vtkActor.SetColor do not work for vtkContourFilter

Support
1

I have a binary mask, and I want to display the isoface. The special mask is zero for all pixel except that the intensity is one for two slice, for example


import vtkmodules.all as vtk

img = vtk.vtkImageData()

img.SetDimensions(256, 256, 256)
img.AllocateScalars(vtk.VTK_DOUBLE, 1)

# initial all zero
for i in range(256):
    for j in range(256):
        for k in range(256):
            img.SetScalarComponentFromDouble(i, j, k, 0, 0)

for i in range(64, 192):
    for j in range(64, 192):
        img.SetScalarComponentFromDouble(i, j, 128, 0, 1)

for i in range(64, 128):
    for j in range(64, 128):
        img.SetScalarComponentFromDouble(i, j, 129, 0, 1)

The mask is 256x256x256, and is initialized as zero. There are some pixels are one for 128/129 slice.

Then, I want to compute the isosurface and display it. The code is:


cf = vtk.vtkContourFilter()
cf.SetInputData(img)
cf.ComputeNormalsOn()
cf.SetValue(0, 1)
cf.Update()

mapper = vtk.vtkPolyDataMapper()
mapper.SetInputData(cf.GetOutput())
actor = vtk.vtkActor()
actor.SetMapper(mapper)
actor.GetProperty().SetColor(0, 0, 1) # set to blue color
actor.GetProperty().SetOpacity(0.2)

renderer = vtk.vtkRenderer()
renderer.AddActor(actor)
renderer.SetBackground(1, 1, 1)
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(renderer)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)
iren.Initialize()
iren.Start()

And the result is:

image

I set the color to blue by actor.GetProperty().SetColor(0, 0, 1), but there is some gray part. What’s wrong with my code? How to set the color to blue?

Any suggestion is appreciated~~~

2

Add this:

mapper.ScalarVisibilityOff()

If a data set has scalars, then vtkMapper will display the scalars and ignore the property color. The VTK contour and clip filters create scalars, so it is necessary to use SetScalarVisibilityOff() to display their output with a solid color.

3

@dgobbi Thanks for kindly reply.

Unfortunately, mapper.ScalarVisibilityOff() do not work, and the shown figure do not change.

Actually, vtk.vtkContourFilter.SetValue(0, 1) only extract one surface, thus there should by only one color. But, the resulted figure shows two color. I think the result should not be the ScalarVisibility.

4

It seems to be a problem with the normals. Where the mask is only once slice, the normals have a value of (0,0,0).

To generate a contour between values of 0 and 1, a contour value of 0.5 might work better, since it is halfway between the two values:

cf.SetValue(0, 0.5)
1 Like
5

It works. Thanks~~~