[vtkusers] Streamlines in an Unstructured Grid

[Berk Geveci]

Erik,

For generating streamlines, your best bet is probably to use
vtkDelaunay3D. I haven't used it before so I am not sure about the
results you will get.

Also, vtkShepardMethod should copy all the vectors to the output. If
it's not, there is probably a bug/missing implementation.

-berk


On 8/1/07, E Anderson <eranders at sci.utah.edu> wrote:
> Berk,
>     I think your last question may have cleared everything up.  The
> Unstructured Grid is basically just a container for a point cloud.
> Basically, I have no connectivity at all; I have only a collection of
> points with a vector and a couple scalars attached to them (in
> vtkDataArrays).  If I need connectivity to get streamlines into this
> visualization, can you recommend a method to form the connectivity?  For
> another part of the visualization, I'm using Shepard's method to embed
> the entire volume in a rectilinear grid (for some contouring) but I
> couldn't see a way to get vectors onto each data point.
>
> Any help would be awesome, and thanks for the fast reply!
> Erik
>
> Berk Geveci wrote:
> > Your script looks fine. Is the streamline algorithm producing nothing
> > at all? Can you check the output's number of points? Can you try
> > vtkStreamTracer instead? If you are still not getting results, there
> > may be something wrong with the unstructured grid. Maybe the
> > connectivity is wrong?
> >
> > -berk
> >
> > On 7/31/07, Erik Anderson <eranders at sci.utah.edu> wrote:
> >
> >> Hi all,
> >>     I've been having some problems getting streamlines to
> >> work for me with an unstructured grid.  The Unstructured
> >> grid has points (x,y,z) and velocities contained in a
> >> vtkFloatArray named "velocity" per point.  The general
> >> pipeline I'm trying to use is as follows:
> >>
> >> vtkUnstructuredGridReader reader
> >> vtkAssignAttribute a
> >>     a.SetInput(reader.GetOutput())
> >>     a.Assign("velocity", vtkDataSetAttribute::VECTORS,
> >> vtkDataSetAttribute::VECTORS)
> >> vtkPointSource seeds
> >>     seeds.SetCenter(50, 50, 50)
> >>     seeds.SetRadius(50)
> >>     seeds.SetNumberOfPoints(50)
> >>
> >> vtkRungeKutta4 integrate
> >> vtkStreamLine streamer
> >>     streamer.SetIntegrationDirectionToIntegrateBothDirections
> >>     streamer.SetIntegrator(integrate)
> >>     streamer.SetStepLength(0.1)
> >>     streamer.SetIntegrationStepLength(0.1)
> >>     streamer.SpeedScalarsOn()
> >>
> >> vtkPolyDataMapper map
> >>     map.SetInput(streamer.GetOutput())
> >>
> >> # standard pipeline below forr rendering
> >>
> >> I am left with a blank screen (nothing rendered).  When I
> >> render the seed points, I see them in reasonable places
> >> within the volume.  Am I do ing something wrong?  Please
> >> note that the above code is more pseudo-code than a real
> >> implementation.
> >>
> >> Erik
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