]> git.mxchange.org Git - flightgear.git/blobdiff - src/FDM/groundcache.cxx
Unified handling of (fuel-)tank properties
[flightgear.git] / src / FDM / groundcache.cxx
index 450b53ef81c6866cd20d7808805333cd113fe5a1..9d83e283e2c1474a27d7c68e138b63d7ce8cf636 100644 (file)
@@ -2,7 +2,7 @@
 //
 // Written by Mathias Froehlich, started Nov 2004.
 //
-// Copyright (C) 2004  Mathias Froehlich - Mathias.Froehlich@web.de
+// Copyright (C) 2004, 2009  Mathias Froehlich - Mathias.Froehlich@web.de
 //
 // This program is free software; you can redistribute it and/or
 // modify it under the terms of the GNU General Public License as
 //
 // 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 //
 // $Id$
 
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
 
-#include <float.h>
+#include "groundcache.hxx"
+
+#include <utility>
 
-#include <plib/sg.h>
+#include <osg/Drawable>
+#include <osg/Geode>
+#include <osg/Geometry>
+#include <osg/Camera>
+#include <osg/Transform>
+#include <osg/MatrixTransform>
+#include <osg/PositionAttitudeTransform>
+#include <osg/CameraView>
 
 #include <simgear/sg_inlines.h>
 #include <simgear/constants.h>
 #include <simgear/debug/logstream.hxx>
-#include <simgear/math/sg_geodesy.hxx>
+#include <simgear/math/SGMisc.hxx>
+#include <simgear/scene/util/SGNodeMasks.hxx>
+#include <simgear/scene/util/SGSceneUserData.hxx>
+
+#include <simgear/scene/bvh/BVHNode.hxx>
+#include <simgear/scene/bvh/BVHGroup.hxx>
+#include <simgear/scene/bvh/BVHTransform.hxx>
+#include <simgear/scene/bvh/BVHMotionTransform.hxx>
+#include <simgear/scene/bvh/BVHLineGeometry.hxx>
+#include <simgear/scene/bvh/BVHStaticGeometry.hxx>
+#include <simgear/scene/bvh/BVHStaticData.hxx>
+#include <simgear/scene/bvh/BVHStaticNode.hxx>
+#include <simgear/scene/bvh/BVHStaticTriangle.hxx>
+#include <simgear/scene/bvh/BVHStaticBinary.hxx>
+#include <simgear/scene/bvh/BVHSubTreeCollector.hxx>
+#include <simgear/scene/bvh/BVHLineSegmentVisitor.hxx>
+#include <simgear/scene/bvh/BVHNearestPointVisitor.hxx>
+
+#ifdef GROUNDCACHE_DEBUG
+#include <simgear/scene/bvh/BVHDebugCollectVisitor.hxx>
+#include <Main/fg_props.hxx>
+#endif
 
 #include <Main/globals.hxx>
 #include <Scenery/scenery.hxx>
 #include <Scenery/tilemgr.hxx>
-#include <AIModel/AICarrier.hxx>
 
 #include "flight.hxx"
-#include "groundcache.hxx"
 
-// Specialized version of sgMultMat4 needed because of mixed matrix
-// types
-static inline void fgMultMat4(sgdMat4 dst, sgdMat4 m1, sgMat4 m2) {
-    for ( int j = 0 ; j < 4 ; j++ ) {
-        dst[0][j] = m2[0][0] * m1[0][j] +
-                    m2[0][1] * m1[1][j] +
-                    m2[0][2] * m1[2][j] +
-                    m2[0][3] * m1[3][j] ;
-
-        dst[1][j] = m2[1][0] * m1[0][j] +
-                    m2[1][1] * m1[1][j] +
-                    m2[1][2] * m1[2][j] +
-                    m2[1][3] * m1[3][j] ;
-
-        dst[2][j] = m2[2][0] * m1[0][j] +
-                    m2[2][1] * m1[1][j] +
-                    m2[2][2] * m1[2][j] +
-                    m2[2][3] * m1[3][j] ;
-
-        dst[3][j] = m2[3][0] * m1[0][j] +
-                    m2[3][1] * m1[1][j] +
-                    m2[3][2] * m1[2][j] +
-                    m2[3][3] * m1[3][j] ;
+using namespace simgear;
+
+class FGGroundCache::CacheFill : public osg::NodeVisitor {
+public:
+    CacheFill(const SGVec3d& center, const SGVec3d& down, const double& radius,
+              const double& startTime, const double& endTime) :
+        osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ACTIVE_CHILDREN),
+        _center(center),
+        _down(down),
+        _radius(radius),
+        _startTime(startTime),
+        _endTime(endTime),
+        _sceneryHit(0, 0, 0),
+        _maxDown(SGGeod::fromCart(center).getElevationM() + 9999),
+        _material(0),
+        _haveHit(false)
+    {
+        setTraversalMask(SG_NODEMASK_TERRAIN_BIT);
     }
-}
-
-static inline bool fgdPointInTriangle( sgdVec3 point, sgdVec3 tri[3] )
-{
-    sgdVec3 dif;
-
-    // Some tolerance in meters we accept a point to be outside of the triangle
-    // and still return that it is inside.
-    SGDfloat eps = 1e-2;
-    SGDfloat min, max;
-    // punt if outside bouding cube
-    SG_MIN_MAX3 ( min, max, tri[0][0], tri[1][0], tri[2][0] );
-    if( (point[0] < min - eps) || (point[0] > max + eps) )
-        return false;
-    dif[0] = max - min;
+    virtual void apply(osg::Node& node)
+    {
+        if (!testBoundingSphere(node.getBound()))
+            return;
 
-    SG_MIN_MAX3 ( min, max, tri[0][1], tri[1][1], tri[2][1] );
-    if( (point[1] < min - eps) || (point[1] > max + eps) )
-        return false;
-    dif[1] = max - min;
+        addBoundingVolume(node);
+    }
+    
+    virtual void apply(osg::Group& group)
+    {
+        if (!testBoundingSphere(group.getBound()))
+            return;
 
-    SG_MIN_MAX3 ( min, max, tri[0][2], tri[1][2], tri[2][2] );
-    if( (point[2] < min - eps) || (point[2] > max + eps) )
-        return false;
-    dif[2] = max - min;
-
-    // drop the smallest dimension so we only have to work in 2d.
-    SGDfloat min_dim = SG_MIN3 (dif[0], dif[1], dif[2]);
-    SGDfloat x1, y1, x2, y2, x3, y3, rx, ry;
-    if ( fabs(min_dim-dif[0]) <= DBL_EPSILON ) {
-        // x is the smallest dimension
-        x1 = point[1];
-        y1 = point[2];
-        x2 = tri[0][1];
-        y2 = tri[0][2];
-        x3 = tri[1][1];
-        y3 = tri[1][2];
-        rx = tri[2][1];
-        ry = tri[2][2];
-    } else if ( fabs(min_dim-dif[1]) <= DBL_EPSILON ) {
-        // y is the smallest dimension
-        x1 = point[0];
-        y1 = point[2];
-        x2 = tri[0][0];
-        y2 = tri[0][2];
-        x3 = tri[1][0];
-        y3 = tri[1][2];
-        rx = tri[2][0];
-        ry = tri[2][2];
-    } else if ( fabs(min_dim-dif[2]) <= DBL_EPSILON ) {
-        // z is the smallest dimension
-        x1 = point[0];
-        y1 = point[1];
-        x2 = tri[0][0];
-        y2 = tri[0][1];
-        x3 = tri[1][0];
-        y3 = tri[1][1];
-        rx = tri[2][0];
-        ry = tri[2][1];
-    } else {
-        // all dimensions are really small so lets call it close
-        // enough and return a successful match
-        return true;
+        simgear::BVHSubTreeCollector::NodeList parentNodeList;
+        mSubTreeCollector.pushNodeList(parentNodeList);
+        
+        traverse(group);
+        addBoundingVolume(group);
+        
+        mSubTreeCollector.popNodeList(parentNodeList);
     }
+    
+    virtual void apply(osg::Transform& transform)
+    { handleTransform(transform); }
+    virtual void apply(osg::Camera& camera)
+    {
+        if (camera.getRenderOrder() != osg::Camera::NESTED_RENDER)
+            return;
+        handleTransform(camera);
+    }
+    virtual void apply(osg::CameraView& transform)
+    { handleTransform(transform); }
+    virtual void apply(osg::MatrixTransform& transform)
+    { handleTransform(transform); }
+    virtual void apply(osg::PositionAttitudeTransform& transform)
+    { handleTransform(transform); }
+        
+    void handleTransform(osg::Transform& transform)
+    {
+        // Hmm, may be this needs to be refined somehow ...
+        if (transform.getReferenceFrame() != osg::Transform::RELATIVE_RF)
+            return;
+
+        if (!testBoundingSphere(transform.getBound()))
+            return;
+
+        osg::Matrix inverseMatrix;
+        if (!transform.computeWorldToLocalMatrix(inverseMatrix, this))
+            return;
+        osg::Matrix matrix;
+        if (!transform.computeLocalToWorldMatrix(matrix, this))
+            return;
+
+        // Look for a velocity note
+        const SGSceneUserData::Velocity* velocity = getVelocity(transform);
+
+        SGVec3d center = _center;
+        SGVec3d down = _down;
+        double radius = _radius;
+        bool haveHit = _haveHit;
+        const SGMaterial* material = _material;
+
+        _haveHit = false;
+        _center = toSG(inverseMatrix.preMult(toOsg(_center)));
+        _down = toSG(osg::Matrix::transform3x3(toOsg(_down), inverseMatrix));
+        if (velocity) {
+            SGVec3d staticCenter(_center);
+
+            double dtStart = velocity->referenceTime - _startTime;
+            SGVec3d startCenter = staticCenter + dtStart*velocity->linear;
+            SGQuatd startOr(SGQuatd::fromAngleAxis(dtStart*velocity->angular));
+            startCenter = startOr.transform(startCenter);
+            
+            double dtEnd = velocity->referenceTime - _endTime;
+            SGVec3d endCenter = staticCenter + dtEnd*velocity->linear;
+            SGQuatd endOr(SGQuatd::fromAngleAxis(dtEnd*velocity->angular));
+            endCenter = endOr.transform(endCenter);
+
+            _center = 0.5*(startCenter + endCenter);
+            _down = startOr.transform(_down);
+            _radius += 0.5*dist(startCenter, endCenter);
+        }
+        
+        simgear::BVHSubTreeCollector::NodeList parentNodeList;
+        mSubTreeCollector.pushNodeList(parentNodeList);
+
+        addBoundingVolume(transform);
+        traverse(transform);
+
+        if (mSubTreeCollector.haveChildren()) {
+            if (velocity) {
+                simgear::BVHMotionTransform* bvhTransform;
+                bvhTransform = new simgear::BVHMotionTransform;
+                bvhTransform->setToWorldTransform(SGMatrixd(matrix.ptr()));
+                bvhTransform->setLinearVelocity(velocity->linear);
+                bvhTransform->setAngularVelocity(velocity->angular);
+                bvhTransform->setReferenceTime(velocity->referenceTime);
+                bvhTransform->setStartTime(_startTime);
+                bvhTransform->setEndTime(_endTime);
+                bvhTransform->setId(velocity->id);
+
+                mSubTreeCollector.popNodeList(parentNodeList, bvhTransform);
+            } else {
+                simgear::BVHTransform* bvhTransform;
+                bvhTransform = new simgear::BVHTransform;
+                bvhTransform->setToWorldTransform(SGMatrixd(matrix.ptr()));
+
+                mSubTreeCollector.popNodeList(parentNodeList, bvhTransform);
+            }
+        } else {
+            mSubTreeCollector.popNodeList(parentNodeList);
+        }
 
-    // check if intersection point is on the same side of p1 <-> p2 as p3
-    SGDfloat tmp = (y2 - y3);
-    SGDfloat tmpn = (x2 - x3);
-    int side1 = SG_SIGN (tmp * (rx - x3) + (y3 - ry) * tmpn);
-    int side2 = SG_SIGN (tmp * (x1 - x3) + (y3 - y1) * tmpn
-                         + side1 * eps * fabs(tmpn));
-    if ( side1 != side2 ) {
-        // printf("failed side 1 check\n");
-        return false;
+        if (_haveHit) {
+            if (velocity) {
+                double dt = _startTime - velocity->referenceTime;
+                SGQuatd ori(SGQuatd::fromAngleAxis(dt*velocity->angular));
+                _sceneryHit = ori.transform(_sceneryHit);
+                _sceneryHit += dt*velocity->linear;
+            }
+            _sceneryHit = toSG(matrix.preMult(toOsg(_sceneryHit)));
+        } else {
+            _material = material;
+            _haveHit = haveHit;
+        }
+
+        _center = center;
+        _down = down;
+        _radius = radius;
     }
 
-    // check if intersection point is on correct side of p2 <-> p3 as p1
-    tmp = (y3 - ry);
-    tmpn = (x3 - rx);
-    side1 = SG_SIGN (tmp * (x2 - rx) + (ry - y2) * tmpn);
-    side2 = SG_SIGN (tmp * (x1 - rx) + (ry - y1) * tmpn
-                     + side1 * eps * fabs(tmpn));
-    if ( side1 != side2 ) {
-        // printf("failed side 2 check\n");
-        return false;
+    const SGSceneUserData::Velocity* getVelocity(osg::Node& node)
+    {
+        SGSceneUserData* userData = SGSceneUserData::getSceneUserData(&node);
+        if (!userData)
+            return 0;
+        return userData->getVelocity();
+    }
+    simgear::BVHNode* getNodeBoundingVolume(osg::Node& node)
+    {
+        SGSceneUserData* userData = SGSceneUserData::getSceneUserData(&node);
+        if (!userData)
+            return 0;
+        return userData->getBVHNode();
     }
+    void addBoundingVolume(osg::Node& node)
+    {
+        simgear::BVHNode* bvNode = getNodeBoundingVolume(node);
+        if (!bvNode)
+            return;
+
+        // Find a croase ground intersection 
+        SGLineSegmentd line(_center + _radius*_down, _center + _maxDown*_down);
+        simgear::BVHLineSegmentVisitor lineSegmentVisitor(line, _startTime);
+        bvNode->accept(lineSegmentVisitor);
+        if (!lineSegmentVisitor.empty()) {
+            _sceneryHit = lineSegmentVisitor.getPoint();
+            _material = lineSegmentVisitor.getMaterial();
+            _maxDown = SGMiscd::max(_radius, dot(_down, _sceneryHit - _center));
+            _haveHit = true;
+        }
 
-    // check if intersection point is on correct side of p1 <-> p3 as p2
-    tmp = (y2 - ry);
-    tmpn = (x2 - rx);
-    side1 = SG_SIGN (tmp * (x3 - rx) + (ry - y3) * tmpn);
-    side2 = SG_SIGN (tmp * (x1 - rx) + (ry - y1) * tmpn
-                     + side1 * eps * fabs(tmpn));
-    if ( side1 != side2 ) {
-        // printf("failed side 3  check\n");
-        return false;
+        // Get that part of the local bv tree that intersects our sphere
+        // of interrest.
+        mSubTreeCollector.setSphere(SGSphered(_center, _radius));
+        bvNode->accept(mSubTreeCollector);
     }
+    
+    bool testBoundingSphere(const osg::BoundingSphere& bound) const
+    {
+        if (!bound.valid())
+            return false;
+
+        SGLineSegmentd downSeg(_center, _center + _maxDown*_down);
+        double maxDist = bound._radius + _radius;
+        SGVec3d boundCenter(toVec3d(toSG(bound._center)));
+        return distSqr(downSeg, boundCenter) <= maxDist*maxDist;
+    }
+    
+    SGSharedPtr<simgear::BVHNode> getBVHNode() const
+    { return mSubTreeCollector.getNode(); }
+
+    bool getHaveElevationBelowCache() const
+    { return _haveHit; }
+    double getElevationBelowCache() const
+    { return SGGeod::fromCart(_sceneryHit).getElevationM(); }
+    const SGMaterial* getMaterialBelowCache() const
+    { return _material; }
+    
+private:
+    SGVec3d _center;
+    SGVec3d _down;
+    double _radius;
+    double _startTime;
+    double _endTime;
+
+    simgear::BVHSubTreeCollector mSubTreeCollector;
+    SGVec3d _sceneryHit;
+    double _maxDown;
+    const SGMaterial* _material;
+    bool _haveHit;
+};
+
+FGGroundCache::FGGroundCache() :
+    _altitude(0),
+    _material(0),
+    cache_ref_time(0),
+    cache_time_offset(0),
+    _wire(0),
+    reference_wgs84_point(SGVec3d(0, 0, 0)),
+    reference_vehicle_radius(0),
+    down(0.0, 0.0, 0.0),
+    found_ground(false)
+{
+#ifdef GROUNDCACHE_DEBUG
+    _lookupTime = SGTimeStamp::fromSec(0.0);
+    _lookupCount = 0;
+    _buildTime = SGTimeStamp::fromSec(0.0);
+    _buildCount = 0;
+#endif
+}
 
-    return true;
+FGGroundCache::~FGGroundCache()
+{
 }
 
-// Test if the line given by the point on the line pt_on_line and the
-// line direction dir intersects the sphere sp.
-// Adapted from plib.
-static inline bool
-fgdIsectSphereInfLine(const sgdSphere& sp,
-                      const sgdVec3 pt_on_line, const sgdVec3 dir)
+bool
+FGGroundCache::prepare_ground_cache(double startSimTime, double endSimTime,
+                                    const SGVec3d& pt, double rad)
 {
-  sgdVec3 r;
-  sgdSubVec3( r, sp.getCenter(), pt_on_line ) ;
+#ifdef GROUNDCACHE_DEBUG
+    SGTimeStamp t0 = SGTimeStamp::now();
+#endif
+
+    // Empty cache.
+    found_ground = false;
+
+    SGGeod geodPt = SGGeod::fromCart(pt);
+    // Don't blow away the cache ground_radius and stuff if there's no
+    // scenery
+    if (!globals->get_tile_mgr()->schedule_scenery(geodPt, rad, 1.0)) {
+        SG_LOG(SG_FLIGHT, SG_WARN, "prepare_ground_cache(): scenery_available "
+               "returns false at " << geodPt << " " << pt << " " << rad);
+        return false;
+    }
+    _material = 0;
 
-  SGDfloat projectedDistance = sgdScalarProductVec3(r, dir);
-  SGDfloat dist = sgdScalarProductVec3 ( r, r ) -
-    projectedDistance * projectedDistance;
+    // If we have an active wire, get some more area into the groundcache
+    if (_wire)
+        rad = SGMiscd::max(200, rad);
+    
+    // Store the parameters we used to build up that cache.
+    reference_wgs84_point = pt;
+    reference_vehicle_radius = rad;
+    // Store the time reference used to compute movements of moving triangles.
+    cache_ref_time = startSimTime;
+    
+    // Get a normalized down vector valid for the whole cache
+    SGQuatd hlToEc = SGQuatd::fromLonLat(geodPt);
+    down = hlToEc.rotate(SGVec3d(0, 0, 1));
+    
+    // Get the ground cache, that is a local collision tree of the environment
+    startSimTime += cache_time_offset;
+    endSimTime += cache_time_offset;
+    CacheFill subtreeCollector(pt, down, rad, startSimTime, endSimTime);
+    globals->get_scenery()->get_scene_graph()->accept(subtreeCollector);
+    _localBvhTree = subtreeCollector.getBVHNode();
+
+    if (subtreeCollector.getHaveElevationBelowCache()) {
+        // Use the altitude value below the cache that we gathered during
+        // cache collection
+        _altitude = subtreeCollector.getElevationBelowCache();
+        _material = subtreeCollector.getMaterialBelowCache();
+        found_ground = true;
+    } else if (_localBvhTree) {
+        // We have nothing below us, so try starting with the lowest point
+        // upwards for a croase altitude value
+        SGLineSegmentd line(pt + reference_vehicle_radius*down, pt - 1e3*down);
+        simgear::BVHLineSegmentVisitor lineSegmentVisitor(line, startSimTime);
+        _localBvhTree->accept(lineSegmentVisitor);
+
+        if (!lineSegmentVisitor.empty()) {
+            SGGeod geodPt = SGGeod::fromCart(lineSegmentVisitor.getPoint());
+            _altitude = geodPt.getElevationM();
+            _material = lineSegmentVisitor.getMaterial();
+            found_ground = true;
+        }
+    }
+    
+    if (!found_ground) {
+        // Ok, still nothing here?? Last resort ...
+        double alt = 0;
+        found_ground = globals->get_scenery()->
+            get_elevation_m(SGGeod::fromGeodM(geodPt, 10000), alt, &_material);
+        if (found_ground)
+            _altitude = alt;
+    }
+    
+    // Still not sucessful??
+    if (!found_ground)
+        SG_LOG(SG_FLIGHT, SG_WARN, "prepare_ground_cache(): trying to build "
+               "cache without any scenery below the aircraft");
+
+#ifdef GROUNDCACHE_DEBUG
+    t0 = SGTimeStamp::now() - t0;
+    _buildTime += t0;
+    _buildCount++;
+
+    if (_buildCount > 60) {
+        double buildTime = 0;
+        if (_buildCount)
+            buildTime = _buildTime.toSecs()/_buildCount;
+        double lookupTime = 0;
+        if (_lookupCount)
+            lookupTime = _lookupTime.toSecs()/_lookupCount;
+        _buildTime = SGTimeStamp::fromSec(0.0);
+        _buildCount = 0;
+        _lookupTime = SGTimeStamp::fromSec(0.0);
+        _lookupCount = 0;
+        SG_LOG(SG_FLIGHT, SG_ALERT, "build time = " << buildTime
+               << ", lookup Time = " << lookupTime);
+    }
 
-  SGDfloat radius = sp.getRadius();
-  return dist < radius*radius;
-}
+    if (!_group.valid()) {
+        _group = new osg::Group;
+        globals->get_scenery()->get_scene_graph()->addChild(_group);
+        fgSetInt("/fdm/groundcache-debug-level", -3);
+    }
+    _group->removeChildren(0, _group->getNumChildren());
+    if (_localBvhTree) {
+        int level = fgGetInt("/fdm/groundcache-debug-level");
+        if (-2 <= level) {
+            simgear::BVHDebugCollectVisitor debug(endSimTime, level);
+            _localBvhTree->accept(debug);
+            _group->addChild(debug.getNode());
+        }
+    }
+#endif
 
-FGGroundCache::FGGroundCache()
-{
-  sgdSetVec3(cache_center, 0.0, 0.0, 0.0);
-  ground_radius = 0.0;
-  cache_ref_time = 0.0;
-  wire_id = 0;
-  sgdSetVec3(reference_wgs84_point, 0.0, 0.0, 0.0);
-  reference_vehicle_radius = 0.0;
-  found_ground = false;
+    return found_ground;
 }
 
-FGGroundCache::~FGGroundCache()
+bool
+FGGroundCache::is_valid(double& ref_time, SGVec3d& pt, double& rad)
 {
+    pt = reference_wgs84_point;
+    rad = reference_vehicle_radius;
+    ref_time = cache_ref_time;
+    return found_ground;
 }
 
-FGGroundCache::GroundProperty
-FGGroundCache::extractGroundProperty( ssgLeaf* l )
-{
-  // FIXME: Do more ...
-  // Idea: have a get_globals() function which knows about that stuff.
-  // Or most propably read that from a configuration file,
-  // from property tree or whatever ...
-  
-  // Get ground dependent data.
-  GroundProperty gp;
-  gp.wire_id = -1;
-  
-  FGAICarrierHardware *ud =
-    dynamic_cast<FGAICarrierHardware*>(l->getUserData());
-  if (ud) {
-    switch (ud->type) {
-    case FGAICarrierHardware::Wire:
-      gp.type = FGInterface::Wire;
-      gp.wire_id = ud->id;
-      break;
-    case FGAICarrierHardware::Catapult:
-      gp.type = FGInterface::Catapult;
-      break;
-    default:
-      gp.type = FGInterface::Solid;
-      break;
-    }
-
-    // Copy the velocity from the carrier class.
-    ud->carrier->getVelocityWrtEarth( gp.vel, gp.rot, gp.pivot );
-  }
-
-  else {
-
-    // Initialize velocity field.
-    sgdSetVec3( gp.vel, 0.0, 0.0, 0.0 );
-    sgdSetVec3( gp.rot, 0.0, 0.0, 0.0 );
-    sgdSetVec3( gp.pivot, 0.0, 0.0, 0.0 );
-  }
-  
-  // Get the texture name and decide what ground type we have.
-  ssgState *st = l->getState();
-  if (st != NULL && st->isAKindOf(ssgTypeSimpleState())) {
-    ssgSimpleState *ss = (ssgSimpleState*)st;
-    SGPath fullPath( ss->getTextureFilename() ? ss->getTextureFilename(): "" );
-    string file = fullPath.file();
-    SGPath dirPath(fullPath.dir());
-    string category = dirPath.file();
-    
-    if (category == "Runway")
-      gp.type = FGInterface::Solid;
-    else {
-      if (file == "asphault.rgb" || file == "airport.rgb")
-        gp.type = FGInterface::Solid;
-      else if (file == "water.rgb" || file == "water-lake.rgb")
-        gp.type = FGInterface::Water;
-      else if (file == "forest.rgb" || file == "cropwood.rgb")
-        gp.type = FGInterface::Forest;
-    }
-  }
-  
-  return gp;
-}
+class FGGroundCache::BodyFinder : public BVHVisitor {
+public:
+    BodyFinder(BVHNode::Id id, const double& t) :
+        _id(id),
+        _bodyToWorld(SGMatrixd::unit()),
+        _linearVelocity(0, 0, 0),
+        _angularVelocity(0, 0, 0),
+        _time(t)
+    { }
+    
+    virtual void apply(BVHGroup& leaf)
+    {
+        if (_foundId)
+            return;
+        leaf.traverse(*this);
+    }
+    virtual void apply(BVHTransform& transform)
+    {
+        if (_foundId)
+            return;
+
+        transform.traverse(*this);
+        
+        if (_foundId) {
+            _linearVelocity = transform.vecToWorld(_linearVelocity);
+            _angularVelocity = transform.vecToWorld(_angularVelocity);
+            _bodyToWorld = transform.getToWorldTransform()*_bodyToWorld;
+        }
+    }
+    virtual void apply(BVHMotionTransform& transform)
+    {
+        if (_foundId)
+            return;
+
+        if (_id == transform.getId()) {
+            _foundId = true;
+        } else {
+            transform.traverse(*this);
+        }
+        
+        if (_foundId) {
+            SGMatrixd toWorld = transform.getToWorldTransform(_time);
+            SGVec3d referencePoint = _bodyToWorld.xformPt(SGVec3d::zeros());
+            _linearVelocity += transform.getLinearVelocityAt(referencePoint);
+            _angularVelocity += transform.getAngularVelocity();
+            _linearVelocity = toWorld.xformVec(_linearVelocity);
+            _angularVelocity = toWorld.xformVec(_angularVelocity);
+            _bodyToWorld = toWorld*_bodyToWorld;
+        }
+    }
+    virtual void apply(BVHLineGeometry& node) { }
+    virtual void apply(BVHStaticGeometry& node) { }
+    
+    virtual void apply(const BVHStaticBinary&, const BVHStaticData&) { }
+    virtual void apply(const BVHStaticTriangle&, const BVHStaticData&) { }
+    
+    const SGMatrixd& getBodyToWorld() const
+    { return _bodyToWorld; }
+    const SGVec3d& getLinearVelocity() const
+    { return _linearVelocity; }
+    const SGVec3d& getAngularVelocity() const
+    { return _angularVelocity; }
+    
+    bool empty() const
+    { return !_foundId; }
+    
+protected:
+    simgear::BVHNode::Id _id;
 
-void
-FGGroundCache::putLineLeafIntoCache(const sgdSphere *wsp, const sgdMat4 xform,
-                                    ssgLeaf *l)
+    SGMatrixd _bodyToWorld;
+
+    SGVec3d _linearVelocity;
+    SGVec3d _angularVelocity;
+    
+    bool _foundId;
+
+    double _time;
+};
+
+bool
+FGGroundCache::get_body(double t, SGMatrixd& bodyToWorld, SGVec3d& linearVel,
+                        SGVec3d& angularVel, simgear::BVHNode::Id id)
 {
-  GroundProperty gp = extractGroundProperty(l);
-
-  // Lines must have special meanings.
-  // Wires and catapults are done with lines.
-  int nl = l->getNumLines();
-  for (int i = 0; i < nl; ++i) {
-    sgdSphere sphere;
-    sphere.empty();
-    sgdVec3 ends[2];
-    short v[2];
-    l->getLine(i, v, v+1 );
-    for (int k=0; k<2; ++k) {
-      sgdSetVec3(ends[k], l->getVertex(v[k]));
-      sgdXformPnt3(ends[k], xform);
-      sphere.extend(ends[k]);
-    }
-
-    if (wsp->intersects( &sphere )) {
-      if (gp.type == FGInterface::Wire) {
-        Wire wire;
-        sgdCopyVec3(wire.ends[0], ends[0]);
-        sgdCopyVec3(wire.ends[1], ends[1]);
-        sgdCopyVec3(wire.velocity, gp.vel);
-        sgdCopyVec3(wire.rotation, gp.rot);
-        sgdSubVec3(wire.rotation_pivot, gp.pivot, cache_center);
-        wire.wire_id = gp.wire_id;
-
-        wires.push_back(wire);
-      }
-      if (gp.type == FGInterface::Catapult) {
-        Catapult cat;
-        sgdCopyVec3(cat.start, ends[0]);
-        sgdCopyVec3(cat.end, ends[1]);
-        sgdCopyVec3(cat.velocity, gp.vel);
-        sgdCopyVec3(cat.rotation, gp.rot);
-        sgdSubVec3(cat.rotation_pivot, gp.pivot, cache_center);
-
-        catapults.push_back(cat);
-      }
-    }
-  }
+    // Get the transform matrix and velocities of a moving body with id at t.
+    if (!_localBvhTree)
+        return false;
+    t += cache_time_offset;
+    BodyFinder bodyFinder(id, t);
+    _localBvhTree->accept(bodyFinder);
+    if (bodyFinder.empty())
+        return false;
+
+    bodyToWorld = bodyFinder.getBodyToWorld();
+    linearVel = bodyFinder.getLinearVelocity();
+    angularVel = bodyFinder.getAngularVelocity();
+
+    return true;
 }
 
-void
-FGGroundCache::putSurfaceLeafIntoCache(const sgdSphere *sp,
-                                       const sgdMat4 xform, bool sphIsec,
-                                       sgdVec3 down, ssgLeaf *l)
-{
-  GroundProperty gp = extractGroundProperty(l);
-
-  int nt = l->getNumTriangles();
-  for (int i = 0; i < nt; ++i) {
-    Triangle t;
-    t.sphere.empty();
-    short v[3];
-    l->getTriangle(i, &v[0], &v[1], &v[2]);
-    for (int k = 0; k < 3; ++k) {
-      sgdSetVec3(t.vertices[k], l->getVertex(v[k]));
-      sgdXformPnt3(t.vertices[k], xform);
-      t.sphere.extend(t.vertices[k]);
-    }
-
-    sgdMakePlane(t.plane, t.vertices[0], t.vertices[1], t.vertices[2]);
-    SGDfloat dot = sgdScalarProductVec3(down, t.plane);
-    if (dot > 0) {
-      if (!l->getCullFace()) {
-        // Surface points downwards, ignore for altitude computations.
-        continue;
-      } else
-        sgdScaleVec4( t.plane, -1 );
-    }
-
-    // Check if the sphere around the vehicle intersects the sphere
-    // around that triangle. If so, put that triangle into the cache.
-    if (sphIsec && sp->intersects(&t.sphere)) {
-      sgdCopyVec3(t.velocity, gp.vel);
-      sgdCopyVec3(t.rotation, gp.rot);
-      sgdSubVec3(t.rotation_pivot, gp.pivot, cache_center);
-      t.type = gp.type;
-      triangles.push_back(t);
-    }
-    
-    // In case the cache is empty, we still provide agl computations.
-    // But then we use the old way of having a fixed elevation value for
-    // the whole lifetime of this cache.
-    if ( fgdIsectSphereInfLine(t.sphere, sp->getCenter(), down) ) {
-      sgdVec3 tmp;
-      sgdSetVec3(tmp, sp->center[0], sp->center[1], sp->center[2]);
-      sgdVec3 isectpoint;
-      if ( sgdIsectInfLinePlane( isectpoint, tmp, down, t.plane ) &&
-           fgdPointInTriangle( isectpoint, t.vertices ) ) {
-        found_ground = true;
-        sgdAddVec3(isectpoint, cache_center);
-        double this_radius = sgdLengthVec3(isectpoint);
-        if (ground_radius < this_radius)
-          ground_radius = this_radius;
-      }
+class FGGroundCache::CatapultFinder : public BVHVisitor {
+public:
+    CatapultFinder(const SGSphered& sphere, const double& t) :
+        _haveLineSegment(false),
+        _sphere(sphere),
+        _time(t)
+    { }
+    
+    virtual void apply(BVHGroup& leaf)
+    {
+        if (!intersects(_sphere, leaf.getBoundingSphere()))
+            return;
+        leaf.traverse(*this);
     }
-  }
-}
+    virtual void apply(BVHTransform& transform)
+    {
+        if (!intersects(_sphere, transform.getBoundingSphere()))
+            return;
+        
+        SGSphered sphere = _sphere;
+        _sphere = transform.sphereToLocal(sphere);
+        bool haveLineSegment = _haveLineSegment;
+        _haveLineSegment = false;
+        
+        transform.traverse(*this);
+        
+        if (_haveLineSegment) {
+            _lineSegment = transform.lineSegmentToWorld(_lineSegment);
+            _linearVelocity = transform.vecToWorld(_linearVelocity);
+            _angularVelocity = transform.vecToWorld(_angularVelocity);
+        }
+        _haveLineSegment |= haveLineSegment;
+        _sphere.setCenter(sphere.getCenter());
+    }
+    virtual void apply(BVHMotionTransform& transform)
+    {
+        if (!intersects(_sphere, transform.getBoundingSphere()))
+            return;
+        
+        SGSphered sphere = _sphere;
+        _sphere = transform.sphereToLocal(sphere, _time);
+        bool haveLineSegment = _haveLineSegment;
+        _haveLineSegment = false;
+        
+        transform.traverse(*this);
+        
+        if (_haveLineSegment) {
+            SGMatrixd toWorld = transform.getToWorldTransform(_time);
+            _linearVelocity
+                += transform.getLinearVelocityAt(_lineSegment.getStart());
+            _angularVelocity += transform.getAngularVelocity();
+            _linearVelocity = toWorld.xformVec(_linearVelocity);
+            _angularVelocity = toWorld.xformVec(_angularVelocity);
+            _lineSegment = _lineSegment.transform(toWorld);
+        }
+        _haveLineSegment |= haveLineSegment;
+        _sphere.setCenter(sphere.getCenter());
+    }
+    virtual void apply(BVHLineGeometry& node)
+    {
+        if (node.getType() != BVHLineGeometry::CarrierCatapult)
+            return;
+
+        SGLineSegmentd lineSegment(node.getLineSegment());
+        if (!intersects(_sphere, lineSegment))
+            return;
+
+        _lineSegment = lineSegment;
+        double dist = distSqr(lineSegment, getSphere().getCenter());
+        _sphere.setRadius(sqrt(dist));
+        _linearVelocity = SGVec3d::zeros();
+        _angularVelocity = SGVec3d::zeros();
+        _haveLineSegment = true;
+    }
+    virtual void apply(BVHStaticGeometry& node)
+    { }
+    
+    virtual void apply(const BVHStaticBinary&, const BVHStaticData&) { }
+    virtual void apply(const BVHStaticTriangle&, const BVHStaticData&) { }
+    
+    void setSphere(const SGSphered& sphere)
+    { _sphere = sphere; }
+    const SGSphered& getSphere() const
+    { return _sphere; }
+    
+    const SGLineSegmentd& getLineSegment() const
+    { return _lineSegment; }
+    const SGVec3d& getLinearVelocity() const
+    { return _linearVelocity; }
+    const SGVec3d& getAngularVelocity() const
+    { return _angularVelocity; }
+    
+    bool getHaveLineSegment() const
+    { return _haveLineSegment; }
+    
+protected:
+    SGLineSegmentd _lineSegment;
+    SGVec3d _linearVelocity;
+    SGVec3d _angularVelocity;
+    
+    bool _haveLineSegment;
 
-inline void
-FGGroundCache::velocityTransformTriangle(double dt,
-                                         FGGroundCache::Triangle& dst,
-                                         const FGGroundCache::Triangle& src)
-{
-  sgdCopyVec3(dst.vertices[0], src.vertices[0]);
-  sgdCopyVec3(dst.vertices[1], src.vertices[1]);
-  sgdCopyVec3(dst.vertices[2], src.vertices[2]);
-
-  sgdCopyVec4(dst.plane, src.plane);
-  
-  sgdCopyVec3(dst.sphere.center, src.sphere.center);
-  dst.sphere.radius = src.sphere.radius;
-
-  sgdCopyVec3(dst.velocity, src.velocity);
-  sgdCopyVec3(dst.rotation, src.rotation);
-  sgdCopyVec3(dst.rotation_pivot, src.rotation_pivot);
-
-  dst.type = src.type;
-
-  if (dt*sgdLengthSquaredVec3(src.velocity) != 0) {
-    sgdVec3 pivotoff, vel;
-    for (int i = 0; i < 3; ++i) {
-      sgdSubVec3(pivotoff, src.vertices[i], src.rotation_pivot);
-      sgdVectorProductVec3(vel, src.rotation, pivotoff);
-      sgdAddVec3(vel, src.velocity);
-      sgdAddScaledVec3(dst.vertices[i], vel, dt);
-    }
-    
-    // Transform the plane equation
-    sgdSubVec3(pivotoff, dst.plane, src.rotation_pivot);
-    sgdVectorProductVec3(vel, src.rotation, pivotoff);
-    sgdAddVec3(vel, src.velocity);
-    dst.plane[3] += dt*sgdScalarProductVec3(dst.plane, vel);
-
-    sgdAddScaledVec3(dst.sphere.center, src.velocity, dt);
-  }
-}
+    SGSphered _sphere;
+    double _time;
+};
 
-void
-FGGroundCache::cache_fill(ssgBranch *branch, sgdMat4 xform,
-                          sgdSphere* sp, sgdVec3 down, sgdSphere* wsp)
+double
+FGGroundCache::get_cat(double t, const SGVec3d& pt,
+                       SGVec3d end[2], SGVec3d vel[2])
 {
-  // Travel through all kids.
-  ssgEntity *e;
-  for ( e = branch->getKid(0); e != NULL ; e = branch->getNextKid() ) {
-    if ( !(e->getTraversalMask() & SSGTRAV_HOT) )
-      continue;
-    if ( e->getBSphere()->isEmpty() )
-      continue;
-    
-    // We need to check further if either the sphere around the branch
-    // intersects the sphere around the aircraft or the line downwards from
-    // the aircraft intersects the branchs sphere.
-    sgdSphere esphere;
-    sgdSetVec3(esphere.center, e->getBSphere()->center);
-    esphere.radius = e->getBSphere()->radius;
-    esphere.orthoXform(xform);
-    bool wspIsec = wsp->intersects(&esphere);
-    bool downIsec = fgdIsectSphereInfLine(esphere, sp->getCenter(), down);
-    if (!wspIsec && !downIsec)
-      continue;
-
-    // For branches collect up the transforms to reach that branch and
-    // call cache_fill recursively.
-    if ( e->isAKindOf( ssgTypeBranch() ) ) {
-      ssgBranch *b = (ssgBranch *)e;
-      if ( b->isAKindOf( ssgTypeTransform() ) ) {
-        // Collect up the transfors required to reach that part of
-        // the branch.
-        sgMat4 xform2;
-        sgMakeIdentMat4( xform2 );
-        ssgTransform *t = (ssgTransform*)b;
-        t->getTransform( xform2 );
-        sgdMat4 xform3;
-        fgMultMat4(xform3, xform, xform2);
-        cache_fill( b, xform3, sp, down, wsp );
-      } else
-        cache_fill( b, xform, sp, down, wsp );
-    }
-   
-    // For leafs, check each triangle for intersection.
-    // This will minimize the number of vertices/triangles in the cache.
-    else if (e->isAKindOf(ssgTypeLeaf())) {
-      // Since we reach that leaf if we have an intersection with the
-      // most propably bigger wire/catapult cache sphere, we need to check
-      // that here, if the smaller cache for the surface has a chance for hits.
-      // Also, if the spheres do not intersect compute a croase agl value
-      // by following the line downwards originating at the aircraft.
-      bool spIsec = sp->intersects(&esphere);
-      putSurfaceLeafIntoCache(sp, xform, spIsec, down, (ssgLeaf *)e);
-
-      // If we are here, we need to put all special hardware here into
-      // the cache.
-      if (wspIsec)
-        putLineLeafIntoCache(wsp, xform, (ssgLeaf *)e);
-    }
-  }
+    double maxDistance = 1000;
+
+    // Get the wire in question
+    t += cache_time_offset;
+    CatapultFinder catapultFinder(SGSphered(pt, maxDistance), t);
+    if (_localBvhTree)
+        _localBvhTree->accept(catapultFinder);
+    
+    if (!catapultFinder.getHaveLineSegment())
+        return maxDistance;
+
+    // prepare the returns
+    end[0] = catapultFinder.getLineSegment().getStart();
+    end[1] = catapultFinder.getLineSegment().getEnd();
+
+    // The linear velocity is the one at the start of the line segment ...
+    vel[0] = catapultFinder.getLinearVelocity();
+    // ... so the end point has the additional cross product.
+    vel[1] = catapultFinder.getLinearVelocity();
+    vel[1] += cross(catapultFinder.getAngularVelocity(),
+                    catapultFinder.getLineSegment().getDirection());
+
+    // Return the distance to the cat
+    return sqrt(distSqr(catapultFinder.getLineSegment(), pt));
 }
 
 bool
-FGGroundCache::prepare_ground_cache(double ref_time, const double pt[3],
-                                    double rad)
+FGGroundCache::get_agl(double t, const SGVec3d& pt, SGVec3d& contact,
+                       SGVec3d& normal, SGVec3d& linearVel, SGVec3d& angularVel,
+                       simgear::BVHNode::Id& id, const SGMaterial*& material)
 {
-  // Empty cache.
-  ground_radius = 0.0;
-  found_ground = false;
-  triangles.resize(0);
-  catapults.resize(0);
-  wires.resize(0);
-
-  // Store the parameters we used to build up that cache.
-  sgdCopyVec3(reference_wgs84_point, pt);
-  reference_vehicle_radius = rad;
-  // Store the time reference used to compute movements of moving triangles.
-  cache_ref_time = ref_time;
-
-  // Decide where we put the scenery center.
-  Point3D old_cntr = globals->get_scenery()->get_center();
-  Point3D cntr(pt[0], pt[1], pt[2]);
-  // Only move the cache center if it is unaccaptable far away.
-  if (40*40 < old_cntr.distance3Dsquared(cntr))
-    globals->get_scenery()->set_center(cntr);
-  else
-    cntr = old_cntr;
-
-  // The center of the cache.
-  sgdSetVec3(cache_center, cntr[0], cntr[1], cntr[2]);
-  
-  sgdVec3 ptoff;
-  sgdSubVec3(ptoff, pt, cache_center);
-  // Prepare sphere around the aircraft.
-  sgdSphere acSphere;
-  acSphere.setRadius(rad);
-  acSphere.setCenter(ptoff);
-
-  // Prepare bigger sphere around the aircraft.
-  // This one is required for reliably finding wires we have caught but
-  // have already left the hopefully smaller sphere for the ground reactions.
-  const double max_wire_dist = 300.0;
-  sgdSphere wireSphere;
-  wireSphere.setRadius(max_wire_dist < rad ? rad : max_wire_dist);
-  wireSphere.setCenter(ptoff);
-
-  // Down vector. Is used for croase agl computations when we are far enough
-  // from ground that we have an empty cache.
-  sgdVec3 down;
-  sgdSetVec3(down, -pt[0], -pt[1], -pt[2]);
-  sgdNormalizeVec3(down);
-
-  // We collaps all transforms we need to reach a particular leaf.
-  // The leafs itself will be then transformed later.
-  // So our cache is just flat.
-  // For leafs which are moving (carriers surface, etc ...)
-  // we will later store a speed in the GroundType class. We can then apply
-  // some translations to that nodes according to the time which has passed
-  // compared to that snapshot.
-  sgdMat4 xform;
-  sgdMakeIdentMat4( xform );
-
-
-  // Walk the scene graph and extract solid ground triangles and carrier data.
-  ssgBranch *terrain = globals->get_scenery()->get_scene_graph();
-  cache_fill(terrain, xform, &acSphere, down, &wireSphere);
-
-  // some stats
-  SG_LOG(SG_FLIGHT,SG_DEBUG, "prepare_ground_cache(): ac radius = " << rad
-         << ", # triangles = " << triangles.size()
-         << ", # wires = " << wires.size()
-         << ", # catapults = " << catapults.size()
-         << ", ground_radius = " << ground_radius );
-
-  // If the ground radius is still below 5e6 meters, then we do not yet have
-  // any scenery.
-  found_ground = found_ground && 5e6 < ground_radius;
-  if (!found_ground)
-    SG_LOG(SG_FLIGHT, SG_WARN, "prepare_ground_cache(): trying to build cache "
-           "without any scenery below the aircraft" );
-
-  if (cntr != old_cntr)
-    globals->get_scenery()->set_center(old_cntr);
-
-  return found_ground;
+#ifdef GROUNDCACHE_DEBUG
+    SGTimeStamp t0 = SGTimeStamp::now();
+#endif
+
+    // Just set up a ground intersection query for the given point
+    SGLineSegmentd line(pt, pt + 10*reference_vehicle_radius*down);
+    t += cache_time_offset;
+    simgear::BVHLineSegmentVisitor lineSegmentVisitor(line, t);
+    if (_localBvhTree)
+        _localBvhTree->accept(lineSegmentVisitor);
+
+#ifdef GROUNDCACHE_DEBUG
+    t0 = SGTimeStamp::now() - t0;
+    _lookupTime += t0;
+    _lookupCount++;
+#endif
+
+    if (!lineSegmentVisitor.empty()) {
+        // Have an intersection
+        contact = lineSegmentVisitor.getPoint();
+        normal = lineSegmentVisitor.getNormal();
+        if (0 < dot(normal, down))
+            normal = -normal;
+        linearVel = lineSegmentVisitor.getLinearVelocity();
+        angularVel = lineSegmentVisitor.getAngularVelocity();
+        material = lineSegmentVisitor.getMaterial();
+        id = lineSegmentVisitor.getId();
+
+        return true;
+    } else {
+        // Whenever we did not have a ground triangle for the requested point,
+        // take the ground level we found during the current cache build.
+        // This is as good as what we had before for agl.
+        SGGeod geodPt = SGGeod::fromCart(pt);
+        geodPt.setElevationM(_altitude);
+        contact = SGVec3d::fromGeod(geodPt);
+        normal = -down;
+        linearVel = SGVec3d(0, 0, 0);
+        angularVel = SGVec3d(0, 0, 0);
+        material = _material;
+        id = 0;
+
+        return found_ground;
+    }
 }
 
+
 bool
-FGGroundCache::is_valid(double *ref_time, double pt[3], double *rad)
+FGGroundCache::get_nearest(double t, const SGVec3d& pt, double maxDist,
+                           SGVec3d& contact, SGVec3d& linearVel,
+                           SGVec3d& angularVel, simgear::BVHNode::Id& id,
+                           const SGMaterial*& material)
 {
-  sgdCopyVec3(pt, reference_wgs84_point);
-  *rad = reference_vehicle_radius;
-  *ref_time = cache_ref_time;
-  return found_ground;
+    if (!_localBvhTree)
+        return false;
+
+#ifdef GROUNDCACHE_DEBUG
+    SGTimeStamp t0 = SGTimeStamp::now();
+#endif
+
+    // Just set up a ground intersection query for the given point
+    SGSphered sphere(pt, maxDist);
+    t += cache_time_offset;
+    simgear::BVHNearestPointVisitor nearestPointVisitor(sphere, t);
+    _localBvhTree->accept(nearestPointVisitor);
+
+#ifdef GROUNDCACHE_DEBUG
+    t0 = SGTimeStamp::now() - t0;
+    _lookupTime += t0;
+    _lookupCount++;
+#endif
+
+    if (nearestPointVisitor.empty())
+        return false;
+
+    // Have geometry in the range of maxDist
+    contact = nearestPointVisitor.getPoint();
+    linearVel = nearestPointVisitor.getLinearVelocity();
+    angularVel = nearestPointVisitor.getAngularVelocity();
+    material = nearestPointVisitor.getMaterial();
+    id = nearestPointVisitor.getId();
+    
+    return true;
 }
 
-double
-FGGroundCache::get_cat(double t, const double dpt[3],
-                       double end[2][3], double vel[2][3])
-{
-  // start with a distance of 1e10 meters...
-  double dist = 1e10;
-
-  // Time difference to the reference time.
-  t -= cache_ref_time;
-
-  size_t sz = catapults.size();
-  for (size_t i = 0; i < sz; ++i) {
-    sgdVec3 pivotoff, rvel[2];
-    sgdLineSegment3 ls;
-    sgdCopyVec3(ls.a, catapults[i].start);
-    sgdCopyVec3(ls.b, catapults[i].end);
-
-    sgdSubVec3(pivotoff, ls.a, catapults[i].rotation_pivot);
-    sgdVectorProductVec3(rvel[0], catapults[i].rotation, pivotoff);
-    sgdAddVec3(rvel[0], catapults[i].velocity);
-    sgdSubVec3(pivotoff, ls.b, catapults[i].rotation_pivot);
-    sgdVectorProductVec3(rvel[1], catapults[i].rotation, pivotoff);
-    sgdAddVec3(rvel[1], catapults[i].velocity);
-
-    sgdAddVec3(ls.a, cache_center);
-    sgdAddVec3(ls.b, cache_center);
-
-    sgdAddScaledVec3(ls.a, rvel[0], t);
-    sgdAddScaledVec3(ls.b, rvel[1], t);
-    
-    double this_dist = sgdDistSquaredToLineSegmentVec3( ls, dpt );
-    if (this_dist < dist) {
-      SG_LOG(SG_FLIGHT,SG_INFO, "Found catapult "
-             << this_dist << " meters away");
-      dist = this_dist;
-        
-      // The carrier code takes care of that ordering.
-      sgdCopyVec3( end[0], ls.a );
-      sgdCopyVec3( end[1], ls.b );
-      sgdCopyVec3( vel[0], rvel[0] );
-      sgdCopyVec3( vel[1], rvel[1] );
+
+class FGGroundCache::WireIntersector : public BVHVisitor {
+public:
+    WireIntersector(const SGVec3d pt[4], const double& t) :
+        _linearVelocity(SGVec3d::zeros()),
+        _angularVelocity(SGVec3d::zeros()),
+        _wire(0),
+        _time(t)
+    {
+        // Build the two triangles spanning the area where the hook has moved
+        // during the past step.
+        _triangles[0].set(pt[0], pt[1], pt[2]);
+        _triangles[1].set(pt[0], pt[2], pt[3]);
     }
-  }
 
-  // At the end take the root, we only computed squared distances ...
-  return sqrt(dist);
-}
+    virtual void apply(BVHGroup& leaf)
+    {
+        if (!_intersects(leaf.getBoundingSphere()))
+            return;
 
-bool
-FGGroundCache::get_agl(double t, const double dpt[3], double max_altoff,
-                       double contact[3], double normal[3], double vel[3],
-                       int *type, double *loadCapacity,
-                       double *frictionFactor, double *agl)
-{
-  bool ret = false;
-
-  *type = FGInterface::Unknown;
-//   *agl = 0.0;
-  *loadCapacity = DBL_MAX;
-  *frictionFactor = 1.0;
-  sgdSetVec3( vel, 0.0, 0.0, 0.0 );
-  sgdSetVec3( contact, 0.0, 0.0, 0.0 );
-  sgdSetVec3( normal, 0.0, 0.0, 0.0 );
-
-  // Time difference to th reference time.
-  t -= cache_ref_time;
-
-  // The double valued point we start to search for intersection.
-  sgdVec3 pt;
-  sgdSubVec3( pt, dpt, cache_center );
-
-  // The search direction
-  sgdVec3 dir;
-  sgdSetVec3( dir, -dpt[0], -dpt[1], -dpt[2] );
-  sgdNormaliseVec3( dir );
-
-  // Initialize to something sensible
-  double current_radius = 0.0;
-
-  size_t sz = triangles.size();
-  for (size_t i = 0; i < sz; ++i) {
-    Triangle triangle;
-    velocityTransformTriangle(t, triangle, triangles[i]);
-    if (!fgdIsectSphereInfLine(triangle.sphere, pt, dir))
-      continue;
-
-    // Check for intersection.
-    sgdVec3 isecpoint;
-    if ( sgdIsectInfLinePlane( isecpoint, pt, dir, triangle.plane ) &&
-         sgdPointInTriangle( isecpoint, triangle.vertices ) ) {
-      // Transform to the wgs system
-      sgdAddVec3( isecpoint, cache_center );
-      // compute the radius, good enough approximation to take the geocentric radius
-      SGDfloat radius = sgdLengthSquaredVec3(isecpoint);
-      if (current_radius < radius) {
-        // Compute the vector from pt to the intersection point ...
-        sgdVec3 off;
-        sgdSubVec3(off, pt, isecpoint);
-        // ... and check if it is too high or not
-        if (-max_altoff < sgdScalarProductVec3( off, dir )) {
-          current_radius = radius;
-          ret = true;
-          // Save the new potential intersection point.
-          sgdCopyVec3( contact, isecpoint );
-          // The first three values in the vector are the plane normal.
-          sgdCopyVec3( normal, triangle.plane );
-          // The velocity wrt earth.
-          sgdVec3 pivotoff;
-          sgdSubVec3(pivotoff, pt, triangle.rotation_pivot);
-          sgdVectorProductVec3(vel, triangle.rotation, pivotoff);
-          sgdAddVec3(vel, triangle.velocity);
-          // Save the ground type.
-          *type = triangle.type;
-          // FIXME: figure out how to get that sign ...
-//           *agl = sqrt(sqdist);
-          *agl = sgdLengthVec3( dpt ) - sgdLengthVec3( contact );
-//           *loadCapacity = DBL_MAX;
-//           *frictionFactor = 1.0;
+        leaf.traverse(*this);
+    }
+    virtual void apply(BVHTransform& transform)
+    {
+        if (!_intersects(transform.getBoundingSphere()))
+            return;
+        
+        SGTriangled triangles[2] = { _triangles[0], _triangles[1] };
+        _triangles[0] = triangles[0].transform(transform.getToLocalTransform());
+        _triangles[1] = triangles[1].transform(transform.getToLocalTransform());
+        
+        transform.traverse(*this);
+        
+        if (_wire) {
+            _lineSegment = transform.lineSegmentToWorld(_lineSegment);
+            _linearVelocity = transform.vecToWorld(_linearVelocity);
+            _angularVelocity = transform.vecToWorld(_angularVelocity);
         }
-      }
+        _triangles[0] = triangles[0];
+        _triangles[1] = triangles[1];
     }
-  }
+    virtual void apply(BVHMotionTransform& transform)
+    {
+        if (!_intersects(transform.getBoundingSphere()))
+            return;
+        
+        SGMatrixd toLocal = transform.getToLocalTransform(_time);
 
-  if (ret)
-    return true;
+        SGTriangled triangles[2] = { _triangles[0], _triangles[1] };
+        _triangles[0] = triangles[0].transform(toLocal);
+        _triangles[1] = triangles[1].transform(toLocal);
+        
+        transform.traverse(*this);
+        
+        if (_wire) {
+            SGMatrixd toWorld = transform.getToWorldTransform(_time);
+            _linearVelocity
+                += transform.getLinearVelocityAt(_lineSegment.getStart());
+            _angularVelocity += transform.getAngularVelocity();
+            _linearVelocity = toWorld.xformVec(_linearVelocity);
+            _angularVelocity = toWorld.xformVec(_angularVelocity);
+            _lineSegment = _lineSegment.transform(toWorld);
+        }
+        _triangles[0] = triangles[0];
+        _triangles[1] = triangles[1];
+    }
+    virtual void apply(BVHLineGeometry& node)
+    {
+        if (node.getType() != BVHLineGeometry::CarrierWire)
+            return;
+        SGLineSegmentd lineSegment(node.getLineSegment());
+        if (!_intersects(lineSegment))
+            return;
+
+        _lineSegment = lineSegment;
+        _linearVelocity = SGVec3d::zeros();
+        _angularVelocity = SGVec3d::zeros();
+        _wire = &node;
+    }
+    virtual void apply(BVHStaticGeometry& node)
+    { }
+    
+    virtual void apply(const BVHStaticBinary&, const BVHStaticData&) { }
+    virtual void apply(const BVHStaticTriangle&, const BVHStaticData&) { }
+
+    bool _intersects(const SGSphered& sphere) const
+    {
+        if (_wire)
+            return false;
+        if (intersects(_triangles[0], sphere))
+            return true;
+        if (intersects(_triangles[1], sphere))
+            return true;
+        return false;
+    }
+    bool _intersects(const SGLineSegmentd& lineSegment) const
+    {
+        if (_wire)
+            return false;
+        if (intersects(_triangles[0], lineSegment))
+            return true;
+        if (intersects(_triangles[1], lineSegment))
+            return true;
+        return false;
+    }
+    
+    const SGLineSegmentd& getLineSegment() const
+    { return _lineSegment; }
+    const SGVec3d& getLinearVelocity() const
+    { return _linearVelocity; }
+    const SGVec3d& getAngularVelocity() const
+    { return _angularVelocity; }
+    
+    const BVHLineGeometry* getWire() const
+    { return _wire; }
+    
+private:
+    SGLineSegmentd _lineSegment;
+    SGVec3d _linearVelocity;
+    SGVec3d _angularVelocity;
+    const BVHLineGeometry* _wire;
 
-  // Whenever we did not have a ground triangle for the requested point,
-  // take the ground level we found during the current cache build.
-  // This is as good as what we had before for agl.
-  double r = sgdLengthVec3( dpt );
-  sgdCopyVec3( contact, dpt );
-  sgdScaleVec3( contact, ground_radius/r );
-  sgdCopyVec3( normal, dpt );
-  sgdNormaliseVec3( normal );
-  sgdSetVec3( vel, 0.0, 0.0, 0.0 );
-  
-  // The altitude is the distance of the requested point from the
-  // contact point.
-  *agl = sgdLengthVec3( dpt ) - sgdLengthVec3( contact );
-  *type = FGInterface::Unknown;
-  *loadCapacity = DBL_MAX;
-  *frictionFactor = 1.0;
-
-  return ret;
-}
+    SGTriangled _triangles[2];
+    double _time;
+};
 
-bool FGGroundCache::caught_wire(double t, const double pt[4][3])
+bool FGGroundCache::caught_wire(double t, const SGVec3d pt[4])
 {
-  size_t sz = wires.size();
-  if (sz == 0)
-    return false;
-
-  // Time difference to the reference time.
-  t -= cache_ref_time;
-
-  // Build the two triangles spanning the area where the hook has moved
-  // during the past step.
-  sgdVec4 plane[2];
-  sgdVec3 tri[2][3];
-  sgdMakePlane( plane[0], pt[0], pt[1], pt[2] );
-  sgdCopyVec3( tri[0][0], pt[0] );
-  sgdCopyVec3( tri[0][1], pt[1] );
-  sgdCopyVec3( tri[0][2], pt[2] );
-  sgdMakePlane( plane[1], pt[0], pt[2], pt[3] );
-  sgdCopyVec3( tri[1][0], pt[0] );
-  sgdCopyVec3( tri[1][1], pt[2] );
-  sgdCopyVec3( tri[1][2], pt[3] );
-
-  // Intersect the wire lines with each of these triangles.
-  // You have cautght a wire if they intersect.
-  for (size_t i = 0; i < sz; ++i) {
-    sgdVec3 le[2];
-    for (int k = 0; k < 2; ++k) {
-      sgdVec3 pivotoff, vel;
-      sgdCopyVec3(le[k], wires[i].ends[k]);
-      sgdSubVec3(pivotoff, le[k], wires[i].rotation_pivot);
-      sgdVectorProductVec3(vel, wires[i].rotation, pivotoff);
-      sgdAddVec3(vel, wires[i].velocity);
-      sgdAddScaledVec3(le[k], vel, t);
-      sgdAddVec3(le[k], cache_center);
-    }
-    
-    for (int k=0; k<2; ++k) {
-      sgdVec3 isecpoint;
-      double isecval = sgdIsectLinesegPlane(isecpoint, le[0], le[1], plane[k]);
-      if ( 0.0 <= isecval && isecval <= 1.0 &&
-           sgdPointInTriangle( isecpoint, tri[k] ) ) {
-        SG_LOG(SG_FLIGHT,SG_INFO, "Caught wire");
-        // Store the wire id.
-        wire_id = wires[i].wire_id;
-        return true;
-      }
+    // Get the wire in question
+    t += cache_time_offset;
+    WireIntersector wireIntersector(pt, t);
+    if (_localBvhTree)
+        _localBvhTree->accept(wireIntersector);
+    
+    _wire = wireIntersector.getWire();
+    return _wire;
+}
+
+class FGGroundCache::WireFinder : public BVHVisitor {
+public:
+    WireFinder(const BVHLineGeometry* wire, const double& t) :
+        _wire(wire),
+        _time(t),
+        _lineSegment(SGVec3d::zeros(), SGVec3d::zeros()),
+        _linearVelocity(SGVec3d::zeros()),
+        _angularVelocity(SGVec3d::zeros()),
+        _haveLineSegment(false)
+    { }
+
+    virtual void apply(BVHGroup& leaf)
+    {
+        if (_haveLineSegment)
+            return;
+        leaf.traverse(*this);
     }
-  }
+    virtual void apply(BVHTransform& transform)
+    {
+        if (_haveLineSegment)
+            return;
 
-  return false;
-}
+        transform.traverse(*this);
+        
+        if (_haveLineSegment) {
+            _linearVelocity = transform.vecToWorld(_linearVelocity);
+            _angularVelocity = transform.vecToWorld(_angularVelocity);
+            _lineSegment = transform.lineSegmentToWorld(_lineSegment);
+        }
+    }
+    virtual void apply(BVHMotionTransform& transform)
+    {
+        if (_haveLineSegment)
+            return;
+
+        transform.traverse(*this);
+        
+        if (_haveLineSegment) {
+            SGMatrixd toWorld = transform.getToWorldTransform(_time);
+            _linearVelocity
+                += transform.getLinearVelocityAt(_lineSegment.getStart());
+            _angularVelocity += transform.getAngularVelocity();
+            _linearVelocity = toWorld.xformVec(_linearVelocity);
+            _angularVelocity = toWorld.xformVec(_angularVelocity);
+            _lineSegment = _lineSegment.transform(toWorld);
+        }
+    }
+    virtual void apply(BVHLineGeometry& node)
+    {
+        if (_haveLineSegment)
+            return;
+        if (_wire != &node)
+            return;
+        if (node.getType() != BVHLineGeometry::CarrierWire)
+            return;
+        _lineSegment = SGLineSegmentd(node.getLineSegment());
+        _linearVelocity = SGVec3d::zeros();
+        _angularVelocity = SGVec3d::zeros();
+        _haveLineSegment = true;
+    }
+    virtual void apply(BVHStaticGeometry&) { }
+    
+    virtual void apply(const BVHStaticBinary&, const BVHStaticData&) { }
+    virtual void apply(const BVHStaticTriangle&, const BVHStaticData&) { }
+
+    const SGLineSegmentd& getLineSegment() const
+    { return _lineSegment; }
+    
+    bool getHaveLineSegment() const
+    { return _haveLineSegment; }
+
+    const SGVec3d& getLinearVelocity() const
+    { return _linearVelocity; }
+    const SGVec3d& getAngularVelocity() const
+    { return _angularVelocity; }
 
-bool FGGroundCache::get_wire_ends(double t, double end[2][3], double vel[2][3])
+private:
+    const BVHLineGeometry* _wire;
+    double _time;
+
+    SGLineSegmentd _lineSegment;
+    SGVec3d _linearVelocity;
+    SGVec3d _angularVelocity;
+
+    bool _haveLineSegment;
+};
+
+bool FGGroundCache::get_wire_ends(double t, SGVec3d end[2], SGVec3d vel[2])
 {
-  // Fast return if we do not have an active wire.
-  if (wire_id < 0)
-    return false;
-
-  // Time difference to the reference time.
-  t -= cache_ref_time;
-
-  // Search for the wire with the matching wire id.
-  size_t sz = wires.size();
-  for (size_t i = 0; i < sz; ++i) {
-    if (wires[i].wire_id == wire_id) {
-      for (size_t k = 0; k < 2; ++k) {
-        sgdVec3 pivotoff;
-        sgdCopyVec3(end[k], wires[i].ends[k]);
-        sgdSubVec3(pivotoff, end[k], wires[i].rotation_pivot);
-        sgdVectorProductVec3(vel[k], wires[i].rotation, pivotoff);
-        sgdAddVec3(vel[k], wires[i].velocity);
-        sgdAddScaledVec3(end[k], vel[k], t);
-        sgdAddVec3(end[k], cache_center);
-      }
-      return true;
-    }
-  }
-
-  return false;
+    // Fast return if we do not have an active wire.
+    if (!_wire)
+        return false;
+
+    // Get the wire in question
+    t += cache_time_offset;
+    WireFinder wireFinder(_wire, t);
+    if (_localBvhTree)
+        _localBvhTree->accept(wireFinder);
+    
+    if (!wireFinder.getHaveLineSegment())
+        return false;
+
+    // prepare the returns
+    end[0] = wireFinder.getLineSegment().getStart();
+    end[1] = wireFinder.getLineSegment().getEnd();
+
+    // The linear velocity is the one at the start of the line segment ...
+    vel[0] = wireFinder.getLinearVelocity();
+    // ... so the end point has the additional cross product.
+    vel[1] = wireFinder.getLinearVelocity();
+    vel[1] += cross(wireFinder.getAngularVelocity(),
+                    wireFinder.getLineSegment().getDirection());
+
+    return true;
 }
 
 void FGGroundCache::release_wire(void)
 {
-  wire_id = -1;
+    _wire = 0;
 }