Flight-path-history.

Record the historical flight-path (by default, since last takeoff). Optionally display the flight-path in the map; other visualisations (e.g., an 'in-world' view) could also be created. Nasal API to follow so Canvas-map or FMS can show the same data.

Altitude and attitude (Euler angles) are currently recorded but not used anywhere.

src/Aircraft/CMakeLists.txt

@@ -4,12 +4,14 @@ set(SOURCES
 	controls.cxx
 	replay.cxx
 	flightrecorder.cxx
+    FlightHistory.cxx
 	)
 
 set(HEADERS
 	controls.hxx
 	replay.hxx
 	flightrecorder.hxx
+    FlightHistory.hxx
 	)
 
 

src/Aircraft/FlightHistory.cxx

@@ -0,0 +1,166 @@
+// FlightHistory
+//
+// Written by James Turner, started December 2012.
+//
+// Copyright (C) 2012 James Turner - zakalawe (at) mac 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 St, Fifth Floor, Boston, MA  02110-1301, USA.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#include "FlightHistory.hxx"
+
+#include <algorithm>
+#include <boost/foreach.hpp>
+
+#include <simgear/sg_inlines.h>
+#include <simgear/debug/logstream.hxx>
+#include <simgear/props/props_io.hxx>
+#include <simgear/misc/strutils.hxx>
+#include <simgear/structure/exception.hxx>
+#include <simgear/math/SGMath.hxx>
+
+#include <Main/fg_props.hxx>
+#include <Main/globals.hxx>
+
+FGFlightHistory::FGFlightHistory() :
+    m_sampleInterval(5.0),
+    m_validSampleCount(SAMPLE_BUCKET_WIDTH)
+{
+}
+
+FGFlightHistory::~FGFlightHistory()
+{
+}
+
+void FGFlightHistory::init()
+{
+    m_sampleInterval = fgGetDouble("/sim/history/sample-interval-sec", 1.0);
+    if (m_sampleInterval <= 0.0) { // would be bad
+        SG_LOG(SG_FLIGHT, SG_INFO, "invalid flight-history sample interval:" << m_sampleInterval
+               << ", defaulting to " << m_sampleInterval);
+        m_sampleInterval = 1.0;
+    }
+    
+    m_weightOnWheels = NULL;
+// reset the history when we detect a take-off
+    if (fgGetBool("/sim/history/clear-on-takeoff", true)) {
+        m_weightOnWheels = fgGetNode("/gear/gear[1]/wow", 0, true);
+        m_lastWoW = m_weightOnWheels->getBoolValue();
+    }
+    
+    // force bucket re-allocation
+    m_validSampleCount = SAMPLE_BUCKET_WIDTH;
+}
+
+void FGFlightHistory::shutdown()
+{
+    clear();
+}
+
+void FGFlightHistory::reinit()
+{
+    shutdown();
+    init();
+}
+
+void FGFlightHistory::update(double dt)
+{
+    SG_UNUSED(dt); // we care about sim-time, not frame-time
+    
+    if (m_weightOnWheels) {
+        
+        if (m_lastWoW && !m_weightOnWheels->getBoolValue()) {
+            SG_LOG(SG_FLIGHT, SG_INFO, "history: detected main-gear takeoff, clearing history");
+            clear();
+        }
+    } // of rest-on-takeoff enabled
+    
+    double elapsed = globals->get_sim_time_sec() - m_lastCaptureTime;
+    if (elapsed > m_sampleInterval) {
+        capture();
+    }
+}
+
+void FGFlightHistory::allocateNewBucket()
+{
+    SampleBucket* bucket = new SampleBucket;
+    m_buckets.push_back(bucket);
+    m_validSampleCount = 0;
+}
+
+void FGFlightHistory::capture()
+{
+    if (m_validSampleCount == SAMPLE_BUCKET_WIDTH) {
+        // bucket is full, allocate a new one
+        allocateNewBucket();
+    }
+    
+    m_lastCaptureTime = globals->get_sim_time_sec();
+    Sample* sample = m_buckets.back()->samples + m_validSampleCount;
+    
+    sample->simTimeMSec = static_cast<int>(m_lastCaptureTime * 1000.0);
+    sample->position = globals->get_aircraft_position();
+    
+    double heading, pitch, roll;
+    globals->get_aircraft_orientation(heading, pitch, roll);
+    sample->heading = static_cast<float>(heading);
+    sample->pitch = static_cast<float>(pitch);
+    sample->roll = static_cast<float>(roll);
+    
+    ++m_validSampleCount;
+}
+
+SGGeodVec FGFlightHistory::pathForHistory(double minEdgeLengthM) const
+{
+    SGGeodVec result;
+    if (m_buckets.empty()) {
+        return result;
+    }
+    
+    result.push_back(m_buckets.front()->samples[0].position);
+    SGVec3d lastOutputCart = SGVec3d::fromGeod(result.back());
+    double minLengthSqr = minEdgeLengthM * minEdgeLengthM;
+    
+    BOOST_FOREACH(SampleBucket* bucket, m_buckets) {
+        unsigned int count = (bucket == m_buckets.back() ? m_validSampleCount : SAMPLE_BUCKET_WIDTH);
+    
+        // iterate over all the valid samples in the bucket
+        for (unsigned int index = 0; index < count; ++index) {
+            SGGeod g = bucket->samples[index].position;
+            SGVec3d cart(SGVec3d::fromGeod(g));
+            if (distSqr(cart, lastOutputCart) > minLengthSqr) {
+                lastOutputCart =  cart;
+                result.push_back(g);
+            }
+        } // of samples iteration
+    } // of buckets iteration
+    
+    return result;
+}
+
+void FGFlightHistory::clear()
+{
+    BOOST_FOREACH(SampleBucket* ptr, m_buckets) {
+        delete ptr;
+    }
+    m_buckets.clear();
+    m_validSampleCount = SAMPLE_BUCKET_WIDTH;
+}
+

src/Aircraft/FlightHistory.hxx

@@ -0,0 +1,105 @@
+// FlightHistory
+//
+// Written by James Turner, started December 2012.
+//
+// Copyright (C) 2012 James Turner - zakalawe (at) mac 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 St, Fifth Floor, Boston, MA  02110-1301, USA.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef FG_AIRCRAFT_FLIGHT_HISTORY_HXX
+#define FG_AIRCRAFT_FLIGHT_HISTORY_HXX
+
+#include <simgear/structure/subsystem_mgr.hxx>
+#include <simgear/props/props.hxx>
+#include <simgear/math/SGMath.hxx>
+
+#include <vector>
+#include <memory> // for std::auto_ptr
+
+typedef std::vector<SGGeod> SGGeodVec;
+
+/**
+ * record the history of the aircraft's movements, making it available
+ * as a contiguous block. This can be used to show the historical flight-path
+ * over a long period of time (unlike the replay system), but only a small,
+ * fixed set of properties are recorded. (Positioned and orientation, but
+ * not velocity, acceleration, control inputs, or so on)
+ */
+class FGFlightHistory : public SGSubsystem
+{
+public:
+    FGFlightHistory();
+    virtual ~FGFlightHistory();
+    
+    virtual void init();
+    virtual void shutdown();
+    virtual void reinit();
+    virtual void update(double dt);
+    
+    /**
+     * retrieve the path, collapsing segments shorter than
+     * the specified minimum length
+     */
+    SGGeodVec pathForHistory(double minEdgeLengthM = 50.0) const;
+private:
+    /**
+     * @class A single data sample in the history system.
+     */
+    class Sample
+    {
+    public:
+        SGGeod position;
+        /// heading, pitch and roll can be recorded at lower precision
+        /// than a double - actually 16 bits might be sufficient
+        float heading, pitch, roll;
+        int simTimeMSec;
+    };
+    
+    static const int SAMPLE_BUCKET_WIDTH = 1024;
+    
+    /**
+     * Bucket is a fixed-size container of samples. This is a crude slab
+     * allocation of samples, in chunks defined by the width constant above.
+     * Keep in mind that even with a 1Hz sample frequency, we use less than
+     * 200kbytes per hour - avoiding continous malloc traffic, or expensive
+     * std::vector reallocations, is the key factor here.
+     */
+    class SampleBucket
+    {
+    public:
+        Sample samples[SAMPLE_BUCKET_WIDTH];
+    };
+    
+    double m_lastCaptureTime;
+    double m_sampleInterval; ///< sample interval in seconds
+/// our store of samples (in buckets). The last bucket is partially full,
+/// with the number of valid samples indicated by m_validSampleCount
+    std::vector<SampleBucket*> m_buckets;
+    
+/// number of valid samples in the final bucket
+    unsigned int m_validSampleCount;
+    
+    SGPropertyNode_ptr m_weightOnWheels;
+    bool m_lastWoW;
+    
+    void allocateNewBucket();
+    
+    void clear();
+    void capture();
+};
+
+#endif

src/GUI/MapWidget.cxx

@@ -25,6 +25,7 @@
 #include <Airports/runways.hxx>
 #include <Main/fg_os.hxx>      // fgGetKeyModifiers()
 #include <Navaids/routePath.hxx>
+#include <Aircraft/FlightHistory.hxx>
 
 const char* RULER_LEGEND_KEY = "ruler-legend";
 
@@ -411,6 +412,7 @@ void MapWidget::setProperty(SGPropertyNode_ptr prop)
   _root->setIntValue("max-zoom", MAX_ZOOM);
   _root->setBoolValue("centre-on-aircraft", true);
   _root->setBoolValue("draw-data", false);
+  _root->setBoolValue("draw-flight-history", false);
   _root->setBoolValue("magnetic-headings", true);
 }
 
@@ -611,6 +613,7 @@ void MapWidget::draw(int dx, int dy)
   drawNavRadio(fgGetNode("/instrumentation/nav[0]", false));
   drawNavRadio(fgGetNode("/instrumentation/nav[1]", false));
   paintAircraftLocation(_aircraft);
+  drawFlightHistory();
   paintRoute();
   paintRuler();
 
@@ -748,6 +751,28 @@ void MapWidget::paintRoute()
   } // of second waypoint iteration
 }
 
+void MapWidget::drawFlightHistory()
+{
+  FGFlightHistory* history = (FGFlightHistory*) globals->get_subsystem("history");
+  if (!history || !_root->getBoolValue("draw-flight-history")) {
+    return;
+  }
+  
+  // first pass, draw the actual lines
+  glLineWidth(2.0);
+  
+  SGGeodVec gv(history->pathForHistory());
+  glColor4f(0.0, 0.0, 1.0, 0.7);
+
+  glBegin(GL_LINE_STRIP);
+  for (unsigned int i=0; i<gv.size(); ++i) {
+    SGVec2d p = project(gv[i]);
+    glVertex2d(p.x(), p.y());
+  }
+  
+  glEnd();
+}
+
 /**
  * Round a SGGeod to an arbitrary precision.
  * For example, passing precision of 0.5 will round to the nearest 0.5 of

src/GUI/MapWidget.hxx

@@ -43,6 +43,7 @@ private:
   void paintAircraftLocation(const SGGeod& aircraftPos);
   void paintRoute();
   void paintRuler();
+  void drawFlightHistory();
   
   void drawGPSData();
   void drawNavRadio(SGPropertyNode_ptr radio);

src/Main/fg_init.cxx

@@ -57,6 +57,7 @@
 
 #include <Aircraft/controls.hxx>
 #include <Aircraft/replay.hxx>
+#include <Aircraft/FlightHistory.hxx>
 #include <Airports/runways.hxx>
 #include <Airports/simple.hxx>
 #include <Airports/dynamics.hxx>
@@ -711,7 +712,8 @@ void fgCreateSubsystems() {
     // Initialize the replay subsystem
     ////////////////////////////////////////////////////////////////////
     globals->add_subsystem("replay", new FGReplay);
-
+    globals->add_subsystem("history", new FGFlightHistory);
+    
 #ifdef ENABLE_AUDIO_SUPPORT
     ////////////////////////////////////////////////////////////////////
     // Initialize the sound-effects subsystem.