIAircraft::_getGearDown() const {
-    return _performance->gearExtensible(this);
-}
-
-
 const char * FGAIAircraft::_getTransponderCode() const {
   return transponderCode.c_str();
 }
@@ -1375,3 +1373,44 @@ time_t FGAIAircraft::checkForArrivalTime(const string& wptName) {
      }
      return (ete - secondsToGo); // Positive when we're too slow...
 }
+
+double limitRateOfChange(double cur, double target, double maxDeltaSec, double dt)
+{
+  double delta = target - cur;
+  double maxDelta = maxDeltaSec * dt;
+  
+// if delta is > maxDelta, use maxDelta, but with the sign of delta.
+  return (fabs(delta) < maxDelta) ? delta : copysign(maxDelta, delta);
+}
+
+// drive various properties in a semi-realistic fashion.
+void FGAIAircraft::updateModelProperties(double dt)
+{
+  if (!props) {
+    return;
+  }
+  
+  SGPropertyNode* gear = props->getChild("gear", 0, true);
+  double targetGearPos = fp->getCurrentWaypoint()->getGear_down() ? 1.0 : 0.0;
+  if (!gear->hasValue("gear/position-norm")) {
+    gear->setDoubleValue("gear/position-norm", targetGearPos);
+  }
+  
+  double gearPosNorm = gear->getDoubleValue("gear/position-norm");
+  if (gearPosNorm != targetGearPos) {
+    gearPosNorm += limitRateOfChange(gearPosNorm, targetGearPos, 0.1, dt);
+    if (gearPosNorm < 0.001) {
+      gearPosNorm = 0.0;
+    } else if (gearPosNorm > 0.999) {
+      gearPosNorm = 1.0;
+    }
+    
+    for (int i=0; i<6; ++i) {
+      SGPropertyNode* g = gear->getChild("gear", i, true);
+      g->setDoubleValue("position-norm", gearPosNorm);
+    } // of gear setting loop      
+  } // of gear in-transit
+  
+//  double flapPosNorm = props->getDoubleValue();
+}
+

src/AIModel/AIAircraft.hxx

@@ -153,6 +153,7 @@ private:
     void updateVerticalSpeedTarget();
     void updatePitchAngleTarget();
     void updateActualState();
+    void updateModelProperties(double dt);
     void handleATCRequests();
     void checkVisibility();
     inline bool isStationary() { return ((fabs(speed)<=0.0001)&&(fabs(tgt_speed)<=0.0001));}
@@ -171,8 +172,6 @@ private:
 
     bool holdPos;
 
-    bool _getGearDown() const;
-
     const char * _getTransponderCode() const;
 
     bool reachedWaypoint;