The Alembic data streaming can optionally interpolate between vertex of
two adjacent frames in order to smooth out the transition between
frames.
However, the decision to interpolate is only based on the vertex count.
This is not too robust as topology/connectivity can still differ even if
the number of vertices is the same (for example physics simulations and
videogrammetry can be set to output the same vertex count, but optimize
the triangle placement). This lead to vertices of unrelated polygons
being interpolated across frames.
To fix this, we now also check if the connectivity across frames is the
same, instead of just checking the topology counters. Although the bug
is revealed by the vertex interpolation routine, a similar fix is applied
to the check on topology change used to decide if the modifier has to be
evaluated for orco evaluation.
Pull Request: #105867
Kévin Dietrich
ae5fc2a7f8