[vtk-developers] vtkPentagonalPrism Bug

[Bill Lorensen]

Andrew,

It is definitely as issue with the shape functions. I have played with
them a bit and also looked for info on the web. I believe the sf's
should sum to 1. But currently they only sum to one at the vertices of
the cell.

I made a change to normalize them each time they are computed. That
fixes the computed center issue, but causes other problems.

I'm hoping one of the original authors will respond.

Thanks for looking at  it,

Bill

On Tue, Jun 9, 2015 at 3:14 AM, Andrew Maclean
<andrew.amaclean at gmail.com> wrote:
> Hi Bill,
>    I played around with it today and I am pretty sure that the problem lies
> with the EXPRA ... EXPRN defines in vtkPentagonalPrism.cxx. These are used
> in InterpolationFunctions(), InterpolationDerivs().
>
> EvaluateLocation() uses InterpolationFunctions()  to determine the weights.
>
> I don't understand the mathematical basis for the calculation of these and a
> web search has not revealed anything.
>
> Regards
>     Andrew
>
>>
>> ---------- Forwarded message ----------
>> From: Bill Lorensen <bill.lorensen at gmail.com>
>> To: VTK Developers <vtk-developers at vtk.org>
>> Cc: Mathieu Malaterre <mathieu.malaterre at gmail.com>
>> Date: Sun, 7 Jun 2015 14:40:27 -0400
>> Subject: Re: [vtk-developers] vtkPentagonalPrism Bug
>> Sorry, the posted code was incorrect, but the results are still wrong...
>>
>>
>> On Sat, Jun 6, 2015 at 12:48 PM, Bill Lorensen <bill.lorensen at gmail.com>
>> wrote:
>> > Folks,
>> >
>> > I've been working on a Unit test for linear cells. So far I have found
>> > a few bugs that I could easily fix.
>> >
>> > My testing has uncovered a problem with vtkPentagonalPrism that I
>> > cannot fix on my own.
>> >
>> > If I compute the real center from the parametric center, the real
>> > center is not within the bounds of the cell. This is the only cell
>> > that fails this test.
>> >
>> > I have attached a small program and cmake file that illustrates the
>> > problem.
>> >
>> > Bill
>>
>>
>>
>> --
>> Unpaid intern in BillsBasement at noware dot com
>>
>>
> --
> ___________________________________________
> Andrew J. P. Maclean
>
> ___________________________________________



-- 
Unpaid intern in BillsBasement at noware dot com