[vtkusers] UserTransform?

[Andrew Dolgert]

Hi Tim,

You are correct that the UserTransform is applied after the
PerspectiveTransform, but it is post-multiplied, so the transformation
pipeline looks like this:  v_screen = M_perspective * M_user * M_view *
v_world.  If you want to move points for one object in the scene, you
can use vtkActor's position and orientation or, as you have done,
transform points directly.

- Drew