these were only in use for assignments to a constant.
Instead of detouring all of these assignments through a temporary,
use the base field vector assignment operator to do inplace
assignments.
currently, it looks the value for ZMF is based on XMF and YMF.
ideally, the ZMF is part of the primary varialbes, it does not need to
be calculated based on XMF and YMF.
there is some refactoring that we can do here.
