vtkCaptionActor2D cannot change the background color

Support
1

I am using vtkCaptionActor2D in my project, and I can not specify its’ background color.

The minimal code to reproduce my question is:

import vtkmodules.all as vtk

line = vtk.vtkLineSource()
line.SetPoint1(0, 0, 0)
line.SetPoint2(1, 1, 1)
line.Update()

mapper = vtk.vtkPolyDataMapper()
mapper.SetInputData(line.GetOutput())
actor = vtk.vtkActor()
actor.SetMapper(mapper)

render = vtk.vtkRenderer()
render.AddActor(actor)
renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(render)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)
iren.SetInteractorStyle(vtk.vtkInteractorStyleTrackballCamera())

captionActor = vtk.vtkCaptionActor2D()
captionActor.SetCaption('caption')
captionActor.SetAttachmentPoint(1, 1, 1)
property = captionActor.GetCaptionTextProperty()
property.SetBackgroundColor(1, 0, 0)

render.AddActor(captionActor)

iren.Initialize()
iren.Start()

But the background color do not change:

image

I also tried captionActor.GetTextActor().GetTextProperty().SetBackgroundColor(1, 0, 0), but it still do not work.

Any suggestion is appreciated~~~

2

I find that the reason why background color do not change is: the background opacity is 0.0.

If I set the background opacity to 1.0, the SetBackgroundColor will work.