[vtkusers] Adding an Actor to a scene

[Mary Lederer]

Hi.

I've only been using VTK for a few weeks now, so forgive me if this is
an ignorant question, but here goes:

I'm trying to add a vtkFollower to a scene with one vtkActor.  I
created it, set a (new) vtkMapper for it, and added it to an
already-created vtkRenderer.  However, when I try to Render the scene
(in a vtkTkRenderWidget; I'm using Tcl/Tk), the scene doesn't visibly
change to include the new vtkFollower.  The vtkFollower's Visibility
is set to 1.  Its bounds are within the bounds of the window I'm
looking at, and its Opacity is set to 1.  The vtkRenderer has both
vtkActors in its ActorCollection.  There was one thing I found
suspicious when I called the Print command on it:

  AllocatedRenderTime: 10
  EstimatedRenderTime: 0
  RenderTimeMultiplier: 0

I tried to change the RenderTimeMultiplier, but calling
SetRenderTimeMultiplier returned an error.  Any suggestions?

Thank you,
-Maitland