[vtkusers] vtkLookupTable with vtkStructuredPoints or vtkStructuredGrid : How it works ???

[REGAT-BARREL Aurélien]

Hello everybody,
I am still trying to blank zero-value points in my vtkStrcuturedPoints. I have done it via a vtkThreshold filter but it generate a new DataSet and it is very slow.
So I have tried to change black points opacity in the lookuptable build by the mapper but it fails.
Here is the interesting code :
 
    mapper = vtkDataSetMapper()
    mapper.SetInput( cloud )
    mapper.SetScalarRange( cloud.GetScalarRange() )
    lut = mapper.GetLookupTable()
    lut.Build()
    lut.SetTableValue( 0, 0, 0, 0, 0 )

It does nothing, why ?
I thought that it was a limitation of vtkStructuredGrid (because a point is used to render more than one cell, see the 2 screenshots to see what I mean) and I changed my code to use a vtkStructuredGrid. It is the same thing... Why ?
Python examples :
vtkStructuredPoints (first screenshot)
 
from vtk import *
def main():
    math = vtkMath()
    # 20x10x10 points
    nx = 20
    ny = 10
    nz = 10
    # create the cloud of 20x10x10 points
    scalars = vtkUnsignedCharArray()
    for z in range(0, nz):
        for y in range(0, ny):
            for x in range(0, nx):
                if x < 5:
                    scalars.InsertNextTuple1( 0 )
                else:
                    scalars.InsertNextTuple1( math.Random( 0, 255 ) + 1 )
    cloud = vtkStructuredPoints()
    cloud.SetDimensions( nx, ny, nz )
    cloud.SetOrigin( 0, 0, 0 )
    cloud.SetSpacing( 1, 1, 1 )
    cloud.GetPointData().SetScalars( scalars )
    # create mapper + change black points opacity
    mapper = vtkDataSetMapper()
    mapper.SetInput( cloud )
    mapper.SetScalarRange( cloud.GetScalarRange() )
    lut = mapper.GetLookupTable()
    lut.Build()
    lut.SetTableValue( 0, 0, 0, 0, 0 )
    # render it
    actor = vtkActor()
    actor.SetMapper( mapper )
    ren = vtkRenderer()
    ren.AddActor( actor )
    ren.SetBackground( 1, 1, 1 )
    renWin = vtkRenderWindow()
    renWin.AddRenderer( ren )
    iren = vtkRenderWindowInteractor()
    iren.SetRenderWindow( renWin )
    renWin.SetSize( 500, 500 )
    renWin.Render()
    iren.Start()
if __name__ == '__main__':
    main()
 
 
vtkStructuredGrid (second screenshot)
 
from vtk import *
def main():
    math = vtkMath()
    # 20x10x10 points
    nx = 20
    ny = 10
    nz = 10
    # create the cloud of 20x10x10 points
    points = vtkPoints()
    for z in range(0, nz+1):
        for y in range(0, ny+1):
            for x in range(0, nx+1):
                points.InsertNextPoint( x, y, z )
    cloud = vtkStructuredGrid()
    cloud.SetDimensions( nx + 1, ny + 1, nz + 1 )
    cloud.SetPoints( points )
    values = vtkUnsignedCharArray()
    for z in range(0, nz):
        for y in range(0, ny):
            for x in range(0, nx):
                if x < 5:
                    values.InsertNextValue( 0 )
                else:
                    values.InsertNextValue( math.Random( 0, 255 ) )
    cloud.GetCellData().SetScalars( values );
    # create mapper + change black points opacity
    mapper = vtkDataSetMapper()
    mapper.SetInput( cloud )
    mapper.SetScalarRange( cloud.GetScalarRange() )
    lut = mapper.GetLookupTable()
    lut.Build()
    lut.SetTableValue( 0, 0, 0, 0, 0 )
    # render it
    actor = vtkActor()
    actor.SetMapper( mapper )
    ren = vtkRenderer()
    ren.AddActor( actor )
    ren.SetBackground( 1, 1, 1 )
    renWin = vtkRenderWindow()
    renWin.AddRenderer( ren )
    iren = vtkRenderWindowInteractor()
    iren.SetRenderWindow( renWin )
    renWin.SetSize( 500, 500 )
    renWin.Render()
    iren.Start()
if __name__ == '__main__':
    main()
 
Thanks for your help.
 
Aurélien REGAT-BARREL
 
 


		
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