Use the custom LineSegmentIntersector for QuadTree to simplify traversal

code

components/terrain/quadtreenode.cpp

@@ -154,18 +154,21 @@ void QuadTreeNode::traverseTo(ViewData* vd, float size, const osg::Vec2f& center
     }
 }
 
-void QuadTreeNode::traverse(osg::NodeVisitor &nv)
+void QuadTreeNode::intersect(ViewData* vd, TerrainLineIntersector* intersector)
 {
     if (!hasValidBounds())
         return;
 
-    bool needsUpdate = true;
-    ViewData* vd = getView(nv, needsUpdate);
+    if (!intersector->intersectAndClip(getBoundingBox()))
+        return;
 
-    if ((mLodCallback && mLodCallback->isSufficientDetail(this, distance(vd->getViewPoint()))) || !getNumChildren())
+    if (getNumChildren() == 0)
         vd->add(this, true);
     else
-        osg::Group::traverse(nv);
+    {
+        for (unsigned int i=0; i<getNumChildren(); ++i)
+            getChild(i)->intersect(vd, intersector);
+    }
 }
 
 void QuadTreeNode::setLodCallback(LodCallback *lodCallback)

components/terrain/quadtreenode.hpp

@@ -2,12 +2,31 @@
 #define OPENMW_COMPONENTS_TERRAIN_QUADTREENODE_H
 
 #include <osg/Group>
+#include <osgUtil/LineSegmentIntersector>
 
 #include "defs.hpp"
 
 namespace Terrain
 {
 
+    class TerrainLineIntersector : public osgUtil::LineSegmentIntersector
+    {
+    public:
+        TerrainLineIntersector(osgUtil::LineSegmentIntersector* intersector, osg::Matrix& matrix) :
+            osgUtil::LineSegmentIntersector(intersector->getStart() * matrix, intersector->getEnd() * matrix)
+        {
+            setPrecisionHint(intersector->getPrecisionHint());
+            _intersectionLimit = intersector->getIntersectionLimit();
+            _parent = intersector;
+        }
+
+        bool intersectAndClip(const osg::BoundingBox& bbInput)
+        {
+            osg::Vec3d s(_start), e(_end);
+            return osgUtil::LineSegmentIntersector::intersectAndClip(s, e, bbInput);
+        }
+    };
+
     enum ChildDirection
     {
         NW = 0,
@@ -72,9 +91,6 @@ namespace Terrain
         /// center in cell coordinates
         const osg::Vec2f& getCenter() const;
 
-        /// Traverse the child tree and populate the ViewData
-        virtual void traverse(osg::NodeVisitor& nv);
-
         /// Optimized version of traverse() that doesn't incur the overhead of NodeVisitor double-dispatch or fetching the various variables.
         /// Note this doesn't do any culling for non-cull visitors (e.g. intersections) so it shouldn't be used for those.
         void traverse(ViewData* vd, osg::NodeVisitor* nv, const osg::Vec3f& viewPoint, bool visible, float maxDist);
@@ -82,6 +98,9 @@ namespace Terrain
         /// Traverse to a specific node and add only that node.
         void traverseTo(ViewData* vd, float size, const osg::Vec2f& center);
 
+        /// Adds all leaf nodes which intersect the line from start to end
+        void intersect(ViewData* vd, TerrainLineIntersector* intersector);
+
         /// Set the Lod callback to use for determining when to stop traversing further down the quad tree.
         void setLodCallback(LodCallback* lodCallback);
 

components/terrain/quadtreeworld.cpp

@@ -360,7 +360,18 @@ void QuadTreeWorld::accept(osg::NodeVisitor &nv)
                 mRootNode->traverse(vd, &nv, cv->getViewPoint(), true, mViewDistance);
         }
         else
-            mRootNode->traverse(nv);
+        {
+            osgUtil::IntersectionVisitor* iv = static_cast<osgUtil::IntersectionVisitor*>(&nv);
+            osgUtil::LineSegmentIntersector* lineIntsersector = dynamic_cast<osgUtil::LineSegmentIntersector*>(iv->getIntersector());
+            if (!lineIntsersector)
+                throw std::runtime_error("Can not update QuadTreeWorld - the LineSegmentIntersector expected");
+
+            osg::Matrix matrix = osg::Matrix::identity();
+            if (lineIntsersector->getCoordinateFrame() == osgUtil::Intersector::CoordinateFrame::MODEL && iv->getModelMatrix() == 0)
+                matrix = lineIntsersector->getTransformation(*iv, osgUtil::Intersector::CoordinateFrame::MODEL);
+            osg::ref_ptr<TerrainLineIntersector> terrainIntersector (new TerrainLineIntersector(lineIntsersector, matrix));
+            mRootNode->intersect(vd, terrainIntersector);
+        }
     }
     else if (isCullVisitor)
     {