Possible issue with Loci.remap()

I am trying to remap a loci based on a different structure using Loci.remap(). Sometimes this works, but sometimes it doesn’t and the output loci is empty (even if it shouldn’t be).

I have found the possible issue here: https://github.com/molstar/molstar/blob/0f5a6194ffc83b9963c2ce41e84f2625da00f203/src/mol-model/structure/structure/element/loci.ts#L152-L153

This issue could be entirely due to my wrong interpretation of how remap method should be used, but I have found that if i compare against unit.invariantId instead of unit.id everything seems to work fine.

if i get the unit in this way, it seems to work fine in every case in my code.

  let unit
   structure.units.forEach(u => {
      if (u.invariantId === invId) unit = u
   });
  if (!unit) return

[dsehnal]

Instead what does chainGroupId represents?

All instances of the same unit have the same chainGroupId. Mol* doesn’t do “physical” copies of chains when rendering instances and this helps with performance of some algorithms.

[dsehnal]

invariantId will stay the between instanced copies of the same change (e.g. when creating an assembly/symmetry).

From the code:

        /** invariant ID stays the same even if the Operator/conformation changes. */
        readonly invariantId: number,