[vtkusers] The confusion of vtkMarchingCubes

[Karthik Krishnan]

You could use vtkDiscreteMarchingCubes and color the result by cell data

or

pre-process your data to set all the non-foreground voxels to background,
(so as to make it bilelvel) and then run marching cubes to extract each
label.

On Wed, Apr 14, 2010 at 4:44 AM, 朱文武 <cool.wenwu at gmail.com> wrote:

> hi all,
>
>       A problem confused me. I need your help. The class vtkMarchingCubes
> has been adapted to construct a specified structure ( extract specified
> isosurface),  the member function— vtkMarchingCubes::setvalue(int i, double
> value) is used to specify a particular contour value.  The type of dataset i
> used was gray bmp image.  Suppose the dataset contains gray value: 91, 111,
> 121, 137.
> Now the problem is that if i want to construct the anatomy structure whose
> gray value is 111,  so the code i write is that
> SetValue(0, 111).  However,  the result of construction is that almost all
> anatomy structures whose gray value is 91, 121, 137 have been constructed
> too. Why is it happens? what's the difference between the gray value in the
> bmp image and the contour value in this function?  And how to construct a
> specified structure?
>
> If we set the parameter -value to 111,  according to the MC algorithm,
> the specified isosurface should be extracted.  Do i understand wrong !?
> On the other hand, if i want to extract multiple isosurface and control
> property of each isosurface such as colors, how to do it? The function
> SetValue(int i, double value) can not accomplish the task. Though we can add
> contour value by increasing the index-i, the output of the vtkMarchingCubes
> is combined to the subsequent filter. Can anyone provide help? Thanks very
> much !
>
> The relevant code and original image and result of the construction is
> attached:
>
> Code:
>     vtkBMPReader *Image= vtkBMPReader::New();
>     // read the dataset
>      Image->Update();
>
>     vtkMarchingCubes *skinExtractor= vtkMarchingCubes::New();//
> skinGray=220,tendon=10,radius=20,ulna=40,
>     skinExtractor->SetInputConnection(Image->GetOutputPort());
>     skinExtractor->SetValue(0,111);// input the gray value
>     skinExtractor->ComputeGradientsOn();
>     skinExtractor->ComputeScalarsOff();
>
>     vtkDecimatePro *vdeci;
>     vdeci->SetInputConnection(skinExtractor->GetOutputPort());//
>     vdeci->SetTargetReduction(0.6);//
>     vdeci->PreserveTopologyOn();//
>
>     vtkSmoothPolyDataFilter *vsmoother;
>     vsmoother->SetInputConnection(vdeci->GetOutputPort());//
>     vsmoother->SetNumberOfIterations(800);//
>
>     vtkPolyDataNormals *vskinNormal;
>     vskinNormal->SetInputConnection(vsmoother->GetOutputPort());//
>     vskinNormal->SetFeatureAngle(60.0);//
>
>     vtkPolyDataMapper *vskinMapper;
>     vskinMapper->SetInputConnection(vskinNormal->GetOutputPort());
>     vskinMapper->ScalarVisibilityOff();//
>
>     vtkActor *vskin;
>     vskin->SetMapper(vskinMapper);//
>     vskin->GetProperty()->SetColor(1,0,0);
>
> The original image :
> [image: TCVH_1300副本.bmp]
>
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