[Paraview] Re: vtkPolyData

[Kent Eschenberg]

Stream Tracer and Glyph should both be connected to the output of the reader. 
The output of Glyph will be the polygons that draw the arrows.

Do you get any error messages from Stream Tracer? You will need to carefully 
set its starting point and parameters to produce streamlines. Its documentation 
says it can use "any" data type but I've never used it with just points.

Kent
Pittsburgh Supercomputing Center

Alessandro Bellina wrote:
> Kent,
> Thank you very much for your suggestion. I hadn't thought of that.
> 
> I tried it with VTK_VERTEX and I am able to see the data. I am also able to
> use the Glypth module to add arrows.
> 
> Now the StreamTracer filter just doesn't makes everything disappear. I am
> not sure if it works for this datatype. I am not sure if anybody has dealt
> with the filter. I add it after Glyph, or even before I add Glyph, and
> everything disappears.
> 
> Thank you,
> 
> Alessandro
> 
> On Jan 30, 2008 10:39 AM, Kent Eschenberg <eschenbe at psc.edu> wrote:
> 
>> It seems you want your data to be stored as an unstructured grid with
>> cells of
>> type 1 (VTK_VERTEX). At each cell you will have one attribute which is a
>> vector
>> with 3 components.
>>
>> Such a grid can be run through the Glyph module to put a line or arrow at
>> each
>> cell. Let Glyph do that - don't store the data as lines.
>>
>> I haven't tried it but vtkStreamTracer should be able to generate
>> streamlines
>> from such a grid.
>>
>> To obtain such a grid you will need to store your data in one of the file
>> formats that can represent that type of grid. For example, both the VTK
>> legacy
>> and the VTK XML file formats can do this. Their ASCII versions are easy to
>> generate.
>>
>> Kent
>> Pittsburgh Supercomputing Center
>>
>> Alessandro Bellina wrote:
>>  > Robert,
>>  > Since last time I posted this I was able to display something close to
>> what
>>  > I want to do, but not quite exactly.
>>  >
>>  > I have a 2-D vector field that changes in time. In each time step the
>> vector
>>  > has six coordinates V = {(x1,y1,z1), (x2,y2,z2)}. What I was ble to do
>>  > yesterday was plot them as <Lines>. So I did 2 points per line and that
>>  > worked OK. What I am interested in doing with this field is to plot a
>> stream
>>  > (stream tracer.) So at some timestep in the future I want to be able to
>> see
>>  > some of the old features of the previous timeteps. I think the stream
>> tracer
>>  > filter does this but I can't use it with lines. Any other filters that
>> do
>>  > this?
>>  >
>>  > The file then has <Points> <Lines>. And <Lines> have a connectivity and
>>  > offset table.
>>  >
>>  > I've seen some great renderings of stream-like behavior in ParaView.
>>  >
>>  > Ultimately I'd like to be able to color the stream to imply angle of
>>  > inclination  of the vectors with respect to a normal, I think this is
>>  > secondary.
>>  >
>>  > Thanks for your help,
>>  >
>>  > Alessandro