[vtkusers] Filling vtkPoints and vtkCellArray fast

[Matt]

Yup, I figured that out as soon as I sent the email.

Thanks for all the help!

Matt

On Fri, Jan 15, 2010 at 3:33 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi Matt,
>
> If your vtk is built with VTK_USE_64BIT_IDS=OFF, then vtkIdType is
> just a typedef for "int" and vtkIdType will be interchangeable with
> int.  If vtkIdType is a 64-bit int (or if you want your code to work
> when vtkIdType is 64-bit) then yes, you will have to copy your int
> data into the vtkIdTypeArray.
>
>   David
>
>
> On Fri, Jan 15, 2010 at 2:03 PM, Matt <pspmatt at gmail.com> wrote:
> > Thanks so much! That was really helpful.
> > I am able to access my C array directly for vtkPoints.  That is awesome.
> > You explanation and advice really helped my understanding.
> >
> > I am now trying to figure out this vtkCellArray which I understand takes
> a
> > vtkIdTypeArray which contains vtkIdType.
> > Again, I would like to be able to access my c array directly (if
> possible).
> > Or, use the least overhead possible.
> > My c array is of type int and takes the form:  N, p1, p2, p3, N, p2,  p3,
> > p4, p5, N, .... The number of points per cell varies.
> > I guess I can't access this c array directly because it is not the right
> > type.  Seems a shame.  The data seems to be represented exactly as the
> > vtkCellArray is organized or at least in my limited understanding it
> does.
> >
> > So, what's the best plan of action?  Fill an array of vtkIdType with the
> > contents of my int c array. And, then pass that into a vtkIdTypeArray,
> which
> > I then pass onto the vtkCellArray.
> >
> > Any advice, code snippets would be much appreciated.  I am a bit stuck.
> >
> > Matt
> >
> >
> >
> > On Fri, Jan 15, 2010 at 11:03 AM, David Gobbi <david.gobbi at gmail.com>
> wrote:
> >>
> >> The vtkPoints() class has a SetData() method as you have already seen,
> >> and the vtkCellArray class has a method called SetCells(int ncells,
> >> vtkIdTypeArray *cells) that takes a vtkDataArray that contains the
> >> connectivity array.
> >>
> >> For vtkPoints::SetData(), the vtkDataArray must be either a
> >> vtkFloatArray or a vtkDoubleArray.  For vtkCellArray::SetCells(), only
> >> a vtkIdTypeArray containing "vtkIdType" values is allowed... vtkIdType
> >> is a typedef for either "int" or "long long" depending on whether
> >> VTK_USE_64BIT_IDS was set by cmake.
> >>
> >> You can efficiently set up a vtkDataArray by using the SetTuple()
> >> method, since it is an inline method.  In fact, so is the
> >> vtkPoints::SetPoint() method.
> >>
> >> If you have a huge data set and don't want to copy your data, you can
> >> have VTK use your C arrays directly.  The VTK arrays have a method
> >> called "SetArray()" that can be used like this:
> >>
> >> vtkFloatArray *array = vtkFloatArray::New();
> >> array->SetNumberOfComponents(3);
> >> array->SetArray(c_array, number_of_points*3, 1);
> >>
> >> The "1" on the end tells VTK not call "delete []" or "free()" on
> >> c_array when the vtkDataArray is freed.  You don't have to call
> >> SetNumberOfTuples() because VTK will automatically set the size of the
> >> array from the size of the c_array you give it.
> >>
> >> Note that VTK always uses vtkIdType for its cells, you can't choose
> >> whether to use 32-bit or 64-bit ids at run time.
> >>
> >>   David
> >>
> >>
> >> On Fri, Jan 15, 2010 at 9:21 AM, Matt <pspmatt at gmail.com> wrote:
> >> > Hello,
> >> >
> >> > I have recently started using VTK.  First, let me say thanks! It is
> >> > amazing.
> >> > I am working on an application in ITTVIS IDL that will communicate
> with
> >> > a
> >> > DLL (C++) that contains VTK code.
> >> > I have the DLL and the communication working fine and am able to pass
> >> > data
> >> > between the programs.
> >> > I want to make a bunch of polygons and pass them through the generate
> >> > tube
> >> > filter before passing it back to IDL.
> >> >
> >> > I am passing two arrays from IDL:
> >> >
> >> > 1) Array of points in floats. 1D.    Form:    X0 Y0 Z0 X1 Y1 Z1 X2 Y2
> Z2
> >> >
> >> > 2) Array of connectivity in int. 1D    Form:        N P0 P1 P2 N P1 P3
> N
> >> > P2
> >> > P3
> >> >
> >> >
> >> > ** I think the data is in the form that it is represented in memory in
> >> > VTK.
> >> > (As in pg. 126 4th edition, OO approach to 3D graphics)
> >> >
> >> > The usual approach would be to create a vtkPolyData array (for the
> >> > polygons), vtkPoints, and a vtkCellArray for connectivity).
> >> > And, then to fill them using vtkPoints->InsertPoint,
> >> > vtkCellArray->InsertNextCell, and then vtkPolyData->setPoints.
> >> >
> >> > However, I need this to be very effcient as I may be calling these
> >> > routines
> >> > repeatedly.  Given, that the data is almost in the form that VTK
> >> > expects.
> >> > I want to be able to stuff the data in whole vs point by point, cell
> by
> >> > cell.
> >> >
> >> > I can't seem to find a good explanation on how I would go about doing
> >> > this.
> >> >
> >> > There seems to be a ->setData method in vtkPoints class but it takes a
> >> > vtkDataArray and I currently just have a plain old array of floats.
> >> > I think the same goes for setCells in the vtkCellArray class.
> >> >
> >> > Could someone give me a quick example of the few lines of code it
> would
> >> > take
> >> > to impelement this.  Or,, point me to a resource that shows an example
> >> > of
> >> > this
> >> >
> >> > Thanks
> >> >
> >> > Matt
> >> >
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