[vtkusers] place arrows equally spaced along streamlines

[Dan Lipsa]

Shawn,
I don't think this filter will work because you can interpolate in both
directions from a seed which means that you'll have a jump between some
points. Seems the easiest would be just to add an additional array in
vtkStreamTracer.

Dan


On Mon, Mar 20, 2017 at 4:39 PM, Shawn Waldon <shawn.waldon at kitware.com>
wrote:

> Not VTK, but ParaView has a vtkAppendArcLength filter [1] that you can use
> to append the distance along a polyline as a data array.  Then could you
> use that to get your evenly spaced points?  It could be moved down into VTK
> if someone needed it there.  I'm not sure how it handles multiple lines in
> the input dataset though.
>
> Shawn
>
> [1]: http://www.paraview.org/ParaView/Doc/Nightly/www/cxx-
> doc/classvtkAppendArcLength.html
>
> On Mon, Mar 20, 2017 at 4:22 PM, Andy Bauer <andy.bauer at kitware.com>
> wrote:
>
>> For this you would have to normalize the vector after doing the
>> interpolation instead of on the full velocity field.
>>
>> On Mon, Mar 20, 2017 at 4:13 PM, Andy Bauer <andy.bauer at kitware.com>
>> wrote:
>>
>>> If exact math was done with integrating the streamlines you should get
>>> the same result, regardless of the vector magnitude. Since we are
>>> numerically integrating though it may be off a bit.
>>>
>>> On Mon, Mar 20, 2017 at 4:08 PM, Cory Quammen <cory.quammen at kitware.com>
>>> wrote:
>>>
>>>> Dan,
>>>>
>>>> Actually, I think I'm wrong. I think you would get different
>>>> streamline results by changing the vector magnitudes. You'll
>>>> definitely get evenly spaced glyphs by normalizing, though :-) Too bad
>>>> the streamlines will be wrong.
>>>>
>>>> I can't think of any other tricks using existing tools in VTK to do
>>>> this - you would need a scalar field along the streamline giving the
>>>> distance from seed point.
>>>>
>>>> Cory
>>>>
>>>> On Wed, Mar 15, 2017 at 9:20 PM, Dan Lipsa <dan.lipsa at kitware.com>
>>>> wrote:
>>>> > Thanks Cory!
>>>> > This works very nice!
>>>> >
>>>> > Dan
>>>> >
>>>> >
>>>> > On Wed, Mar 15, 2017 at 12:08 PM, Cory Quammen <
>>>> cory.quammen at kitware.com>
>>>> > wrote:
>>>> >>
>>>> >> Dan,
>>>> >>
>>>> >> Another way would be to normalize your vector field, run the stream
>>>> >> tracer on it, and then contour by integration time. That should give
>>>> >> you evenly spaced samples along the streamline when you run the
>>>> >> contour filter on it.
>>>> >>
>>>> >> A quick test of this in ParaView looks like it should work. See
>>>> >> attached images. The one with the normalized velocity field has even
>>>> >> spacing, the one with the non-normalized velocity field does not.
>>>> >>
>>>> >> Cory
>>>> >>
>>>> >> On Wed, Mar 15, 2017 at 11:44 AM, Dan Lipsa <dan.lipsa at kitware.com>
>>>> wrote:
>>>> >> > Hi all,
>>>> >> > I would like to place arrow glyphs equally spaced along
>>>> streamlines. I
>>>> >> > am
>>>> >> > using vtkStreamTracer.
>>>> >> > The only way I see to do this is to add an option to
>>>> vtkStreamTracer to
>>>> >> > compute the distance from the seed and add this as a point data to
>>>> the
>>>> >> > the
>>>> >> > streamline. Than, I can use contour to get the points where I need
>>>> to
>>>> >> > place
>>>> >> > the arrows.
>>>> >> >
>>>> >> > Is there any other simpler way? Do you have any suggestions with
>>>> this?
>>>> >> >
>>>> >> > Thanks,
>>>> >> > Dan
>>>> >> >
>>>> >> >
>>>> >> > _______________________________________________
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>>>> >>
>>>> >>
>>>> >>
>>>> >> --
>>>> >> Cory Quammen
>>>> >> Staff R&D Engineer
>>>> >> Kitware, Inc.
>>>> >
>>>> >
>>>>
>>>>
>>>>
>>>> --
>>>> Cory Quammen
>>>> Staff R&D Engineer
>>>> Kitware, Inc.
>>>> _______________________________________________
>>>> Powered by www.kitware.com
>>>>
>>>> Visit other Kitware open-source projects at
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>>>
>>>
>>
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>
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