[vtkusers] Streamlines source and lookup table

[A. Sottoriva]

Hi,

I'm using streamlines to visualize a vector field. I'm using
vtkPointSource as source points for my streamlines but it generates
points inside or in the surface of a sphere, I need instead to use as
source a set of points uniformly distributed over a 2D square, how can I
do ?
Besides this, I need to map all my values from blue to red and non
vice-versa as I have by default in VTK, this meands that I must flip
manually the lookup table or there is a smarter way to do it ?

Regards,

Andrea