[vtkusers] Problems visualing vector data using streamlines

[Sandro Carlotti]

Hello,
I am student using vtk as my final year project, my project involves reading 
in point data with associated vector and scalar data for each point (for 
example flow around an airfoil), and then visualising the flow.

I am stuck at the moment and I would greatly appreciate any help. I have 
outlined my problem below:

I am trying to visualise a vector field using streamlines and have tried 
following the examples in the two books and on the cd, but can not seem to 
make any headway.

I have structured the data following the text as field data with 7 arrays 
x,y,z,u,v,w,p.

I then read in the data and set the appropriate arrays to point, scalar and 
vector data. Then try and visualise the flow using streamlines.

When I run the program it gives the following error:

	ERROR: In vtkTubeFilter.cxx, line 121
	vtkTubeFilter (0x1c5372d8): : No input data!

Please could someone have a look at the code and let me know if they can see 
any obvious mistakes. Or if I am going about this in the wrong manner can 
you please point me in the right direction.

The following is the code I am trying to use to visualise the data:

catch {load vtktcl}
# get the interactor ui
source examplesTcl/vtkInt.tcl
source examplesTcl/colors.tcl
source examplesTcl/vtkInclude.tcl

set xAxis x
set yAxis y
set zAxis z
set vectoru u
set vectorv v
set vectorw w
set scalar p

vtkDataObjectReader read
        read SetFileName merged_grid_data.vtk2
vtkDataObjectToDataSetFilter do2ds
        do2ds SetInput [read GetOutput]
        do2ds SetDataSetTypeToPolyData
        do2ds DefaultNormalizeOff
        do2ds SetPointComponent 0 $xAxis 0
        do2ds SetPointComponent 1 $yAxis 0
        do2ds SetPointComponent 2 $zAxis 0
vtkFieldDataToAttributeDataFilter fd2ad
        fd2ad SetInput [do2ds GetOutput]
        fd2ad SetInputFieldToDataObjectField
        fd2ad SetOutputAttributeDataToPointData
        fd2ad DefaultNormalizeOff
        fd2ad SetScalarComponent 0 $scalar 0
        fd2ad SetVectorComponent 0 $vectoru 0
        fd2ad SetVectorComponent 1 $vectorv 0
        fd2ad SetVectorComponent 2 $vectorw 0
	fd2ad Update

# draw outline of area
vtkOutlineFilter outline
    outline SetInput [fd2ad GetOutput]
vtkPolyDataMapper outlineMapper
    outlineMapper SetInput [outline GetOutput]
vtkLODActor outlineActor
    outlineActor SetMapper outlineMapper
set outlineProp [outlineActor GetProperty]

# spherical seed point
vtkPointSource rake
	rake SetCenter -5 0 0.46875
	rake SetNumberOfPoints 10
vtkStreamLine streamers
	streamers SetInput [fd2ad GetOutput]
	streamers SetSource [rake GetOutput]
	streamers SetMaximumPropagationTime 1000
#	streamers SpeedScalarsOn
	streamers SetStepLength .025
	streamers SetIntegrationDirectionToIntegrateBothDirections
vtkTubeFilter tubes
	tubes SetInput [streamers GetOutput]
	tubes SetNumberOfSides 8
	tubes SetRadius 0.8
	tubes SetVaryRadiusToVaryRadiusByVector
vtkPolyDataMapper mapTubes
	mapTubes SetInput [tubes GetOutput]
	eval mapTubes SetScalarRange [[fd2ad GetOutput] GetScalarRange]
vtkLODActor tubesActor
	tubesActor SetMapper mapTubes


vtkRenderer ren1
vtkRenderWindow renWin
    renWin AddRenderer ren1
vtkRenderWindowInteractor iren
    iren SetRenderWindow renWin


# Add the actors to the renderer, set the background colour and size

ren1 AddActor tubesActor
ren1 AddActor outlineActor

vtkCamera aCam
    aCam SetFocalPoint 0.00657892 0 2.41026
    aCam SetPosition -1.94838 -47.1275 39.4607
    aCam ComputeViewPlaneNormal
    aCam SetViewPlaneNormal -0.0325936 -0.785725 0.617717
    aCam SetViewUp 0.00653193 0.617865 0.786257
    aCam SetClippingRange 1 100

ren1 SetBackground .1 .2 .4
ren1 SetActiveCamera aCam
renWin SetSize 600 600

iren Initialize
renWin Render

# render the image
#
iren SetUserMethod {wm deiconify .vtkInteract}

renWin Render
# render the image
iren SetUserMethod {wm deiconify .vtkInteract}

# prevent the tk window from showing up then start the event loop
wm withdraw .

Thanks for your time
Regards
Sandro
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