Select MeshVS elements with polyline

Hi,

I am trying to select triangles of my mesh (MeshVS_Mesh) by calling the "Select" method of my context with a polyline (point2d array of screen coordinates):

Handle(AIS_InteractiveContext) context = ...;
Handle(V3d_View) view = ...

context->OpenLocalContext(false);
aisMesh->SetMeshSelMethod(MeshVS_MSM_BOX);
int selectionMode = MeshVS_SMF_Face;
context->Load(aisObj, selectionMode, 1);

TColgp_Array1OfPnt2d polyline(1, nbVertices);
//...fill polyline point array (screenshot: green line)
m_Context->Select(polyline, view);

 

The "internal" triangles are selected as supposed. But there are also many selected triangles outside the green polyline.

I am using OpenCASCADE 6.9.1 x64, Visual Studio 2013 Pro

Any suggestions?

Regards 

Thorsten