[vtkusers] Curve / Equal Subdivision

[Bill Lorensen]

In the example I sent? I happen to be running VTK6, but there should not
have been changes.

On Thu, Jul 12, 2012 at 8:35 AM, Jean-Hugues Royer <jhroyer at joher.com>wrote:

> **
> Hi,
>
> If I do that, the first ~30 points have a distance of 1 and the rest
> 0.18648.
>
> Regards.
>
>
> On 12/07/2012 14:12, Bill Lorensen wrote:
>
> The splines are parameterized by an approximation to the arc length. Also,
> the boundary conditions of the splines can affect the shape of the spline.
> Try this version of the script:
>
>  #!/usr/bin/python
> import vtk
>
>  lineSource = vtk.vtkLineSource( )
> lineSource.SetPoint1( 0, 0, 0 )
> lineSource.SetPoint2( 95, 0 ,0 )
> lineSource.Update( )
>
>  mySpline = vtk.vtkCardinalSpline( )
> mySpline.SetLeftConstraint(2)
> mySpline.SetLeftValue(0.0)
> mySpline.SetRightConstraint(2)
> mySpline.SetRightValue(0.0)
>
>  spline = vtk.vtkSplineFilter( )
> spline.SetSpline(mySpline)
> spline.SetInputConnection( lineSource.GetOutputPort( ))
> spline.SetSubdivideToLength( )
> spline.SetLength( 0.18648 )
> spline.Update( )
>
>  points = spline.GetOutput().GetPoints()
>
>  meanDist = 0
>
>  for i in range( 1, points.GetNumberOfPoints() ):
>   pt = points.GetPoint(i)
>   ptPrec = points.GetPoint(i-1)
>   meanDist += pt[0] - ptPrec[0]
>   print 'pt[',i,'] X: ',pt[0],' | Distance with previous point:',pt[0] -
> ptPrec[0]
>
>  print 'Mean distance: ', meanDist / points.GetNumberOfPoints()
> print 'Expected number of points: ', 95./0.18648
> print 'Effective number of points: ', points.GetNumberOfPoints()
>
>
>
> On Thu, Jul 12, 2012 at 3:06 AM, Jerome Velut <jerome.velut at kitware.com>wrote:
>
>>  Hi Bill and Jean-Hugues,
>>
>> I was able to reproduce the bug for a straight line with vtk-5.10 python
>> (script attached). I also get the same spline from paraview by exposing the
>> vtkSplineFilter (hopefully!).
>>
>> Jerome
>>
>> Le 10/07/2012 19:09, Bill Lorensen a écrit :
>>
>> It is always possible that there is a bug.
>>
>> Can you provide a small, compilable example that illustrates the problem?
>>
>> On Tue, Jul 10, 2012 at 10:50 AM, Jean-Hugues Royer <jhroyer at joher.com>wrote:
>>
>>>  Hi,
>>>
>>> I also tried vtkSplineFIlter using SetSubdivideToLength() and
>>> SetLength(distance).
>>>
>>> But the result is that the points are not equally distributed.
>>>
>>> When you provide a curve the beginning and ending points are not equally
>>> distributed while the center points are.
>>>
>>> When you provide a straight line no points at all are equally
>>> distributed.
>>>
>>> I get exact same result when using
>>> vtkSplineFIlter/SetSubdivideToLength/SetLength and
>>> vtkParametricSpline/SetParametricFunction/SetUResolution.
>>>
>>> May be I'm missing something ?
>>>
>>>
>>> On 10/07/2012 16:21, Bill Lorensen wrote:
>>>
>>> Look at vtkSplineFIlter
>>> Here is one use:
>>> http://vtk.org/Wiki/VTK/Examples/Cxx/PolyData/FitSplineToCutterOutput
>>>
>>>
>>>  On Tue, Jul 10, 2012 at 9:59 AM, Jean-Hugues Royer <jhroyer at joher.com>wrote:
>>>
>>>> Hi,
>>>>
>>>> I have a curve which is a vtkPoints array.
>>>>
>>>> I would like to generate another vtkPoints array where every
>>>> consecutive points have the same distance. (basically divide the curve to n
>>>> equals segments)
>>>>
>>>> I tried to use vtkParametricSpline/vtkParametricFunctionSource but I
>>>> was only able to change the number of points to another value but I didn't
>>>> find how to specify that these new points should be equally distributed.
>>>>
>>>> Any idea ?
>>>>
>>>> _______________________________________________
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>>>
>>>
>>>
>>> --
>>> Unpaid intern in BillsBasement at noware dot com
>>>
>>>
>>
>>
>> --
>> Unpaid intern in BillsBasement at noware dot com
>>
>>
>>
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>>
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>>
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>>
>>
>>   --
>> Jérôme Velut
>> R&D Engineer
>> Kitware SAS
>> 26 rue Louis Guérin
>> 69100 Villeurbanne, France
>> F: +33 (0)4.37.45.04.15http://www.kitware.fr
>>
>>
>
>
>  --
> Unpaid intern in BillsBasement at noware dot com
>
>


-- 
Unpaid intern in BillsBasement at noware dot com
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