CComPtr< ISketchManager> iSwSketchMgr;
hr = iSwModel->get_SketchManager(&iSwSketchMgr);
ASSERT(S_OK == hr);
ASSERT(NULL != iSwSketchMgr);
CComPtr iSwSketchSeg;
 hr = iSwSketchMgr->CreateLine(0.0, 0.0, 0.0,1.0,1.0,1.0,&iSwSketchSeg);

hr always return false and iSwSketchSeg is always null. Do I have to add something before using the CreateLine function? Thanks!