[vtkusers] Ambient color of lights has no effects on actor's ambient color

[王跃恒]

Hi all,

I have set up a very simple scene, with only one actor and one light.
I'm using python, the official 7.1.0 python bundle.

The renderer's ambient set to (0, 0, 0), using ren.SetAmbient(0, 0, 0), and
disable automatic light creation by ren.SetAutomaticLightCreation(False);
the actor's ambient set to 0.5, ambient color use the default (1, 1, 1);
the light's ambient color set to (1.0, 0, 0), I mean red, while diffuse
color and specular color set to (0, 0, 0).

I am expecting a red-ish flat color, since red (ambient) light shine on
grey (ambient) thing produces red, but I get a grey flat color.

It acts like there is always one and only one global pure white ambient
light (not the one I created), or the "ambient" acts like an emissive
component. The light I created has no effect on actor's ambient color.

I am new to VTK, where am I missing :(

The full source code is pretty short, both python2 and python3 will do:

import vtk
if __name__ == '__main__':
    # A source process object
    cube = vtk.vtkCubeSource()

    # A mapper process object
    cubeMapper = vtk.vtkPolyDataMapper()
    cubeMapper.SetInputConnection(cube.GetOutputPort())

    # An actor
    cubeActor = vtk.vtkActor()
    cubeActor.SetMapper(cubeMapper)
    prop = cubeActor.GetProperty()
    prop.SetAmbient(0.5)
    prop.SetDiffuse(0.0)
    prop.SetSpecular(0.0)

    # A renderer
    ren = vtk.vtkRenderer()
    ren.SetAmbient(0.0, 0.0, 0.0)
    ren.SetAutomaticLightCreation(False)
    ren.AddActor(cubeActor)

    light = ren.MakeLight()
    light.SetAmbientColor(1.0, 0.0, 0.0)
    light.SetDiffuseColor(0.0, 0.0, 0.0)
    light.SetSpecularColor(0.0, 0.0, 0.0)
    ren.AddLight(light)

    # A render window
    renWin = vtk.vtkRenderWindow()
    renWin.AddRenderer(ren)

    # window interation
    iren = vtk.vtkRenderWindowInteractor()
    iren.SetRenderWindow(renWin)

    iren.Initialize()
    renWin.Render()
    iren.Start()

---------------
Wang Yueheng,
Tsinghua University,
Beijing, China
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