[vtkusers] Relationship between MinZBound and Position for a vtkVolume

[Elvis Stansvik]

This is a very basic question, but I feel like I've missed something
fundamental.

I have a volume which I set the position for using SetPosition. I'm
not applying any other transformations such as rotation or scale.

What surprises me is that after having set the position, if I look at
the MinZBound of the volume, it doesn't correspond to the Z position I
set.

E.g. if I (after I set the position of the volume) do

    qDebug() << "MinZBound:" << volume->GetMinZBound();
    qDebug() << "Position[3]" << volume->GetPosition()[2];

I can get output such as:

    MinZBound: -0.162738
    Position[3] -0.165138

I thought that the bounds of a volume was in VTK world coordinates. If
so, shouldn't MinZBound be exactly the Z position?

Thanks for any clarifications, I've probably missed something simple.

Elvis