[CONNECT C++] Basis Range vs. Element Range

What's the difference between an element range and a basis range?

DisplayHandler::GetBasisRange() Returns false (and the standard element range) if no basis range/transform is available.

In my experience, the method returns true and sets the range to zero.  mdlElement_extractRange() continues to behave as one would expect.

There's also DisplayHandler::SetBasisRange().  I don't understand what that function does.