[vtkusers] (Polydata) Vs. ( Polydata with scalar)

[qin zeng]

Hi all,

    (0) Before process:
        I have a polydata with vtkPoints (x,y) z is a constant data (for example 100).
        I have a vtkfloatarray  with the same size of vtkPoints
        My purpose: to draw a contour according vtkfloatarray value at the level of z(const)        

    1) first data set  
        I assigned the vtkfloatarray   value to z 
        so I have the polydata a set of virtual(or fake) vtkpoints (x,y,z)  (z = value of vtkfloatarray)  
        Then I use vtkSurfaceReconstructionFilter, vtkContourFilter,
        finally I got a isosurface image.
 
    2) second data set
        I still let z =(const like 100)
        Then  polydata->GetPointData()->SetScalars(vtkfloatarray)
        so I have the polydata with a set of vtkpoints(x,y, 100) with scalars.
        use vtkDelaunay2D , vtkContourFilter,

        Finally I got nothing. 


     Actually I want to draw a contour according to the scalar value ,
     not to draw a contour according to z value.

     I am just curious that, for the same data filter: contour,
     why sometimes VTK draws the image according to Z value , sometimes
     VTK draws the image according to scalar value.
    
     Any of your response is appreciated !   

Qin
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