[vtkusers] Curve / Equal Subdivision

[Jerome Velut]

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 
> <mailto: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 <mailto: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
>
>
>
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-- 
Jérôme Velut
R&D Engineer
Kitware SAS
26 rue Louis Guérin
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F: +33 (0)4.37.45.04.15
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import vtk

lineSource = vtk.vtkLineSource( )
lineSource.SetPoint1( 0, 0, 0 )
lineSource.SetPoint2( 95, 0 ,0 )
lineSource.Update( )

spline = vtk.vtkSplineFilter( )
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()