[Paraview] plot streamlines from rectilinear gird data

[Lianhua Zhu]

Hello all!
 I am new to paraview&vtk

I want to plot 2d velocity filed. I have googled long times, but in vain.
My .vtk file is
_______________________________
# vtk DataFile Version 2.0
out980.vtk
ASCII
DATASET RECTILINEAR_GRID
DIMENSIONS 32 32 1
X_COORDINATES 32 float
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
28 29 30 31
Y_COORDINATES 32 float
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
28 29 30 31
Z_COORDINATES 1 float
0
POINT_DATA 1024
VECTORS VecVelocity float
0              -3.49e-18         0
0              -3.49e-18         0
... 1022 more lines like above...
...
_______________________________

After import the data into paraview and click the "Stream Tracer" button ,
then apply, but the view port
became blank(nothing but coordinate axis) .

btw. The contour button is grey, Why?

Thanks!
Zhu Lianhua
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