[vtkusers] Filling vtkPoints and vtkCellArray fast

[Matt]

Thanks David.  You a were correct again.  I thought I would post my solution
for posterity's sake.

  float * pts = (float *
)Tubes->GetOutput()->GetPoints()->GetVoidPointer(0);
     - in this case I needed to cast the void pointer to the underlying data
type which was float

  int * CA = Tubes->GetOutput()->GetStrips()->GetPointer();
   - better coding would probably use vtkIdType * instead of int *

Thanks

Matt

And, then pts[0], pts[1], pts[n-1] and the same for CA

On Mon, Jan 18, 2010 at 5:41 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi Matt,
>
> I think you're looking for the GetPointer() method.  Every
> vtkDataArray has one.  It can return a pointer to the start of the
> array.
>
>   David
>
>
> On Mon, Jan 18, 2010 at 3:45 PM, Matt <pspmatt at gmail.com> wrote:
> > Ok! So, I have managed to use my underlying C arrays without much
> overhead.
> > Here, is the code:
> >
> >   float *vtkPts = (float * ) argv[0];
> >   int *vtkCells = (int * ) argv[1];
> >   int PtsArraySize = * (int *)  argv[2];
> >   int CellArraySize = * (int *)  argv[3];
> >   int nCells = * (int *) argv[4];
> >
> >   // Here comes the vtk stuff
> >
> >     vtkSmartPointer <vtkFloatArray> pts_fltarr =
> > vtkSmartPointer<vtkFloatArray>::New();
> >     pts_fltarr->SetNumberOfComponents(3); // X,Y,Z
> >     pts_fltarr->SetArray(vtkPts, PtsArraySize, 1);
> >
> >     vtkSmartPointer <vtkPoints> Points =
> vtkSmartPointer<vtkPoints>::New();
> >     Points->SetData(pts_fltarr);
> >
> >
> >     vtkSmartPointer <vtkIdTypeArray> Conn =
> > vtkSmartPointer<vtkIdTypeArray>::New();
> >     Conn->SetArray(vtkCells, CellArraySize,1);
> >
> >     vtkSmartPointer <vtkCellArray> Polys =
> > vtkSmartPointer<vtkCellArray>::New();
> >     Polys->SetCells(nCells,Conn);
> >
> >     vtkSmartPointer <vtkPolyData> Tracts = vtkSmartPointer
> > <vtkPolyData>::New();
> >
> >     Tracts->SetPoints(Points);
> >     Tracts->SetLines(Polys);
> >     Tracts->Update();
> >
> >     vtkSmartPointer <vtkTubeFilter> Tubes =
> > vtkSmartPointer<vtkTubeFilter>::New();
> >     Tubes->SetInput(Tracts);
> >     Tubes->SetRadius(.2);
> >     Tubes->SetNumberOfSides(6);
> >     Tubes->Update();
> >
> > ------------------------------
> >
> > Now, I want to pass back two new arrays to IDL that contains the point
> data
> > and the triangle strip (connectivity).
> > Again, if I could just access the arrays directly life would be much
> > simpler.  However, it appears going in reverse might be harder than what
> I
> > have already setup.
> >
> > This will give me the size needed for the arrays:
> >
> >     // pts
> >     int NumPoints = Tubes->GetOutput()->GetNumberOfPoints();
> >
> >     // cells/strips/num of elemens in array
> >     int NumConn = Tubes->GetOutput()->GetStrips()->GetSize();
> >
> > The plan would be to allocate an array of ints (vtkIdType) to hold the
> > strips and an array of floats to hold the point data.  Both, 1D.
> >
> > Strips (connectivity):
> > -------------------------------
> >
> > Tubes->GetOutput()->GetStrips()->GetData() // Will give me a
> vtkIdTypeArray
> > - but I really want is an array of vtkIdType.
> >   -- At this point, I'd like to use a getArray function like the setArray
> > function - but, it doesn't exist.
> >   -- So, do I need to loop through the whole vtkIdTypeArray and copy it
> into
> > an array of vtkIdType??
> >  -- or can I avoid this with some trick that I can't figure out?
> >
> > Points:
> > ----------
> > Tubes->GetOutput()->GetPoints() // will give me a vtkPoints object with
> all
> > of my points
> >
> > -- Again, at this point, I'd like to be able to extract the float array
> in
> > the same way I set it, i.e setdata()
> > -- I don't see a good option to do this.
> > -- Do, I need to go point-by-point filling a new float array?
> >
> >
> > Let me know if you can think of a way I can accomplish this?  I can write
> my
> > own code to it.  But, wonder if there is a way to do this and my lack of
> > experience with vtk is not allowing me to see it.
> >
> > Thanks again,
> >
> > Matt
>
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