Button placement is inverted.
Possible bug in void vtkTexturedButtonRepresentation::PlaceWidget(double scale, double xyz[3], double normal[3])
@L185
this->Actor->AddPosition(center[0] - xyz[0], center[1] - xyz[1], center[2] - xyz[2])
It is supposed to translate the widget actor/follower to x,y,z args but instead translates to -x, -y, -z, which doesn't seem right. TestButtonWidget
uses 0,0,0 for xyz
, this functionality isn't tested.