[vtkusers] Isosurface Extraction

[Bill Lorensen]

Your isosurface only has one scalar value (the value of the
isosurface). Therefore it can only have one color. That color can come
from the lookup table (if ScalarVisibility in On) or the actor (if
ScalarVisibility is Off).

However, you can generate several isosurfaces in one call to ContourFilter.

iso->SetValue(0, -3)
iso->SetValue(1,2.1)
iso->SetValue(2,4.6) etc.

Then each isosurface will have a different scalar value.

Bill

On Tue, Apr 15, 2008 at 8:10 AM,  <r.jamieson at reading.ac.uk> wrote:
> Hi Bill,
>
> Thanks, i can now generate an isosurface, but it is all the same colour even
> if i change values, what i would like is to set the isosurface to blue (min
> value) and red (max value) with the scalar range that i have. i have tried
> the following like you suggested.
>
>
> //Create an iso-surface using Marching Cubes
> vtkContourFilter *iso = vtkContourFilter::New();
>   iso->SetInputConnection(dataSource->GetOutputPort());
>   iso->ComputeScalarsOn();
>   iso->SetValue(0, 2.1);
>
>   iso->Update();
>
> //vtkDataSetMapper *isoMapper = vtkDataSetMapper::New();
> vtkPolyDataMapper *isoMapper = vtkPolyDataMapper::New();
>   isoMapper->SetInputConnection(iso->GetOutputPort());
>   //isoMapper->ScalarVisibilityOn();
>   isoMapper->ScalarVisibilityOff();
>
>
> vtkActor *isoActor = vtkActor::New();
>   isoActor->SetMapper(isoMapper);
>   //isoActor->GetProperty()->SetColor(0.9804, 0.9216, 0.8431);
>
> ren1->AddActor(isoActor);
> // Set up the lighting.
>  //
>  vtkLight *light = vtkLight::New();
>  light->SetFocalPoint(1.875,0.6125,0);
>  light->SetPosition(0.875,1.6125,1);
>  ren1->AddLight(light);
>
>  // We want to eliminate perspective effects on the apparent lighting.
>  // Parallel camera projection will be used. To zoom in parallel projection
>  // mode, the ParallelScale is set.
>  //
>  ren1->GetActiveCamera()->SetFocalPoint(0,0,0);
>  ren1->GetActiveCamera()->SetPosition(0,0,1);
>  ren1->GetActiveCamera()->SetViewUp(0,1,0);
>  ren1->GetActiveCamera()->ParallelProjectionOn();
>  ren1->ResetCamera();
>  ren1->GetActiveCamera()->SetParallelScale(1.5);
>
> Thanks for any help
>
> Ronan
>
>
>
> On Apr 14 2008, Bill Lorensen wrote:
>
> > It should be
> > isoMapper->SetScalarRange(-7, 9);
> > actually, you don't need to specify anything if you trun
> > ScalarVisibilityOff as suggested below.
> >
> > but also, your isosurface value has to be in that range.
> >
> > Try something like:
> > iso->SetValue(0, 2);
> >
> > Finally, if you want to control the color of the actor,
> > isoMapper->ScalarVisibilityOff();
> > otherwise the actor will be colored using the resulting scalar value
> > (2 in the case above).
> >
> > Bill
> >
> >
> > On Mon, Apr 14, 2008 at 5:25 AM, ronan <r.jamieson at reading.ac.uk> wrote:
> >
> > > Hi Bill,
> > >
> > > I must have been having a mad moment yesterday, my scalar range is
> between -7 and 9, does this mean that i should have some thing like
> > >
> > > isoMapper->SetScalarRange(-7, 9);
> > >
> > > or
> > >
> > > isoMapper->SetScalarRange(0, 16);
> > >
> > >
> > > Thanks
> > >
> > > Ronan
> > >
> > >
> > >
> > > Bill Lorensen wrote:
> > > > What is the scalar range of your input?
> > > >
> > > > Bill
> > > >
> > > > On Sun, Apr 13, 2008 at 9:34 AM, ronan <r.jamieson at reading.ac.uk> >
> wrote:
> > > >
> > > >
> > > > > Hi,
> > > > >
> > > > > I am trying to get my head around isosurfaces extraction and i have
> > > tried to
> > > > > write a c++ program to do a simple extraction, but i cannot see any
> > > > > isosurfaces, i have got a wireframe box around the space...but no
> > > > > isosurface, i have attached my code
> > > > >
> > > > > I would be greatful if some one could point out where i have gone >
> > wrong.
> > > > >
> > > > > Thanks in advance
> > > > >
> > > > > Ronan
> > > > >
> > > > > int main()
> > > > > {
> > > > >
> > > > > char *c1;
> > > > > // Setup standard rendering
> > > > >
> > > > > vtkRenderer *ren1 = vtkRenderer::New();
> > > > >  ren1->SetBackground(0.8,0.8,0.8);
> > > > >
> > > > > vtkRenderWindow *renWin = vtkRenderWindow::New();
> > > > >  renWin->AddRenderer(ren1);
> > > > >  renWin->SetSize(400,300);
> > > > >
> > > > > vtkRenderWindowInteractor *iren = vtkRenderWindowInteractor::New();
> > > > > iren->SetRenderWindow(renWin);
> > > > >
> > > > > //Read data from office simulation data file
> > > > >
> > > > > vtkDataSetReader *dataSource = vtkDataSetReader::New();
> > > > >  dataSource->SetFileName("/home/ronan/Develop/Data/office.vtk");
> > > > >  dataSource->DebugOn();
> > > > >  dataSource->SetScalarsName(c1);
> > > > >  dataSource->Update();
> > > > >
> > > > > // Create and initialize a dataset outline
> > > > > // The outline of the data puts the data in context.
> > > > >
> > > > > vtkOutlineFilter *outline = vtkOutlineFilter::New();
> > > > >  outline->SetInputConnection(dataSource->GetOutputPort());
> > > > >
> > > > > vtkPolyDataMapper *outlineMapper = vtkPolyDataMapper::New();
> > > > >  outlineMapper->SetInputConnection(outline->GetOutputPort());
> > > > >
> > > > > vtkActor *outlineActor = vtkActor::New();
> > > > >  outlineActor->SetMapper(outlineMapper);
> > > > >  outlineActor->GetProperty()->SetColor(0, 0, 0);
> > > > >
> > > > > ren1->AddActor(outlineActor);
> > > > >
> > > > > //Create an iso-surface using Marching Cubes
> > > > > vtkContourFilter *iso = vtkContourFilter::New();
> > > > >  iso->SetInputConnection(dataSource->GetOutputPort());
> > > > >  iso->ComputeScalarsOn();
> > > > >  iso->SetValue(0, 14);
> > > > >  iso->Update();
> > > > >
> > > > > //vtkDataSetMapper *isoMapper = vtkDataSetMapper::New();
> > > > > vtkPolyDataMapper *isoMapper = vtkPolyDataMapper::New();
> > > > >  isoMapper->SetInputConnection(iso->GetOutputPort());
> > > > >  isoMapper->ScalarVisibilityOn();
> > > > >  isoMapper->SetScalarModeToUsePointFieldData();
> > > > >  isoMapper->SetScalarRange(0, 1200);
> > > > >
> > > > > vtkActor *isoActor = vtkActor::New();
> > > > >  isoActor->SetMapper(isoMapper);
> > > > >  isoActor->GetProperty()->SetColor(0.9804, 0.9216, 0.8431);
> > > > >
> > > > > ren1->AddActor(isoActor);
> > > > >
> > > > > renWin->Render();
> > > > >  iren->Start();
> > > > > _______________________________________________
> > > > > This is the private VTK discussion list.
> > > > > Please keep messages on-topic. Check the FAQ at:
> > > > > http://www.vtk.org/Wiki/VTK_FAQ
> > > > > Follow this link to subscribe/unsubscribe:
> > > > > http://www.vtk.org/mailman/listinfo/vtkusers
> > > > >
> > > > >
> > > > >
> > > >
> > >
> > >
> >
> >
>