Problem about using TopExp_Explorer

You would have to look at some geometric attribute of the face, like the outward pointing normal or the locations of the vertices. You can not find this from a pure topological perspective.

Commenter-1

Rob Help me out..

One method is to find the normal of your face. Here is an example:

Standard_Real fUMin, fUMax, fVMin, fVMax;
BRepTools::UVBounds(face, fUMin, fUMax, fVMin, fVMax);

Standard_Real fU = (fUMax-fUMin)/2.0;
Standard_Real fV = (fVMax-fVMin)/2.0;

gp_Dir gNormal;
GeomLProp_SLProps props(BRep_Tool::Surface(face), fU, fV, 1, Precision::Confusion());
if (props.IsNormalDefined()) {
gNormal = props.Normal();
if (face.Orientation() == TopAbs_REVERSED) normal = normal * -1.0;
}

Then, take the dot product of the normal with your basic axes. A value near 1 (within some tolerance) indicates the normal mostly aligns with the axis in question, indicating the side of the box.

tks! Is there existing any sequence to construct a face byo vertexes? When I explorerde a TopoDS_Box, I got 48 vertexes!!, most of which are the same.

You get 48 vertices because the explorer visits them through the topological tree. The box has 6 faces, each with a wire. Each wire has 4 edges. Edge edge has 2 vertices. 6*4*2=48 (some of which are shared). You should actually see that there are only 8 unique vertices, each found 6 times.

Are you looking to actually construct a new face or to discover which existing vertices are part of an existing face. If the latter, you can explore the vertices for a given face and ignore duplicates or explore the face to get its wire and use a BRepTools_WireExplorer and the CurrentVertex function to get the vertices.

PS:Handle(Graphic3d_WNTGraphicDevice) TheGraphicDevice = new Graphic3d_WNTGraphicDevice();
TCollection_ExtendedString aName("OCC Viewer");
Handle(V3d_Viewer) myViewer = new V3d_Viewer(TheGraphicDevice,aName.ToExtString(),"");
myViewer->Init();
myViewer->SetDefaultLights();
myViewer->SetLightOn();
//
Handle(WNT_Window) AWNTWindow;
AWNTWindow = new WNT_Window(TheGraphicDevice,theApp.m_pMainWnd->GetSafeHwnd());
Handle(V3d_View) myView = myViewer->CreateView();
myView->SetWindow(AWNTWindow);

Cwnd->GetSafeHwnd() << I don't know how to get Cwnd->GetSafeHwnd()

Help. why no one answer my questions?

help.. i don't know how to create Cwnd->GetSafeHwnd()
it said GetSafeHwnd() unidentified so i create the following code to make Cwnd-> GetSafeHwnd():
class MFC_Tutorial_Window :public CFrameWnd
{
public:
MFC_Tutorial_Window()
{
Create(NULL,L"MFC Tutorial Part 1 CoderSource Window");
}
};

class MyApp :public CWinApp
{
MFC_Tutorial_Window *wnd;
public:
BOOL InitInstance()
{
wnd = new MFC_Tutorial_Window();
m_pMainWnd = wnd;
m_pMainWnd->ShowWindow(1);
return 1;
}
};
MyApp theApp;

----------------
instead of Cwnd->getSafehwnd(),

i wrote theApp.m_pMainwnd->getsafeHwnd()..
is it right?
do you have the sample code on displaying shape on V3d_viewer?(not the demo ones cuz it doesn't work, library files are missing. thanks
thanks