[vtk-developers] Marking data modified

[Berk Geveci]

Can you provide a bit more detail? Who's MTime is important in this case?
Note that vtkPolyData does not take into account the MTime of the
underlying vtkCellArrays when computing its own MTime. So if the MTime of
the polydata is becoming stale, simply calling Modified() on it should be
sufficient. As far as I can tell, vtkCellArray does nothing with MTime.

On Mon, Aug 15, 2016 at 1:25 PM, Shawn Waldon <shawn.waldon at kitware.com>
wrote:

> Thanks David & Berk,
>
> Ok, I'll add a commit to my branch to update the docs and add you as
> reviewers.  I have a follow-up question though:  vtkPolyData::ReplaceCell.
> This function figures out which cell array the cell is in and then calls
> ReplaceCell on that one.  It can be in Verts, Lines, Polys, or Strips.  So
> the caller may not know which cell array to call Modified on.  What should
> we do in this case?
>
> Shawn
>
> On Mon, Aug 15, 2016 at 12:55 PM, Berk Geveci <berk.geveci at kitware.com>
> wrote:
>
>> I agree with David.
>>
>> On Mon, Aug 15, 2016 at 12:54 PM, David Cole via vtk-developers <
>> vtk-developers at vtk.org> wrote:
>>
>>> I don't specifically know the answer to this one, but in general,
>>> these sorts of things are on purpose for performance in VTK.
>>>
>>> If you want to replace 100 (or even more) cells, you'd want
>>> ReplaceCell NOT to call Modified, and just do it once at the end of
>>> your bulk replacement. I'd be surprised if somebody chimed in and
>>> contradicted this... so I would think just fixing the docs is the
>>> right way to go here.
>>>
>>>
>>> HTH,
>>> David C.
>>>
>>>
>>> On Mon, Aug 15, 2016 at 11:59 AM, Shawn Waldon <shawn.waldon at kitware.com>
>>> wrote:
>>> > Hi all,
>>> >
>>> > I have been tracking down a bug in the vtkBoxRepresentation where the
>>> > selected face never updated.  The issue was that the widget was calling
>>> > ReplaceCell on the vtkCellArray for the selected face polydata, but
>>> never
>>> > calling Modified() on the cell array (though it did call Modified() on
>>> the
>>> > polydata).  With the new OpenGL backend this matters.  The
>>> documentation for
>>> > ReplaceCell doesn't say that you have to do this afterward and the
>>> writer of
>>> > vtkBoxRepresentation used that documentation.
>>> >
>>> > So my question is this: why doesn't ReplaceCell mark the cell array as
>>> > modified? Is this a bug or on purpose for performance reasons?  I will
>>> > update the docs or fix ReplaceCell once I know which is wrong.
>>> >
>>> > Thank you,
>>> > Shawn
>>> >
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