osg中拾取对象和拾取点

使用osgUtil::PolytopeIntersector来拾取对象，使用这个类可与方便与点、直线等对象进行碰撞求交计算

int COSGViewInternal:PickObject(int x, int y, CObject* object)
{
  const osg::GraphicsContext::Traits* trait = m_viewer->getCamera()->getGraphicsContext()->getTraits();
  y = trait->height - y;

  double w(5.0f), h(5.0f);
  osg::ref_ptr<osgUtil::PolytopeIntersector> picker = new osgUtil::PolytopeIntersector(osgUtil::Intersector::WINDOW, x-w, y-h, x+w, y+h);
  osgUtil::IntersectionVisitor iv(picker);
  m_viewer->getCamera()->accept(iv);
  if(picker->containsIntersections())
  {
     typedef osgUtil::PolytopeIntersector::Intersections Inters;
   for(Inters::iterator it = picker->getIntersections.begin();\
   it != picker->getIntersections().end(); it++)
   {
      osg::NodePath nodepath = it->nodePath;
   unsigned int idx = nodePath.size();

   //查找交集节点路径中的最后一个节点
   obj = dynamic_cast<CObject*>(nodePath[idx -1]);
   }
  }
}

使用osgUtil::LineSegmentIntersector类来创建与对象的交点

int COSGViewInternal:PickPoint(int x, int y, osg::vec3& pnt)
{
  const osg::GraphicsContext::Traits* trait = m_viewer->getCamera()->getGraphicsContext()->getTraits();
  y = trait->height - y;
  float nx = (x - (trait->width/2.0))/(trait->width/2.0);
  float nx = (x - (trait->width/2.0))/(trait->width/2.0);
  osgUtil::LineSegmentIntersector* picker = new osgUtil::LineSegmentIntersector(osgUtil::Intersection::PROJECTION, nx, ny);
  osgUtil::IntersectionVisitor iv(picker);
  m_viewer->getCamera()->accept(iv);
  if(picker->containsIntersections())
  {
     typedef osgUtil::LineSegmentIntersector::Intersections Inters;
   for(Inters::iterator it = picker->getIntersections.begin();\
   it != picker->getIntersections().end(); it++)
   {
      osg::NodePath nodepath = it->nodePath;
   unsigned int idx = nodePath.size();

   //查找交集节点路径中的最后一个节点
  pnt = it->locakIntersectionPoint;
  normal = it->localIntersectionNormal;
  return true;
   }
  }
}