[vtkusers] vtkMarchingCubes->vtkSmoothPolyDataFilter->vtkCurvatures

[Bill Lorensen]

Try without PolyDataNormals and Smoothing. I think the artifacts are
not Marching Cubes related.

On Mon, Jun 21, 2010 at 12:01 PM, Liam Kurmos
<quantum.leaf at googlemail.com> wrote:
> I'm trying to implement this sequence of filters on some 3d gaussian blobs.
> vtkMarchingCubes->vtkSmoothPolyDataFilter->vtkCurvatures
>
> First I tried without smoothing but then the vtkCurvatures seemed to
> be picking out artifact from the marchingCubes that were not in the
> implicit gaussians. I had partial success with smoothing (screen shots
> attached) though still some a-symmetric artifacts persist.
>
> The greatest problem is that apparently flat areas of the surface are
> being coloured the same dark blue as highly curved features implying
> this is not working. Although some feature do get the right general
> indication of colour (such as when i drop the isovalue enough that a
> flat region becomes flat enough it starts to turn green. However as
> can be seen in the screen shots, even fairly flat areas are coloured
> blue. (there are 2 disks, 2 small and 1 large blobs in the dataset)
>
> I'm pasting my code below, any advice on what im doing wrong here
> would be very much appreciated.
>
> Liam
>
> ..........
>
> iso = vtkMarchingCubes::New();
>    iso->SetInput(vol);
>    iso->SetNumberOfContours(1);
>    iso->SetValue(0, 0);
>    iso->Update();
>
>    vtkPolyDataNormals *surfNormals = vtkPolyDataNormals::New();
>    surfNormals->SetInputConnection(iso->GetOutputPort());
>    surfNormals->SetFeatureAngle(60.0);
>
>    vtkSmartPointer<vtkSmoothPolyDataFilter> smoothFilter =
>            vtkSmartPointer<vtkSmoothPolyDataFilter>::New();
>    smoothFilter->SetInputConnection(surfNormals->GetOutputPort());
>    smoothFilter->SetNumberOfIterations(5);
>    smoothFilter->SetRelaxationFactor(0.85);
>    smoothFilter->SetFeatureAngle(70);
>    smoothFilter->FeatureEdgeSmoothingOn();
>    smoothFilter->BoundarySmoothingOn();
>    smoothFilter->Update();
>
>    vtkCurvatures *curv = vtkCurvatures::New();
>    curv->SetInputConnection(smoothFilter->GetOutputPort());
>    curv->SetCurvatureTypeToMean();
>
>   //added this lookup table seems to have no affect.
>    vtkLookupTable* lut = vtkLookupTable::New();
>    lut->SetHueRange(0.0, 0.6); //Red to Blue
>    lut->SetAlphaRange(1.0, 1.0);
>    lut->SetValueRange(1.0, 1.0);
>    lut->SetSaturationRange(1.0, 1.0);
>    lut->SetNumberOfTableValues(256);
>    lut->SetRange(-100, 100);
>    lut->Build();
>
>
>    vtkPolyDataMapper *polyMap2 = vtkPolyDataMapper::New();
>    polyMap2->SetLookupTable(lut);
>    polyMap2->SetInputConnection(curv->GetOutputPort());
>
>    contourActor = vtkActor::New();
>    contourActor->SetMapper(polyMap2);
>    polyMap2->GetInput()->Update();
>
>    iso->Delete();
>
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