[vtkusers] Cell data in a vtkPolyData object

[Clinton Stimpson]

Did you ever try calling vtkPolyData::BuildCells() after you modify the
cells in the vtkCellArray's that a vtkPolyData references?

Clint

> ------------------------------
>
> Message: 7
> Date: Fri, 27 Aug 2004 12:39:35 +0200
> From: Sander Niemeijer <niemeijer at science-and-technology.nl>
> Subject: Re: [vtkusers] Cell data in a vtkPolyData object
> To: "Charles Boivin" <Charles.Boivin at rwdiwest.com>
> Cc: vtkusers at vtk.org
> Message-ID:
> 	<6344DBFE-F815-11D8-82AA-00039383F730 at science-and-technology.nl>
> Content-Type: text/plain; charset=US-ASCII; format=flowed
>
> Hi Charles,
>
> It's no wonder that it's puzzling you. The fact is that there is
> something very wrong with the design of the vtkPolyData class.
>
> If you use a vtkPolyData object to store only one type of cells (i.e.
> only vertices, or only lines, etc.) then everything goes well. But once
> you start to mix different types of cells in a vtkPolyData object you
> will get into all kinds of trouble.
>
> See for instance my bug report:
> http://www.vtk.org/Bug/bug.php?op=show&bugid=564&pos=0
>
> And the e-mail I send to the list about this:
> http://public.kitware.com/pipermail/vtkusers/2004-January/071326.html
>
> The only advice I can give you is to use a different vtkPolyData object
> for each cell type you have.
>
> Best regards,
> Sander
>
> On donderdag, aug 26, 2004, at 23:32 Europe/Amsterdam, Charles Boivin
> wrote:
>
> > Hello everyone,
> >
> > Well, I am still working on my custom reader, and thanks to everyone
> > here, a lot of progress has been made. I am able to load my geometry
> > and
> > connectivity properly using various types of cells (vertices, lines,
> > and
> > polygons), and that works pretty well. I have also been able to load
> > any
> > kind of point data (i.e. combinations of scalars, vectors, etc..)
> > successfully.
> >
> > I then turned my attention to cell data. Cells are stored in the
> > vtkPolyData class using different containers for vertices, lines and
> > polygons, i.e. there is a separate vtkCellArray array for vertices,
> > lines, and polygons. Those are set in vtkPolyData using
> > vtkPolyData::SetVertices(), SetLines() and SetPolys(). (I don't mean to
> > lecture anyone here, but I figured I would explain how I understand
> > things; that way it would be easy for you to point out a flaw in my
> > reasoning).
> >
> > I store my cell data in a vtkDoubleArray, and later set the cell data
> > to it using a call to
> > vtkPolyData::GetCellData()->AddArray(myCellDataArray). This is pretty
> > much the same process that I (successfully) use for node data. However,
> > things to do not look right for cell data if I have different types of
> > cells (i.e. verts, lines, and polys) in my geometry.
> >
> > When I set the data, I need to specify an index to the cell, and then
> > the data. How do I know what the index of the different cells are when
> > stored in vtkPolyData if they are not all in the same container? I know
> > the vtkCellArray::InsertCell() function returns an index to its
> > position, but, for example, the vertices array does not know about the
> > line array, and vice-versa. When I then have only *one* array for my
> > data, how do I arrange it properly so that it matches the cells?
> >
> > I hope I made myself clear... this is a bit puzzling to me!
> >
> > Thank you in advance,
> >
> > Charles Boivin
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