void appendLineStrip(osg::Vec3Array* src) {
   int size = _array->size();
   _array->insert(_array->end(), src->begin(), src->end());
   _geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::LINE_STRIP, size, src->size()));
 }
 void appendPoint(const osg::Vec3& p) {
   int size = _array->size();
   _array->push_back(p);
   _geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::POINTS, size, 1));
 }
 void postProcess() {
   _geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::TRIANGLES, _array->size()-_count, _count));
   _count = 0;
 }