  The flocking of self-propelled particles in heterogeneous environments is
relevant to both natural and artificial systems. The Vicsek model is a
canonical choice to investigate such systems due to the minimal number of
parameters required to define flocking. Prior research on the Vicsek model has
investigated the effects of interaction rules, particle speed, and obstacle
packing on the flocking behavior, but the effect of interaction radius remains
an open question. Unlike obstacle-free domains, the locality of interactions
not only affects how quickly the system can become polarized, but also how well
the flocks can align or realign after colliding with obstacles. In this letter,
we delve into this subtle relationship that exists in the scale of the
perception of Vicsek particles in the presence of obstacles. We demonstrate
that the presence of obstacles impacts group density, which provides the basis
to identify distinct phases for collective behavior. This leads to the
counter-intuitive result that obstacles, while generally confounding for
macroscopic order, may enable global order even as noise in the system
increases.
