[vtk-developers] vtk-developers Digest, Vol 95, Issue 1

[Andrew Maclean]

I would strongly support getting rid of DoublePi also it is just too
confusing. I see no reason for a FloatPi because if you really want a float
you cane just do the coercion directly as needed.

Regards
   Andrew



> ---------- Forwarded message ----------
> From: Berk Geveci <berk.geveci at kitware.com>
> To: David Gobbi <david.gobbi at gmail.com>
> Cc: VTK Developers <vtk-developers at vtk.org>
> Date: Thu, 1 Mar 2012 10:44:00 -0500
> Subject: Re: [vtk-developers] DoublePi proposal
> +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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>> >>>
>> >>>
>> >>>
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>> >>
>> >>
>> >>
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>> >>
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-- 
___________________________________________
Andrew J. P. Maclean

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