[vtk-developers] DoublePi proposal

[Andrew Maclean]

Hi Bill, David,
  As one of you pointed out earlier, the VTK Parametric classes will be
affected by this change. In particular, the regression tests will
fail due to the higher precision of Pi. I would only expect that the
pictures for the regression tests would need to be updated.

When I wrote these in conjunction with Will, I must admit I was frustrated
that vtkMath::Pi only returned float. However I made a decision to use
vtkMath::Pi rather than yet another constant for Pi in the hopes that this
would change in the future. The greater precision should improve the look
of some of the surfaces. E.g. the little imperfection at the pole of the
ellipsoid should get smaller.

Let me know if I can help in any way.

When things settle, I will also update the PDF titled "Parametric Equations
for Surfaces" in the documentation to VTK 6.

Regards
   Andrew




>
> ---------- Forwarded message ----------
> From: David Gobbi <david.gobbi at gmail.com>
> To: Bill Lorensen <bill.lorensen at gmail.com>
> Cc: VTK Developers <vtk-developers at vtk.org>
> Date: Mon, 14 May 2012 16:38:37 -0600
> Subject: Re: [vtk-developers] DoublePi proposal
> Bill, the main reason that I put my patch on hold was that I wanted to
> wait until VTK 6 had reached at least the same level of test coverage
> as VTK 5.  I still think that this is a valid reason for keeping this
> patch on hold.  The added pi precision will cause subtle changes in
> many regression images, and some of the changes will be significant
> enough to cause test failures.  That's great if all the regression
> tests are running, because we can examine any test failures that occur
> and replace the regression images as necessary.
>
> But right now in VTK 6, about half of our regression tests aren't
> running.  So if this Pi patch is pushed now, we won't see all the
> regression test failures immediately.  We'll see some regression test
> failures some weeks (or months?) later as the various tests are
> re-activated, and we won't be sure if the failures were caused by this
> patch, or if they were caused by some other patch.
>
>  - David
>
>
> On Mon, May 14, 2012 at 11:59 AM, David Gobbi <david.gobbi at gmail.com>
> wrote:
> > http://review.source.kitware.com/#/t/427/
> >
> >
> > On Mon, May 14, 2012 at 10:50 AM, Bill Lorensen <bill.lorensen at gmail.com>
> wrote:
> >> David,
> >>
> >> Can you point me to the gerrit topic? If not, I can start from scratch.
> >>
> >> Bill

-- 
___________________________________________
Andrew J. P. Maclean

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