]> git.mxchange.org Git - flightgear.git/blobdiff - src/FDM/groundcache.cxx
Remove the StaticLeaf visitor methods.
[flightgear.git] / src / FDM / groundcache.cxx
index 575cd8435343e113d3a58fdc8cd733ede906c982..6818577f0751a789f1ed40f3f5b987f03b833de1 100644 (file)
 #  include "config.h"
 #endif
 
-#include <float.h>
+#include <utility>
 
-#include <osg/CullFace>
 #include <osg/Drawable>
 #include <osg/Geode>
 #include <osg/Geometry>
-#include <osg/TriangleFunctor>
+#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/scene/material/mat.hxx>
-#include <simgear/scene/material/matlib.hxx>
 #include <simgear/scene/util/SGNodeMasks.hxx>
+#include <simgear/scene/util/SGSceneUserData.hxx>
+#include <simgear/scene/model/placementtrans.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 <Main/globals.hxx>
 #include <Scenery/scenery.hxx>
 #include <Scenery/tilemgr.hxx>
-#include <AIModel/AICarrier.hxx>
 
 #include "flight.hxx"
 #include "groundcache.hxx"
 
-/// Ok, variant that uses a infinite line istead of the ray.
-/// also not that this only works if the ray direction is normalized.
-static inline bool
-intersectsInf(const SGRayd& ray, const SGSphered& sphere)
+using namespace simgear;
+
+static FGInterface::GroundType
+materialToGroundType(const SGMaterial* material)
 {
-  SGVec3d r = sphere.getCenter() - ray.getOrigin();
-  double projectedDistance = dot(r, ray.getDirection());
-  double dist = dot(r, r) - projectedDistance * projectedDistance;
-  return dist < sphere.getRadius2();
+    if (!material)
+        return FGInterface::Solid;
+    if (material->get_solid())
+        return FGInterface::Solid;
+    return FGInterface::Water;
 }
 
-template<typename T>
-class SGExtendedTriangleFunctor : public osg::TriangleFunctor<T> {
+class FGGroundCache::CacheFill : public osg::NodeVisitor {
 public:
-  // Ok, to be complete we should also implement the indexed variants
-  // For now this one appears to be enough ...
-  void drawArrays(GLenum mode, GLint first, GLsizei count)
-  {
-    if (_vertexArrayPtr==0 || count==0) return;
-
-    const osg::Vec3* vlast;
-    const osg::Vec3* vptr;
-    switch(mode) {
-    case(GL_LINES):
-      vlast = &_vertexArrayPtr[first+count];
-      for(vptr=&_vertexArrayPtr[first];vptr<vlast;vptr+=2)
-        this->operator()(*(vptr),*(vptr+1),_treatVertexDataAsTemporary);
-      break;
-    case(GL_LINE_STRIP):
-      vlast = &_vertexArrayPtr[first+count-1];
-      for(vptr=&_vertexArrayPtr[first];vptr<vlast;++vptr)
-        this->operator()(*(vptr),*(vptr+1),_treatVertexDataAsTemporary);
-      break;
-    case(GL_LINE_LOOP):
-      vlast = &_vertexArrayPtr[first+count-1];
-      for(vptr=&_vertexArrayPtr[first];vptr<vlast;++vptr)
-        this->operator()(*(vptr),*(vptr+1),_treatVertexDataAsTemporary);
-      this->operator()(_vertexArrayPtr[first+count-1],
-                       _vertexArrayPtr[first],_treatVertexDataAsTemporary);
-      break;
-    default:
-      osg::TriangleFunctor<T>::drawArrays(mode, first, count);
-      break;
+    CacheFill(const SGVec3d& center, const double& radius,
+              const double& startTime, const double& endTime) :
+        osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ACTIVE_CHILDREN),
+        _center(center),
+        _radius(radius),
+        _startTime(startTime),
+        _endTime(endTime)
+    {
+        setTraversalMask(SG_NODEMASK_TERRAIN_BIT);
     }
-  }
-protected:
-  using osg::TriangleFunctor<T>::_vertexArrayPtr;
-  using osg::TriangleFunctor<T>::_treatVertexDataAsTemporary;
-};
+    virtual void apply(osg::Node& node)
+    {
+        if (!testBoundingSphere(node.getBound()))
+            return;
 
-class GroundCacheFillVisitor : public osg::NodeVisitor {
-public:
-  
-  /// class to just redirect triangles to the GroundCacheFillVisitor
-  class GroundCacheFill {
-  public:
-    void setGroundCacheFillVisitor(GroundCacheFillVisitor* gcfv)
-    { mGroundCacheFillVisitor = gcfv; }
+        addBoundingVolume(node);
+    }
     
-    void operator () (const osg::Vec3& v1, const osg::Vec3& v2,
-                      const osg::Vec3& v3, bool)
-    { mGroundCacheFillVisitor->addTriangle(v1, v2, v3); }
+    virtual void apply(osg::Group& group)
+    {
+        if (!testBoundingSphere(group.getBound()))
+            return;
 
-    void operator () (const osg::Vec3& v1, const osg::Vec3& v2, bool)
-    { mGroundCacheFillVisitor->addLine(v1, v2); }
+        simgear::BVHSubTreeCollector::NodeList parentNodeList;
+        mSubTreeCollector.pushNodeList(parentNodeList);
+        
+        traverse(group);
+        addBoundingVolume(group);
+        
+        mSubTreeCollector.popNodeList(parentNodeList);
+    }
     
-  private:
-    GroundCacheFillVisitor* mGroundCacheFillVisitor;
-  };
-
-
-  GroundCacheFillVisitor(FGGroundCache* groundCache,
-                         const SGVec3d& down, 
-                         const SGVec3d& cacheReference,
-                         double cacheRadius,
-                         double wireCacheRadius) :
-    osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ACTIVE_CHILDREN),
-    mGroundCache(groundCache)
-  {
-    setTraversalMask(SG_NODEMASK_TERRAIN_BIT);
-    mDown = down;
-    mLocalDown = down;
-    sphIsec = true;
-    mBackfaceCulling = false;
-    mCacheReference = cacheReference;
-    mLocalCacheReference = cacheReference;
-    mCacheRadius = cacheRadius;
-    mWireCacheRadius = wireCacheRadius;
-
-    mTriangleFunctor.setGroundCacheFillVisitor(this);
-
-    mGroundProperty.wire_id = -1;
-    mGroundProperty.vel = SGVec3d(0, 0, 0);
-    mGroundProperty.rot = SGVec3d(0, 0, 0);
-    mGroundProperty.pivot = SGVec3d(0, 0, 0);
-  }
-
-  void updateCullMode(osg::StateSet* stateSet)
-  {
-    if (!stateSet)
-      return;
-
-    osg::StateAttribute* stateAttribute;
-    stateAttribute = stateSet->getAttribute(osg::StateAttribute::CULLFACE);
-    if (!stateAttribute)
-      return;
-    osg::CullFace* cullFace = static_cast<osg::CullFace*>(stateAttribute);
-    mBackfaceCulling = cullFace->getMode() == osg::CullFace::BACK;
-  }
-
-  bool enterBoundingSphere(const osg::BoundingSphere& bs)
-  {
-    if (!bs.valid())
-      return false;
-
-    SGVec3d cntr(osg::Vec3d(bs.center())*mLocalToGlobal);
-    double rc = bs.radius() + mCacheRadius;
-    // Ok, this node might intersect the cache. Visit it in depth.
-    double centerDist2 = distSqr(mCacheReference, cntr);
-    if (centerDist2 < rc*rc) {
-      sphIsec = true;
-    } else {
-      // Check if the down direction touches the bounding sphere of the node
-      // if so, do at least croase agl computations.
-      // Ther other thing is that we must check if we are in range of
-      // cats or wires
-      double rw = bs.radius() + mWireCacheRadius;
-      if (rw*rw < centerDist2 &&
-          !intersectsInf(SGRayd(mCacheReference, mDown),
-                         SGSphered(cntr, bs.radius())))
-        return false;
-      sphIsec = false;
+    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);
+        // ... no velocity of there is only zero velocity
+        if (velocity && velocity->linear == SGVec3d::zeros() &&
+            velocity->angular == SGVec3d::zeros())
+            velocity = 0;
+        
+        SGVec3d center = _center;
+        _center = SGVec3d(inverseMatrix.preMult(_center.osg()));
+        double radius = _radius;
+        if (velocity)
+            _radius += (_endTime - _startTime)*norm(velocity->linear);
+        
+        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(_startTime);
+                bvhTransform->setEndTime(_endTime);
+
+                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);
+        }
+        _center = center;
+        _radius = radius;
     }
 
-    return true;
-  }
-
-  bool enterNode(osg::Node& node)
-  {
-    if (!enterBoundingSphere(node.getBound()))
-      return false;
-
-    updateCullMode(node.getStateSet());
-
-    FGGroundCache::GroundProperty& gp = mGroundProperty;
-    // get some material information for use in the gear model
-    gp.type = FGInterface::Unknown;
-    osg::Referenced* base = node.getUserData();
-    if (!base)
-      return true;
-    FGAICarrierHardware *ud =
-      dynamic_cast<FGAICarrierHardware*>(base);
-    if (!ud)
-      return true;
-
-    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;
+    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;
+
+        // Get that part of the local bv tree that intersects our sphere
+        // of interrest.
+        mSubTreeCollector.setSphere(SGSphered(_center, _radius));
+        bvNode->accept(mSubTreeCollector);
     }
-    // Copy the velocity from the carrier class.
-    ud->carrier->getVelocityWrtEarth(gp.vel, gp.rot, gp.pivot);
-  
-    return true;
-  }
-
-  void fillWith(osg::Drawable* drawable)
-  {
-    bool oldSphIsec = sphIsec;
-    if (!enterBoundingSphere(drawable->getBound()))
-      return;
-
-    bool oldBackfaceCulling = mBackfaceCulling;
-    updateCullMode(drawable->getStateSet());
-
-    FGGroundCache::GroundProperty& gp = mGroundProperty;
-    // get some material information for use in the gear model
-    gp.material = globals->get_matlib()->findMaterial(drawable->getStateSet());
-    if (gp.material)
-      gp.type = gp.material->get_solid() ? FGInterface::Solid : FGInterface::Water;
-
-    drawable->accept(mTriangleFunctor);
-
-    mBackfaceCulling = oldBackfaceCulling;
-    sphIsec = oldSphIsec;
-  }
-
-  virtual void apply(osg::Geode& geode)
-  {
-    bool oldBackfaceCulling = mBackfaceCulling;
-    bool oldSphIsec = sphIsec;
-    FGGroundCache::GroundProperty oldGp = mGroundProperty;
-    if (!enterNode(geode))
-      return;
-
-    for(unsigned i = 0; i < geode.getNumDrawables(); ++i)
-      fillWith(geode.getDrawable(i));
-    sphIsec = oldSphIsec;
-    mGroundProperty = oldGp;
-    mBackfaceCulling = oldBackfaceCulling;
-  }
-
-  virtual void apply(osg::Group& group)
-  {
-    bool oldBackfaceCulling = mBackfaceCulling;
-    bool oldSphIsec = sphIsec;
-    FGGroundCache::GroundProperty oldGp = mGroundProperty;
-    if (!enterNode(group))
-      return;
-    traverse(group);
-    sphIsec = oldSphIsec;
-    mBackfaceCulling = oldBackfaceCulling;
-    mGroundProperty = oldGp;
-  }
-
-  virtual void apply(osg::Transform& transform)
-  {
-    if (!enterNode(transform))
-      return;
-    bool oldBackfaceCulling = mBackfaceCulling;
-    bool oldSphIsec = sphIsec;
-    FGGroundCache::GroundProperty oldGp = mGroundProperty;
-    /// transform the caches center to local coords
-    osg::Matrix oldLocalToGlobal = mLocalToGlobal;
-    osg::Matrix oldGlobalToLocal = mGlobalToLocal;
-    transform.computeLocalToWorldMatrix(mLocalToGlobal, this);
-    transform.computeWorldToLocalMatrix(mGlobalToLocal, this);
-
-    SGVec3d oldLocalCacheReference = mLocalCacheReference;
-    mLocalCacheReference.osg() = mCacheReference.osg()*mGlobalToLocal;
-    SGVec3d oldLocalDown = mLocalDown;
-    mLocalDown.osg() = osg::Matrixd::transform3x3(mDown.osg(), mGlobalToLocal);
-
-    // walk the children
-    traverse(transform);
-
-    // Restore that one
-    mLocalDown = oldLocalDown;
-    mLocalCacheReference = oldLocalCacheReference;
-    mLocalToGlobal = oldLocalToGlobal;
-    mGlobalToLocal = oldGlobalToLocal;
-    sphIsec = oldSphIsec;
-    mBackfaceCulling = oldBackfaceCulling;
-    mGroundProperty = oldGp;
-  }
-  
-  void addTriangle(const osg::Vec3& v1, const osg::Vec3& v2,
-                   const osg::Vec3& v3)
-  {
-    SGVec3d v[3] = {
-      SGVec3d(v1),
-      SGVec3d(v2),
-      SGVec3d(v3)
-    };
     
-    // a bounding sphere in the node local system
-    SGVec3d boundCenter = (1.0/3)*(v[0] + v[1] + v[2]);
-    double boundRadius = std::max(distSqr(v[0], boundCenter),
-                                  distSqr(v[1], boundCenter));
-    boundRadius = std::max(boundRadius, distSqr(v[2], boundCenter));
-    boundRadius = sqrt(boundRadius);
-
-    SGRayd ray(mLocalCacheReference, mLocalDown);
-
-    // if we are not in the downward cylinder bail out
-    if (!intersectsInf(ray, SGSphered(boundCenter, boundRadius + mCacheRadius)))
-      return;
+    bool testBoundingSphere(const osg::BoundingSphere& bound) const
+    {
+        if (!bound.valid())
+            return false;
 
-    SGTriangled triangle(v);
-    
-    // The normal and plane in the node local coordinate system
-    SGVec3d n = cross(triangle.getEdge(0), triangle.getEdge(1));
-    if (0 < dot(mLocalDown, n)) {
-      if (mBackfaceCulling) {
-        // Surface points downwards, ignore for altitude computations.
-        return;
-      } else {
-        triangle.flip();
-      }
+        double maxDist = bound._radius + _radius;
+        return distSqr(SGVec3d(bound._center), _center) <= maxDist*maxDist;
     }
     
-    // Only check if the triangle is in the cache sphere if the plane
-    // containing the triangle is near enough
-    if (sphIsec) {
-      double d = dot(n, v[0] - mLocalCacheReference);
-      if (d*d < mCacheRadius*dot(n, n)) {
-        // Check if the sphere around the vehicle intersects the sphere
-        // around that triangle. If so, put that triangle into the cache.
-        double r2 = boundRadius + mCacheRadius;
-        if (distSqr(boundCenter, mLocalCacheReference) < r2*r2) {
-          FGGroundCache::Triangle t;
-          t.triangle.setBaseVertex(SGVec3d(v[0].osg()*mLocalToGlobal));
-          t.triangle.setEdge(0, SGVec3d(osg::Matrixd::transform3x3(triangle.getEdge(0).osg(), mLocalToGlobal)));
-          t.triangle.setEdge(1, SGVec3d(osg::Matrixd::transform3x3(triangle.getEdge(1).osg(), mLocalToGlobal)));
-          
-          t.sphere.setCenter(SGVec3d(boundCenter.osg()*mLocalToGlobal));
-          t.sphere.setRadius(boundRadius);
-          
-          t.velocity = mGroundProperty.vel;
-          t.rotation = mGroundProperty.rot;
-          t.rotation_pivot = mGroundProperty.pivot;
-          t.type = mGroundProperty.type;
-          t.material = mGroundProperty.material;
-          mGroundCache->triangles.push_back(t);
-        }
-      }
-    }
+    SGSharedPtr<simgear::BVHNode> getBVHNode() const
+    { return mSubTreeCollector.getNode(); }
     
-    // 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.
-    SGVec3d isectpoint;
-    if (intersects(isectpoint, triangle, ray, 1e-4)) {
-      mGroundCache->found_ground = true;
-      isectpoint.osg() = isectpoint.osg()*mLocalToGlobal;
-      double this_radius = length(isectpoint);
-      if (mGroundCache->ground_radius < this_radius) {
-        mGroundCache->ground_radius = this_radius;
-        mGroundCache->_type = mGroundProperty.type;
-        mGroundCache->_material = mGroundProperty.material;
-      }
-    }
-  }
-  
-  void addLine(const osg::Vec3& v1, const osg::Vec3& v2)
-  {
-    SGVec3d gv1(osg::Vec3d(v1)*mLocalToGlobal);
-    SGVec3d gv2(osg::Vec3d(v2)*mLocalToGlobal);
-
-    SGVec3d boundCenter = 0.5*(gv1 + gv2);
-    double boundRadius = length(gv1 - boundCenter);
-
-    if (distSqr(boundCenter, mCacheReference)
-        < (boundRadius + mWireCacheRadius)*(boundRadius + mWireCacheRadius) ) {
-      if (mGroundProperty.type == FGInterface::Wire) {
-        FGGroundCache::Wire wire;
-        wire.ends[0] = gv1;
-        wire.ends[1] = gv2;
-        wire.velocity = mGroundProperty.vel;
-        wire.rotation = mGroundProperty.rot;
-        wire.rotation_pivot = mGroundProperty.pivot;
-        wire.wire_id = mGroundProperty.wire_id;
-
-        mGroundCache->wires.push_back(wire);
-      }
-      if (mGroundProperty.type == FGInterface::Catapult) {
-        FGGroundCache::Catapult cat;
-        // Trick to get the ends in the right order.
-        // Use the x axis in the original coordinate system. Choose the
-        // most negative x-axis as the one pointing forward
-        if (v1[0] > v2[0]) {
-          cat.start = gv1;
-          cat.end = gv2;
-        } else {
-          cat.start = gv2;
-          cat.end = gv1;
-        }
-        cat.velocity = mGroundProperty.vel;
-        cat.rotation = mGroundProperty.rot;
-        cat.rotation_pivot = mGroundProperty.pivot;
+private:
+    
+    SGVec3d _center;
+    double _radius;
+    double _startTime;
+    double _endTime;
 
-        mGroundCache->catapults.push_back(cat);
-      }
-    }
-  }
-
-  SGExtendedTriangleFunctor<GroundCacheFill> mTriangleFunctor;
-  FGGroundCache* mGroundCache;
-  SGVec3d mCacheReference;
-  double mCacheRadius;
-  double mWireCacheRadius;
-  osg::Matrix mLocalToGlobal;
-  osg::Matrix mGlobalToLocal;
-  SGVec3d mDown;
-  SGVec3d mLocalDown;
-  SGVec3d mLocalCacheReference;
-  bool sphIsec;
-  bool mBackfaceCulling;
-  FGGroundCache::GroundProperty mGroundProperty;
+    simgear::BVHSubTreeCollector mSubTreeCollector;
 };
 
 FGGroundCache::FGGroundCache() :
-  ground_radius(0.0),
-  cache_ref_time(0.0),
-  wire_id(0),
-  reference_wgs84_point(SGVec3d(0, 0, 0)),
-  reference_vehicle_radius(0.0),
-  found_ground(false),
-  _material(0)
+    _altitude(0),
+    _type(0),
+    _material(0),
+    cache_ref_time(0),
+    _wire(0),
+    reference_wgs84_point(SGVec3d(0, 0, 0)),
+    reference_vehicle_radius(0),
+    down(0.0, 0.0, 0.0),
+    found_ground(false)
 {
 }
 
@@ -451,275 +250,513 @@ FGGroundCache::~FGGroundCache()
 {
 }
 
-inline void
-FGGroundCache::velocityTransformTriangle(double dt,
-                                         SGTriangled& dst, SGSphered& sdst,
-                                         const FGGroundCache::Triangle& src)
-{
-  dst = src.triangle;
-  sdst = src.sphere;
-
-  if (dt*dt*dot(src.velocity, src.velocity) < SGLimitsd::epsilon())
-    return;
-
-  SGVec3d baseVert = dst.getBaseVertex();
-  SGVec3d pivotoff = baseVert - src.rotation_pivot;
-  baseVert += dt*(src.velocity + cross(src.rotation, pivotoff));
-  dst.setBaseVertex(baseVert);
-  dst.setEdge(0, dst.getEdge(0) + dt*cross(src.rotation, dst.getEdge(0)));
-  dst.setEdge(1, dst.getEdge(1) + dt*cross(src.rotation, dst.getEdge(1)));
-}
-
-
 bool
 FGGroundCache::prepare_ground_cache(double ref_time, const SGVec3d& pt,
                                     double rad)
 {
-  // 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.
-  reference_wgs84_point = pt;
-  reference_vehicle_radius = rad;
-  // Store the time reference used to compute movements of moving triangles.
-  cache_ref_time = ref_time;
-
-  // Get a normalized down vector valid for the whole cache
-  SGQuatd hlToEc = SGQuatd::fromLonLat(SGGeod::fromCart(pt));
-  down = hlToEc.rotate(SGVec3d(0, 0, 1));
-
-  // Prepare sphere around the aircraft.
-  double cacheRadius = rad;
-
-  // 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;
-  double wireCacheRadius = max_wire_dist < rad ? rad : max_wire_dist;
-
-  // Walk the scene graph and extract solid ground triangles and carrier data.
-  GroundCacheFillVisitor gcfv(this, down, pt, cacheRadius, wireCacheRadius);
-  globals->get_scenery()->get_scene_graph()->accept(gcfv);
-
-  // 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" );
-
-  return found_ground;
+    // 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()->scenery_available(geodPt.getLatitudeDeg(),
+                                                    geodPt.getLongitudeDeg(),
+                                                    rad))
+        return false;
+    _altitude = 0;
+
+    // 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 = ref_time;
+    
+    // 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
+    double endTime = cache_ref_time + 1; //FIXME??
+    CacheFill subtreeCollector(pt, rad, cache_ref_time, endTime);
+    globals->get_scenery()->get_scene_graph()->accept(subtreeCollector);
+    _localBvhTree = subtreeCollector.getBVHNode();
+
+    // Try to get a croase altitude value for the ground cache
+    SGLineSegmentd line(pt, pt + 1e4*down);
+    simgear::BVHLineSegmentVisitor lineSegmentVisitor(line, ref_time);
+    if (_localBvhTree)
+        _localBvhTree->accept(lineSegmentVisitor);
+
+    // If this is successful, store this altitude for croase altitude values
+    if (!lineSegmentVisitor.empty()) {
+        SGGeod geodPt = SGGeod::fromCart(lineSegmentVisitor.getPoint());
+        _altitude = geodPt.getElevationM();
+        _material = lineSegmentVisitor.getMaterial();
+        _type = materialToGroundType(_material);
+        found_ground = true;
+    } else {
+        // Else do a crude scene query for the current point
+        found_ground = globals->get_scenery()->
+            get_cart_elevation_m(pt, rad, _altitude, &_material);
+        _type = materialToGroundType(_material);
+    }
+    
+    // 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");
+
+    return found_ground;
 }
 
 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;
+    pt = reference_wgs84_point;
+    rad = reference_vehicle_radius;
+    ref_time = cache_ref_time;
+    return found_ground;
 }
 
+class FGGroundCache::CatapultFinder : public BVHVisitor {
+public:
+    CatapultFinder(const SGSphered& sphere, const double& t) :
+        _sphere(sphere),
+        _time(t),
+        _haveLineSegment(false)
+    { }
+    
+    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;
+
+    SGSphered _sphere;
+    double _time;
+};
+
 double
-FGGroundCache::get_cat(double t, const SGVec3d& dpt,
+FGGroundCache::get_cat(double t, const SGVec3d& pt,
                        SGVec3d end[2], SGVec3d vel[2])
 {
-  // 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) {
-    SGVec3d pivotoff, rvel[2];
-    pivotoff = catapults[i].start - catapults[i].rotation_pivot;
-    rvel[0] = catapults[i].velocity + cross(catapults[i].rotation, pivotoff);
-    pivotoff = catapults[i].end - catapults[i].rotation_pivot;
-    rvel[1] = catapults[i].velocity + cross(catapults[i].rotation, pivotoff);
-
-    SGVec3d thisEnd[2];
-    thisEnd[0] = catapults[i].start + t*rvel[0];
-    thisEnd[1] = catapults[i].end + t*rvel[1];
-
-    double this_dist = distSqr(SGLineSegmentd(thisEnd[0], thisEnd[1]), dpt);
-    if (this_dist < dist) {
-      SG_LOG(SG_FLIGHT,SG_INFO, "Found catapult "
-             << this_dist << " meters away");
-      dist = this_dist;
-        
-      end[0] = thisEnd[0];
-      end[1] = thisEnd[1];
-      vel[0] = rvel[0];
-      vel[1] = rvel[1];
-    }
-  }
+    double maxDistance = 1000;
 
-  // At the end take the root, we only computed squared distances ...
-  return sqrt(dist);
+    // Get the wire in question
+    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::get_agl(double t, const SGVec3d& dpt, double max_altoff,
+FGGroundCache::get_agl(double t, const SGVec3d& pt, double max_altoff,
                        SGVec3d& contact, SGVec3d& normal, SGVec3d& vel,
                        int *type, const SGMaterial** material, double *agl)
 {
-  bool ret = false;
-
-  *type = FGInterface::Unknown;
-//   *agl = 0.0;
-  if (material)
-    *material = 0;
-  vel = SGVec3d(0, 0, 0);
-  contact = SGVec3d(0, 0, 0);
-  normal = SGVec3d(0, 0, 0);
-
-  // Time difference to th reference time.
-  t -= cache_ref_time;
-
-  // The double valued point we start to search for intersection.
-  SGVec3d pt = dpt;
-  // shift the start of our ray by maxaltoff upwards
-  SGRayd ray(pt - max_altoff*down, down);
-
-  // Initialize to something sensible
-  double current_radius = 0.0;
-
-  size_t sz = triangles.size();
-  for (size_t i = 0; i < sz; ++i) {
-    SGSphered sphere;
-    SGTriangled triangle;
-    velocityTransformTriangle(t, triangle, sphere, triangles[i]);
-    if (!intersectsInf(ray, sphere))
-      continue;
-
-    // Check for intersection.
-    SGVec3d isecpoint;
-    if (intersects(isecpoint, triangle, ray, 1e-4)) {
-      // Compute the vector from pt to the intersection point ...
-      SGVec3d off = isecpoint - pt;
-      // ... and check if it is too high or not
-
-      // compute the radius, good enough approximation to take the geocentric radius
-      double radius = dot(isecpoint, isecpoint);
-      if (current_radius < radius) {
-        current_radius = radius;
-        ret = true;
-        // Save the new potential intersection point.
-        contact = isecpoint;
-        // The first three values in the vector are the plane normal.
-        normal = triangle.getNormal();
-        // The velocity wrt earth.
-        SGVec3d pivotoff = pt - triangles[i].rotation_pivot;
-        vel = triangles[i].velocity + cross(triangles[i].rotation, pivotoff);
-        // Save the ground type.
-        *type = triangles[i].type;
-        *agl = dot(down, contact - dpt);
+    // Just set up a ground intersection query for the given point
+    SGLineSegmentd line(pt - max_altoff*down, pt + 1e4*down);
+    simgear::BVHLineSegmentVisitor lineSegmentVisitor(line, t);
+    if (_localBvhTree)
+        _localBvhTree->accept(lineSegmentVisitor);
+
+    if (!lineSegmentVisitor.empty()) {
+        // Have an intersection
+        contact = lineSegmentVisitor.getPoint();
+        normal = lineSegmentVisitor.getNormal();
+        if (0 < dot(normal, down))
+            normal = -normal;
+        *agl = dot(down, contact - pt);
+        vel = lineSegmentVisitor.getLinearVelocity();
+        // correct the linear velocity, since the line intersector delivers
+        // values for the start point and the get_agl function should
+        // traditionally deliver for the contact point
+        vel += cross(lineSegmentVisitor.getAngularVelocity(),
+                     contact - line.getStart());
+        *type = materialToGroundType(lineSegmentVisitor.getMaterial());
         if (material)
-          *material = triangles[i].material;
-      }
-    }
-  }
+            *material = lineSegmentVisitor.getMaterial();
 
-  if (ret)
-    return true;
+        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);
+        *agl = geodPt.getElevationM() - _altitude;
+        geodPt.setElevationM(_altitude);
+        contact = SGVec3d::fromGeod(geodPt);
+        normal = -down;
+        vel = SGVec3d(0, 0, 0);
+        *type = _type;
+        if (material)
+            *material = _material;
 
-  // 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 = length(dpt);
-  contact = dpt;
-  contact *= ground_radius/r;
-  normal = -down;
-  vel = SGVec3d(0, 0, 0);
-  
-  // The altitude is the distance of the requested point from the
-  // contact point.
-  *agl = dot(down, contact - dpt);
-  *type = _type;
-  if (material)
-    *material = _material;
-
-  return ret;
+        return found_ground;
+    }
 }
 
-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.
-  SGTriangled triangle[2];
-  triangle[0].set(pt[0], pt[1], pt[2]);
-  triangle[1].set(pt[0], pt[2], pt[3]);
-
-  // Intersect the wire lines with each of these triangles.
-  // You have caught a wire if they intersect.
-  for (size_t i = 0; i < sz; ++i) {
-    SGVec3d le[2];
-    for (int k = 0; k < 2; ++k) {
-      le[k] = wires[i].ends[k];
-      SGVec3d pivotoff = le[k] - wires[i].rotation_pivot;
-      SGVec3d vel = wires[i].velocity + cross(wires[i].rotation, pivotoff);
-      le[k] += t*vel;
+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]);
+    }
+
+    virtual void apply(BVHGroup& leaf)
+    {
+        if (!_intersects(leaf.getBoundingSphere()))
+            return;
+
+        leaf.traverse(*this);
     }
-    SGLineSegmentd lineSegment(le[0], le[1]);
+    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);
+
+        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)
+    { }
     
-    for (int k=0; k<2; ++k) {
-      if (intersects(triangle[k], lineSegment)) {
-        SG_LOG(SG_FLIGHT,SG_INFO, "Caught wire");
-        // Store the wire id.
-        wire_id = wires[i].wire_id;
-        return true;
-      }
+    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;
+
+    SGTriangled _triangles[2];
+    double _time;
+};
 
-  return false;
+bool FGGroundCache::caught_wire(double t, const SGVec3d pt[4])
+{
+    // Get the wire in question
+    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;
+
+        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; }
+
+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) {
-        SGVec3d pivotoff = wires[i].ends[k] - wires[i].rotation_pivot;
-        vel[k] = wires[i].velocity + cross(wires[i].rotation, pivotoff);
-        end[k] = wires[i].ends[k] + t*vel[k];
-      }
-      return true;
-    }
-  }
+    // Fast return if we do not have an active wire.
+    if (!_wire)
+        return false;
+
+    // Get the wire in question
+    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();
 
-  return false;
+    // 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;
 }