irr::core::vector3df outPoint;
irr::core::triangle3df outTriangle;
const irr::scene::ISceneNode* node = 0;
irr::core::line3df ray = irr::core::line3df(begin, begin + irr::core::vector3df(dir.X, 0, dir.Z));
if (colmgr_->getCollisionPoint(ray, fieldTriangleSelector_,outPoint,outTriangle,node))
{
...
}