Workflow and principle of the intersection Test Module in OSG

There are three main categories:

1. osgutil: polytopeintersector // implementation class of different algorithms

2. osgutil: intersectionvisitor // used to traverse each node in the node tree

3. OSG: node * mnode; // The root node for the intersection test.

First look at usage:

 

osg::ref_ptr<osgUtil::PolytopeIntersector> intersector = new osgUtil::PolytopeIntersector(osgUtil::Intersector::WINDOW, xMin, yMin, xMax, yMax); intersector->setIntersectionLimit(osgUtil::Intersector::LIMIT_ONE_PER_DRAWABLE);osgUtil::IntersectionVisitor iv( intersector.get() );mRootNode->accept(iv);

 

Link

Osgutil: intersectionvisitor contains an osgutil: polytopeintersector instantiated object. The function is to traverse each node and transmit the information of each node to osgutil: polytopeintersector.

(Contains a series of apply methods) such:

void IntersectionVisitor::apply(osg::Group& group){    if (!enter(group)) return;    traverse(group);    leave();}void IntersectionVisitor::apply(osg::Geode& geode){    // OSG_NOTICE<<"apply(Geode&)"<<std::endl;    if (!enter(geode)) return;    // OSG_NOTICE<<"inside apply(Geode&)"<<std::endl;    for(unsigned int i=0; i<geode.getNumDrawables(); ++i)    {        intersect( geode.getDrawable(i) );    }    leave();}

The enter, leave, and intersect functions call the corresponding methods in osgutil: polytopeintersector, for example:

 inline bool enter(const osg::Node& node) { return _intersectorStack.empty() ? false : _intersectorStack.back()->enter(node); }        inline void leave() { _intersectorStack.back()->leave(); }        inline void intersect(osg::Drawable* drawable) { _intersectorStack.back()->intersect(*this, drawable); }        inline void push_clone() { _intersectorStack.push_back ( _intersectorStack.front()->clone(*this) ); }        inline void pop_clone() { if (_intersectorStack.size()>=2) _intersectorStack.pop_back(); }

In this way, almost all algorithms are concentrated in the Intersect method in osgutil: polytopeintersector.

void PolytopeIntersector::intersect(osgUtil::IntersectionVisitor& iv, osg::Drawable* drawable)

To write your own intersection test algorithm, you only need to rewrite the Intersect function.