[vtk-developers] DoublePi proposal

[Berk Geveci]

+1

I would get rid of DoublePi in 6.0 since we are cleaning up so much stuff.

On Thu, Mar 1, 2012 at 12:57 AM, David Gobbi <david.gobbi at gmail.com> wrote:

> Well, I looked through VTK to see how vtkMath::Pi() was being used,
> and now I don't think that there is any reason for a single-precision
> pi at all.  In VTK 6, vtkMath::Pi() should return a double-precision
> value, period.
>
> I found 62 classes that call vtkMath::Pi().  Only one of them,
> vtkExodusReader, seemed to have a reason for using a single-precision
> value.  The others should have switched to vtkMath::DoublePi() a long
> time ago.  My only guess as to why they weren't is that they were
> missed during the big float-to-double conversion that occurred when
> VTK 4.4 was released.
>
> So my new proposal is to do nothing for VTK 5.10 (because
> vtkMath::FloatPi() isn't really needed for anything), but to still
> change vtkMath::Pi() to "double" for VTK 6.  Then eventually
> vtkMath::DoublePi() can be deprecated.
>
>  - David
>
>
>
> On Wed, Feb 29, 2012 at 5:17 PM, David Gobbi <david.gobbi at gmail.com>
> wrote:
> > Hi J-C,
> >
> > All of those are good examples of why vtkMath:Pi() should be
> > returning double instead of float... in each of those four locations,
> > a double-precision Pi should be used instead of a single-precision Pi.
> > So don't changed them to FloatPi().
> >
> > I've also noticed that many of the vtkParametricFunction subclasses in
> > VTK are using vtkMath::Pi() when they should be using  double-precision
> pi.
> >
> >  - David
> >
> >
> > On Wed, Feb 29, 2012 at 4:44 PM, Jean-Christophe Fillion-Robin
> > <jchris.fillionr at kitware.com> wrote:
> >> Within Slicer vtkMath::Pi() is called at four location.  See details
> below.
> >>
> >> We will make sure to use vtkMath::FloatPi() when we will integrate VTK
> 5.10.
> >>
> >> Thanks
> >> Jc
> >>
> >>
> >>
> >> Modules/Loadable/Annotations/VTKWidgets/vtkAnnotationGlyphSource2D.cxx
> >> 352:  theta = 2.0 * vtkMath::Pi() / 8.0;
> >>
> >> Libs/MRML/Logic/vtkMRMLSliceLogic.cxx
> >> 2128:    double
> axisMisalignmentDegrees=acos(dotProd)*180.0/vtkMath::Pi();
> >>
> >> Libs/vtkTeem/vtkPreciseHyperStreamline.cxx
> >> 591:  vtkFloatingPointType theta=2.0*vtkMath::Pi()/this->NumberOfSides;
> >>
> >> Base/Logic/vtkSlicerGlyphSource2D.cxx
> >> 346:  theta = 2.0 * vtkMath::Pi() / 8.0
> >>
> >>
> >> On Wed, Feb 29, 2012 at 6:41 PM, Jean-Christophe Fillion-Robin
> >> <jchris.fillionr at kitware.com> wrote:
> >>>
> >>> +1 :)
> >>>
> >>>
> >>> On Wed, Feb 29, 2012 at 4:57 PM, David Gobbi <david.gobbi at gmail.com>
> >>> wrote:
> >>>>
> >>>> Hi All,
> >>>>
> >>>> I'm wondering if, for VTK 6, we can make the vtkMath::Pi() return a
> >>>> double instead of a float.  Currently, most VTK code is calling
> >>>> vtkMath::DoublePi() and, in my opinion, vtkMath::Pi() is more
> >>>> readable.
> >>>>
> >>>> Here's my proposal:
> >>>>
> >>>> 1) In VTK 5.10, a vtkMath::FloatPi() method would be added.  Any VTK
> >>>> 5.10 code that calls vtkMath::Pi() would be changed to call
> >>>> vtkMath::FloatPi() instead.
> >>>>
> >>>> 2) In VTK 6, vtkMath::Pi() would be changed so that it returns double,
> >>>> and then all instances of vtkMath::DoublePi() can be changed to
> >>>> vtkMath::Pi() to improve readability.
> >>>>
> >>>> If anyone thinks this is a good idea, I can submit a patch for the VTK
> >>>> 5.10 changes to gerrit.
> >>>>
> >>>>
> >>>> To reiterate what I'm proposing, in VTK 5.10, the following methods
> would
> >>>> exist:
> >>>>
> >>>> double vtkMath::DoublePi();
> >>>> float vtkMath::Pi();
> >>>> float vtkMath::FloatPi();  - new method for single precision
> >>>>
> >>>> In VTK 6.0, the following methods would exist:
> >>>>
> >>>> double vtkMath::DoublePi();
> >>>> double vtkMath::Pi();
> >>>> float vtkMath::FloatPi();
> >>>>
> >>>>  - David
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> >>>
> >>>
> >>>
> >>> --
> >>> +1 919 869 8849
> >>>
> >>
> >>
> >>
> >> --
> >> +1 919 869 8849
> >>
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