From 67e8e0b28786a3f87f7cd03f50c27ead086211da Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Thu, 8 Sep 2005 18:56:37 +0000
Subject: [PATCH] Added PolytopeVisitor to SphereSegment.cpp to help cull down
 to only drawables that intersect with the frustum of the SphereSegment.
 PolytopeVisitor may eventually be pulled out to be more generally used along
 the lines of osgUtil::IntersectVisitor.

---
 src/osgSim/SphereSegment.cpp | 122 +++++++++++++++++++++++++++++++++++
 1 file changed, 122 insertions(+)

diff --git a/src/osgSim/SphereSegment.cpp b/src/osgSim/SphereSegment.cpp
index ab596b155..6ab8f33cc 100644
--- a/src/osgSim/SphereSegment.cpp
+++ b/src/osgSim/SphereSegment.cpp
@@ -2,6 +2,8 @@
 #include <osg/Notify>
 #include <osg/CullFace>
 #include <osg/LineWidth>
+#include <osg/Transform>
+#include <osg/io_utils>
 
 #include <algorithm>
 
@@ -961,9 +963,129 @@ void SphereSegment::setAllColors(const osg::Vec4& c)
     setSideColor(c);
 }
 
+////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+//
+// SphereSegment interesection code.
+
+class PolytopeVisitor : public osg::NodeVisitor
+{
+    public:
+    
+        typedef std::pair<osg::Matrix, osg::Polytope> MatrixPolytopePair;
+        typedef std::vector<MatrixPolytopePair> PolytopeStack;
+    
+        struct Hit
+        {
+            Hit(const osg::Matrix& matrix, osg::NodePath& nodePath, osg::Drawable* drawable):
+                _matrix(matrix),
+                _nodePath(nodePath),
+                _drawable(drawable) {}
+
+            osg::Matrix                 _matrix;
+            osg::NodePath               _nodePath;
+            osg::ref_ptr<osg::Drawable> _drawable;
+        };
+    
+        typedef std::vector<Hit> HitList;
+
+
+        PolytopeVisitor(const osg::Matrix& matrix, const osg::Polytope& polytope):
+            osg::NodeVisitor(osg::NodeVisitor::TRAVERSE_ACTIVE_CHILDREN)
+        {
+            _polytopeStack.push_back(MatrixPolytopePair());
+            _polytopeStack.back().first = matrix;
+            _polytopeStack.back().second.setAndTransformProvidingInverse(polytope, _polytopeStack.back().first);
+        }
+        
+        void reset()
+        {
+            _polytopeStack.clear();
+            _hits.clear();
+        }
+            
+        void apply(osg::Node& node)
+        {
+            if (_polytopeStack.back().second.contains(node.getBound()))
+            {
+                traverse(node);
+            }
+        }
+
+        void apply(osg::Transform& transform)
+        {
+            if (_polytopeStack.back().second.contains(transform.getBound()))
+            {
+                const osg::Polytope& polytope = _polytopeStack.front().second;
+
+                osg::Matrix matrix = _polytopeStack.back().first;
+                transform.computeLocalToWorldMatrix(matrix, this);
+                
+                _polytopeStack.push_back(MatrixPolytopePair());
+                _polytopeStack.back().first = matrix;
+                _polytopeStack.back().second.setAndTransformProvidingInverse(polytope, matrix);
+
+                traverse(transform);
+                
+                _polytopeStack.back();
+            }
+        }
+
+        void apply(osg::Geode& node)
+        {
+            if (_polytopeStack.back().second.contains(node.getBound()))
+            {
+                for(unsigned int i=0; i<node.getNumDrawables(); ++i)
+                {
+                    if (_polytopeStack.back().second.contains(node.getDrawable(i)->getBound()))
+                    {
+                        _hits.push_back(Hit(_polytopeStack.back().first,getNodePath(),node.getDrawable(i)));
+                    }
+
+                }
+            
+                traverse(node);
+            }
+        }
+
+        HitList& getHits() { return _hits; }
+
+    protected:
+        
+        PolytopeStack   _polytopeStack;
+        HitList         _hits;
+
+};
+
+
 SphereSegment::LineList SphereSegment::computeIntersection(osg::Node* subgraph, const osg::Matrixd& transform)
 {
     osg::notify(osg::NOTICE)<<"Creating line intersection between sphere segment and subgraph."<<std::endl;
     SphereSegment::LineList lines;
+    
+    osg::BoundingBox bb = getBoundingBox();
+
+    osg::Polytope polytope;
+    polytope.add(osg::Plane(1.0,0.0,0.0,-bb.xMin())); 
+    polytope.add(osg::Plane(-1.0,0.0,0.0,bb.xMax())); 
+    polytope.add(osg::Plane(0.0,1.0,0.0,-bb.yMin())); 
+    polytope.add(osg::Plane(0.0,-1.0,0.0,bb.yMax())); 
+    polytope.add(osg::Plane(0.0,0.0,1.0,-bb.zMin())); 
+    polytope.add(osg::Plane(0.0,0.0,-1.0,bb.zMax())); 
+    
+    osg::Plane pl;
+    pl.set(osg::Vec3(-1.0,0.0,0.0), bb.corner(0));
+    PolytopeVisitor polytopeVisitor(transform, polytope);
+    
+    subgraph->accept(polytopeVisitor);
+
+    if (polytopeVisitor.getHits().empty())
+    {
+        osg::notify(osg::NOTICE)<<"No hits found."<<std::endl;
+    }
+    else
+    {
+        osg::notify(osg::NOTICE)<<"Hits found. "<<polytopeVisitor.getHits().size()<<std::endl;
+    }
+
     return lines;
 }