- /python/pystencils_walberla/jinja_filters.py
- /python/lbmpy_walberla/templates/BoundaryCollection.tmpl.h

staggered boundary generation: direction index should point to fluid cell when inner_or_boundary=False

In that case, the index vector contains the boundary cells, so the direction should point to the fluid cell.
When inner_or_boundary=True, the index vector contains the fluid cells and the direction points to the boundary cell.