[vtkusers] vtkProperty and Ambient/Diffuse/Specular coefficients?

[kent williams]

I have an application that creates some geometry. I recently lashed
together a dialog to manipulate the properties of the geometry --
ambient, diffuse, and specular color, etc.

I notice that vtkProperty::SetAmbient(), vtkProperty::SetDiffuse() and
vtkProperty::SetSpecular() -- act basically as binary switches --
values less than 1 turn off that aspect of object color, and values >=
1 turn it on.  SetOpacity has a similar effect -- anything less than 1
is the same as invisible.

Am I making a mistake in how I'm using vtkProperty?