refs #852 Use X-Plane terrain probe to provide ground elevation to the interpolator.

src/xbus/terrainprobe.cpp

@@ -0,0 +1,36 @@
+/* Copyright (C) 2017
+ * swift Project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+#include "terrainprobe.h"
+#include <XPLM/XPLMGraphics.h>
+#include <limits>
+
+namespace XBus
+{
+    CTerrainProbe::CTerrainProbe() : m_ref(XPLMCreateProbe(xplm_ProbeY)) {}
+
+    CTerrainProbe::~CTerrainProbe() { XPLMDestroyProbe(m_ref); }
+
+    double CTerrainProbe::getElevation(double degreesLatitude, double degreesLongitude, double metersAltitude) const
+    {
+        double x, y, z;
+        XPLMWorldToLocal(degreesLatitude, degreesLongitude, metersAltitude, &x, &y, &z);
+
+        XPLMProbeInfo_t probe;
+        probe.structSize = sizeof(probe);
+        auto result = XPLMProbeTerrainXYZ(m_ref, static_cast<float>(x), static_cast<float>(y), static_cast<float>(z), &probe);
+        if (result != xplm_ProbeHitTerrain)
+        {
+            return std::numeric_limits<double>::quiet_NaN();
+        }
+
+        XPLMLocalToWorld(probe.locationX, probe.locationY, probe.locationZ, &degreesLatitude, &degreesLongitude, &metersAltitude);
+        return metersAltitude;
+    }
+}

src/xbus/terrainprobe.h

@@ -0,0 +1,39 @@
+/* Copyright (C) 2017
+ * swift Project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+#ifndef BLACKSIM_XBUS_ELEVATIONPROVIDER_H
+#define BLACKSIM_XBUS_ELEVATIONPROVIDER_H
+
+#include <XPLM/XPLMScenery.h>
+
+namespace XBus
+{
+    /*!
+     * Class based interface to X-Plane SDK terrain probe.
+     */
+    class CTerrainProbe
+    {
+    public:
+        //! Constructor.
+        CTerrainProbe();
+
+        //! Destructor;
+        ~CTerrainProbe();
+
+        //! Get the elevation in meters at the given point in OpenGL space.
+        //! \note Due to the Earth's curvature, the OpenGL vertical axis may not be exactly perpendicular to the surface of the geoid.
+        //! \return NaN if no ground was detected.
+        double getElevation(double degreesLatitude, double degreesLongitude, double metersAltitude) const;
+
+    private:
+        XPLMProbeRef m_ref = nullptr;
+    };
+}
+
+#endif

src/xbus/traffic.cpp

@@ -42,6 +42,23 @@ namespace XBus
         surfaces.lights.timeOffset = static_cast<quint16>(qrand() % 0xffff);
     }
 
+    BlackMisc::Simulation::CInterpolationHints CTraffic::Plane::hints(BlackMisc::Simulation::IInterpolator *interpolator) const
+    {
+        BlackMisc::Simulation::CInterpolationHints hints;
+        BlackMisc::Simulation::IInterpolator::PartsStatus status;
+        hints.setAircraftParts(interpolator->getInterpolatedParts(parts, -1, status));
+        hints.setElevationProvider([this](const auto &situation)
+        {
+            using namespace BlackMisc::PhysicalQuantities;
+            const auto meters = terrainProbe.getElevation(situation.latitude().value(CAngleUnit::deg()),
+                                                          situation.longitude().value(CAngleUnit::deg()),
+                                                          situation.getAltitude().value(CLengthUnit::m()));
+            if (std::isnan(meters)) { return CLength(0, nullptr); }
+            return CLength(meters, CLengthUnit::m());
+        });
+        return hints;
+    }
+
     CTraffic::CTraffic(QObject *parent) :
         QObject(parent),
         m_interpolator(new BlackMisc::Simulation::CInterpolatorLinear(new BlackMisc::Simulation::CRemoteAircraftProviderDummy(this), this))
@@ -316,8 +333,7 @@ namespace XBus
         case xpmpDataType_Position:
             {
                 BlackMisc::Simulation::IInterpolator::InterpolationStatus status;
-                const BlackMisc::Simulation::CInterpolationHints hints;
-                const auto situation = m_interpolator->getInterpolatedSituation(plane->situations, -1, hints, status);
+                const auto situation = m_interpolator->getInterpolatedSituation(plane->situations, -1, plane->hints(m_interpolator), status);
                 if (! status.didInterpolationSucceed()) { return xpmpData_Unavailable; }
                 if (! status.hasChangedPosition()) { return xpmpData_Unchanged; }
 

src/xbus/traffic.h

@@ -13,6 +13,7 @@
 //! \file
 
 #include "datarefs.h"
+#include "terrainprobe.h"
 #include "blackmisc/aviation/aircraftsituationlist.h"
 #include "blackmisc/aviation/aircraftpartslist.h"
 #include <QObject>
@@ -26,7 +27,14 @@
 #define XBUS_TRAFFIC_OBJECTPATH "/xbus/traffic"
 //! \endcond
 
-namespace BlackMisc { namespace Simulation { class IInterpolator; } }
+namespace BlackMisc
+{
+    namespace Simulation
+    {
+        class IInterpolator;
+        class CInterpolationHints;
+    }
+}
 namespace XBus
 {
     /*!
@@ -131,6 +139,8 @@ namespace XBus
             char label[32] {};
             BlackMisc::Aviation::CAircraftSituationList situations;
             BlackMisc::Aviation::CAircraftPartsList parts;
+            CTerrainProbe terrainProbe;
+            BlackMisc::Simulation::CInterpolationHints hints(BlackMisc::Simulation::IInterpolator *) const;
             XPMPPlaneSurfaces_t surfaces;
             XPMPPlaneRadar_t xpdr;
             Plane(void *id_, QString callsign_, QString aircraftIcao_, QString airlineIcao_, QString livery_);