Jérôme Hénin

How much of the current metaD implementation is generic and could be folded back into the grid class? If you can do that, I'm happy to work it into the...

Sounds good! At least it's a plan.

@HanatoK Yes,I think all grids need to be expanded at the same time to be the same size.

In-person conversation JH & GF: need to bring this up with NAMD developers.

Here is a minimalist example. Pathological behavior happens around the half box size. Here, a distance that is exactly half the box length in y becomes 0. [PBC_bug_example.zip](https://github.com/Colvars/colvars/files/3014486/PBC_bug_example.zip)

Comment from Jim Phillips: > The Lattice::delta() function is meant for things like bonded terms. If you want the true nearest image you want a variant of Lattice::wrap_nearest_delta().

I suppose the question is: how much tilt factor should Colvars support? The case that initially brought the issue to my attention was a truncated octahedral box. I think it...

This is very much connected to issue #61 - the plan described there to move to flat arrays of shape xyzxyz could be amended.

Another route would be moving gradients to the cvc objects - at least that seems more intuitive.

This means that at some point, when a CVC applies a force to an atom group, the atom group will have to look up among its stored gradients which ones...