[Octaviz-help] Re: use data from officeTube

[Fabian B. <f.b...@gm...>]

Hi Dragan,

thanks for the quick reply. 

* On 18 Oct 2005 * Dragan Tubic wrote:

> You'll need know quite a bit about VTK to do this. Once you know which object
> contains the data you want, you can proceed in the same way as you would from
> C++ or Python. Unfortenatly, I'm too busy now to check this particular example
> but if I find some free time later this week I'll let you know.


Now, I got a 'little' bit deeper into VTK and figured out
that I could use the probe filter.

Below I want to describe what I did. I used like mentioned before the
'officeTube.m' as base.


I changed the reader to an Ensight format:

  %  This example demonstrates the use of a single streamline and the
  %  tube filter to create a streamtube.
  
  vtk_init;
  
  
  VTK_DATA_ROOT = vtkGetDataRoot();
  
  %  We read a data file the is a CFD analysis of airflow in an office
  %  (with ventilation and a burning cigarette). We force an update so
  %  that we can query the output for its length, i.e., the length of the
  %  diagonal of the bounding box. This is useful for normalizing the
  %  data.
  %reader = vtkStructuredGridReader();
  #reader = vtkEnSightGoldReader();
  reader = vtkGenericEnSightReader();
  %office.binary.vtk
  %reader.SetFileName(strcat(VTK_DATA_ROOT,"/Data/EnSight/office_ascii.case"));
  reader.SetCaseFileName(strcat(VTK_DATA_ROOT,"/Data/EnSight/office_ascii.case"));
  %reader.SetFileName(strcat(VTK_DATA_ROOT,"/Data/EnSight/office_ascii.case"));
  #reader.SetCaseFileName("/home/fab/HOME/Dissertation/CFD/Projects/Building_airflow/CFX/k-eps/smallerMesh_smooth/ascii_ensight/keps_small_smooth.case");
  reader.Update();
  
  length = reader.GetOutput().GetLength();

In order to use the probe filter, which can have a defined line as source, I
need scalars. In fact in the choosen case-file is a scalar (density), but I
want to acces the vector (velocity); so I need the 'calculator' to transform
the existing vector to a scalar.  I tried it this way:

  
  calc = vtkArrayCalculator();
  calc.SetInput(reader.GetOutput());
  calc.SetAttributeModeToUsePointData
  calc.AddScalarArrayName("vectors", 0)
  calc.SetResultArrayName("Velocity")
  calc.SetFunction("vectors_0")

I wasn't sure about the names, but 'paraview's calculator declared them like
above...

Afterwards I create a line using two points for the 'LineSource' and display it
in the graphic

  
  # Create three the line source to use for the probe lines.
  line = vtkLineSource()
  line.SetResolution(30)
  line.SetPoint1(1, 0 ,1.5)
  line.SetPoint2(1,2,1.5)
  mapline = vtkPolyDataMapper();
  mapline.SetInput(line.GetOutput());
  mapline.ScalarVisibilityOff();
  lineactor = vtkActor();
  lineactor.SetMapper(mapline);
  lineactor.GetProperty().SetColor(.8, .8, .6);

I use this line as 'input' for the probe filter and the defined 'calculator' as
'source' for the probe.
  
  # Move the line into place and create the probe filter.  For
  # vtkProbeFilter, the probe line is the input, and the underlying data
  # set is the source.
  probe = vtkProbeFilter()
  probe.SetInput(line.GetOutput())
  probe.SetSource(calc.GetOutput())

The rest is the same as in the officeTube example; I just remove some 'Actors' and added the 
density1 and momentum1 variables:
  
  
  outline = vtkStructuredGridOutlineFilter();
  outline.SetInput(reader.GetOutput());
  mapOutline = vtkPolyDataMapper();
  mapOutline.SetInput(outline.GetOutput());
  outlineActor = vtkActor();
  outlineActor.SetMapper(mapOutline);
  outlineActor.GetProperty().SetColor(0, 0, 0);
  
  %  Now create the usual graphics stuff.
  ren = vtkRenderer();
  renWin = vtkRenderWindow();
  renWin.AddRenderer(ren);
  iren = vtkRenderWindowInteractor();
  iren.SetRenderWindow(renWin);
  
  ren.AddActor(lineactor);
  ren.AddActor(outlineActor);
  #ren.AddActor(streamTubeActor);
  
  ren.SetBackground(0.4,0.4,0.4);
  
  %  Here we specify a particular view.
  aCamera = vtkCamera();
  aCamera.SetClippingRange(0.726079, 36.3039);
  aCamera.SetFocalPoint(2.43584, 2.15046, 1.11104);
  aCamera.SetPosition(-4.76183, -10.4426, 3.17203);
  aCamera.SetViewUp(0.0511273, 0.132773, 0.989827);
  aCamera.SetViewAngle(18.604);
  aCamera.Zoom(1.2);
  
  ren.SetActiveCamera(aCamera);
  renWin.SetSize(500, 300);
  
  
  % renWin.Render();
  vtkInitializeInteractor(iren);
  
  
  density1 = reader.GetOutput().GetPointData().GetScalars().GetTuple1(1);
  momentum1= reader.GetOutput().GetPointData().GetVectors().GetTuple3(1);
  
  #density1probe = probe.GetOutput().GetPointData().GetScalars().GetTuple1(1)
  

'density1' and 'momentum1' work without any problem, but using 'density1probe',
where I try to get access to the probe variables, octave crashes, because there
are no 'values'.

Actually I could use the working 'density1'/'momentum1' in combination with
some other octave function to define a line in the domain, but I am not sure,
that defining such a line and get the 'GetTuple1' to know the lines looks much
harder than using the available 'probe'!? But maybe, it is just because of a
big lack in octave and vtk knowledge. Would be nice, when
anybody have a nice suggestion, how I should do it.

I attached the adjusted 'officeTube' for better readability.

Best Greetings!
Fabian

P.S. Until now, I forgot to say to the developers: Great Work! It seems that it
will become my main visualization tool (with Paraview) :-)