[vtkusers] Help: about ObjReader & PolyData

[Amy Henderson]

Add the line:

obj->Update();

before you ask for the number of points, cells, etc.  When you render the 
model, this call is made for you when the visualization pipeline updates.

- Amy

At 10:36 PM 8/14/2003 +0800, #LIU QIANG# wrote:
>Hi all,
>
>I encountered a problem when using vtkObjReader to import a wavefront .obj 
>file.
>
>The .obj file is consist of all triangles. I read this file with 
>vtkObjReader and it output a vtkPolyData. When I use this polydata as the 
>input of a PolyDataMapper, the renderer can render this model perfectly. 
>But when I try to access this polydata, I can't find any points or cells 
>or triangles in this polydata.
>
>Below is the C++ code:
>
>         vtkOBJReader *obj=vtkOBJReader::New();
>         obj->SetFileName("semi-sphere.obj");
>         vtkPolyData *in=obj->GetOutput();
>
>         vtkIdType  NumC=in->GetNumberOfCells ();
>         vtkIdType  NumV=in->GetNumberOfVerts ();
>         vtkIdType  NumL=in->GetNumberOfLines ();
>         vtkIdType  NumP=in->GetNumberOfPolys ();
>         vtkIdType  NumS=in->GetNumberOfStrips ();
>
>         vtkIdType NumOfPoints, PolyNum, StripNum;
>
>         NumOfPoints=in->GetNumberOfPoints();
>
>         vtkCellArray *poly, *strips;
>         poly=in->GetPolys();
>         strips=in->GetStrips();
>
>         StripNum=strips->GetNumberOfCells();
>         PolyNum=poly->GetNumberOfCells();
>----------------------------------------------------------------------------
>The result turns out that NumC, NumV, NumL, NumP, NumS, NumOfPoints, 
>PolyNum, StripNum are all 0.
>
>Can anyone help me to solve this problem and to access the points and 
>cells of the polydata? Thanks in advance.
>
>Regards,
>Patrick
>
>
>
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