[vtk-developers] Adding ComputeArea() to vtkTriangle

[David Doria]

On Mon, Dec 21, 2009 at 10:53 AM, Moreland, Kenneth <kmorel at sandia.gov>wrote:

>  Yes, but the vtkCell classes (of which vtkTriangle is one) is not really
> like the vtkDataObject objects.  These classes are designed to hold methods
> for common computations.  For example, they already hold methods for
> computing interpolation, derivatives, contours, and intersections.  In this
> regard, a method to compute the length/area/volume of the cell is wholly
> appropriate.
>
> My only criticism (everyone has to have an opinion, right?) is that it
> would be helpful if there was a pure virtual method in vtkCell, perhaps
> called ComputeSize, that returned the length, area, or volume (depending on
> the dimensionality of the cell).  That way you would not have to down cast
> the vtkCell to some known subclass and hope the implementation is there.
>
> Now that I write this, it occurs to me that somewhere there is a
> vtkCellIntegrator in ParaView that does something similar.  Perhaps the
> implementation of that could be duplicated in vtkCell.
>
> -Ken
>
>
>
> On 12/18/09 12:15 PM, "Berk Geveci" <berk.geveci at kitware.com> wrote:
>
> I think Mathieu brings up an important point. I don't think this has
> any direct impact on the issue here but it is still a good one. VTK
> usually separates computation from the data structures. There is a
> good reason behind this. For example, when you are computing the
> volume of a polyhedron or performing some other numerical integration
> over it, there may be more than one way to do it numerically. Some
> more accurate but more costly, others less accurate but faster. This
> is why you don't find a lot of computational geometry related methods
> on vtkPolyData.
>
> On Fri, Dec 18, 2009 at 11:09 AM, Mathieu Malaterre
> <mathieu.malaterre at gmail.com> wrote:
> > Ok, my bad. I thought this was introducing a new framework to compute
> > 2D area which seem difficult to extend to 3d cell.
> >
> > thanks for clarification.
> >
> > On Fri, Dec 18, 2009 at 5:05 PM, Bill Lorensen <bill.lorensen at gmail.com>
> wrote:
> >> Mathieu,
> >>
> >> vtkTriangle is a cell. It is not filter. It currently has a
> >> TriangleArea() method, but it is cumbersome to use. David is proposing
> >> a convenience method to do the computation. It calls the
> >> TriangleArea() method but save the user from setting up the parameters
> >> for that call.
> >>
> >> Bill
> >>
> >> On Fri, Dec 18, 2009 at 10:54 AM, David Doria <daviddoria+vtk at gmail.com>
> wrote:
> >>> On Fri, Dec 18, 2009 at 10:51 AM, Mathieu Malaterre
> >>> <mathieu.malaterre at gmail.com> wrote:
> >>>>
> >>>> Hi David,
> >>>>
> >>>>  I do not have a strong opinion on this particular case.
> >>>>  However here is a couple of thoughts, I have from my modest
> >>>> understanding of VTK.
> >>>>  1. I would really separate source/sink from filter. You are writing a
> >>>> partial filter (aka algorithm) in a data object.
> >>>>  2. You are duplicating (possibly) code from vtkMeshQuality.
> >>>>
> >>>> 2cts
> >>>> -Mathieu
> >>>
> >>> 1) I'm not sure I follow. Isn't vtkTriangle an "object", not a "source"
> or
> >>> "filter"?
> >>> 2) That is likely the case and that is exactly my point here -
> >>> vtkMeshQuality (or anything else) should not have to implement this
> code, it
> >>> should just be able to call ComputeArea() on a triangle object.
> >>> Thanks,
> >>>
> >>> David
> >>> _______________________________________________
> >>> Powered by www.kitware.com
> >>>
> >>> Visit other Kitware open-source projects at
> >>> http://www.kitware.com/opensource/opensource.html
> >>>
> >>> Follow this link to subscribe/unsubscribe:
> >>> http://www.vtk.org/mailman/listinfo/vtk-developers
> >>>
> >>>
> >>>
> >> _______________________________________________
> >> Powered by www.kitware.com
> >>
> >> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
> >>
> >> Follow this link to subscribe/unsubscribe:
> >> http://www.vtk.org/mailman/listinfo/vtk-developers
> >>
> >>
> >
> >
> >
> > --
> > Mathieu
> > _______________________________________________
> > Powered by www.kitware.com
> >
> > Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
> >
> > Follow this link to subscribe/unsubscribe:
> > http://www.vtk.org/mailman/listinfo/vtk-developers
> >
> >
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtk-developers
>
>
>
>
>
>
Per Ken's suggestion, I am trying to implement a virtual double
ComputeSize() function for vtkCell.  There are a lot of cells! Many of which
I have no idea how to get their size. Is it acceptable to somehow commit
these changes without having all of them implemented? Something like a
filler "return 0" and a comment "this function has not yet been
implemented"?

The idea would be that then the framework is setup, so when a developer who
is familiar with the particular cell subclass sees the missing
implementation, they could easily fill it in.

Thoughts?

Thanks,

David
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://public.kitware.com/pipermail/vtk-developers/attachments/20091222/3c909fb2/attachment.html>