[vtkusers] Point rendering : how to filter values with a vtkLookupTable

[REGAT-BARREL Aurélien]

Hello,
I have a vtkStructuredPoints which contains some interesting values but also some "empty" values (=0) that are viewed in black, all around the interesting object which is composed by points from values 1 to 255.  I would like to not see points with value zero, in order to "free" the object inside.  I tried to play with a vtkLookupTable in order to assign a null alpha value to black points (=0) but it didn't work. The mapper seems to ignore my changes to its lookuptable.  Here is an example. How can I filter black values without modifying my vtkStructuredPoints.
 
package require vtk
package require vtkinteraction
package require vtktesting
vtkMath math
# 20x10x10 points
set numberOfInputPoints 2000
vtkUnsignedCharArray scalars
for {set i 0} {$i < $numberOfInputPoints} {incr i 1} {
    scalars InsertNextTuple1 [math Random 0 255]
}
vtkStructuredPoints cloud
    cloud SetDimensions 20 10 10
    cloud SetOrigin 0 0 0
    cloud SetSpacing 1 1 1
    [cloud GetPointData] SetScalars scalars
vtkDataSetMapper mapper
    mapper SetInput cloud
    mapper SetScalarRange 0 256
vtkActor actor
    actor SetMapper mapper
vtkRenderer ren
    ren AddActor actor
    ren SetBackground 0 0 0

vtkRenderWindow renWin
renWin AddRenderer ren
vtkRenderWindowInteractor iren
iren SetRenderWindow renWin
renWin SetSize 500 500
renWin Render
iren Start
wm withdraw .
 
Later, I would like to create a slider that allows the user to filter viewed values from 0 to 255. How to do that ?
I attach a screenshot that shows my problem. I have a 3D object but I can't see it well. Black values are undesirable.
 
Thanks.
 
Aurélien


		
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