[vtkusers] vtkLookUpTable transparency bug?

[Artem Babayan]

Hi,

I am trying to visualise a 2D scalar field as a 3D 'landscape'. Some
of the numbers are just indicators of 'undefined' values, so I do not
want to show them at all.

I set these 'undefined' numbers to the values which correspond to the
first row of vtkLookUpTable and then assign this row 'transparent'
alpha=0:

     lut->SetTableValue(0, 0, 0, 0, 0);

However, there are 2 problems:

1) This results in 'background' color, not 'transparent' -- see second
picture -- the transparent part actually closes some part of the
graphics.
2) On one Unix system I haven't even got transparency -- the
'transparent' part was drawn in black color (as corresponds to the
table value).

So am I doing something wrong here or is it a bug in vtkLookUpTable?

Also, may be there is a smarter way not to show 'undefined' values?

Best wishes
Artem
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