  Evolved cool stars of various masses are major cosmic engines, delivering
substantial mechanical and radiative feedback to the interstellar medium
through strong stellar winds and supernova ejecta. These stars play a pivotal
role in enriching the interstellar medium with vital chemical elements that
constitute the essential building blocks for forming subsequent generations of
stars, planets, and potentially even life. Within the complex tapestry of
processes occurring in the atmospheres of these cool and luminous stars,
convection takes center stage. Convection is a non-local, complex phenomenon
marked by non-linear interactions across diverse length scales within a
multi-dimensional framework. For these particular stars, characterized by their
considerable luminosities and extensive scale heights, convection transitions
to a global scale. This transition is facilitated by transmitting radiative
energy through the non-uniform outer layers of their atmospheres. To fully
understand this phenomenon, the application of global comprehensive 3D
radiation-hydrodynamics simulations of stellar convection is of paramount
importance. We present two state-of-the-art numerical codes: CO5BOLD and
Athena++. Furthermore, we provide a view on their applications as: pivotal
roles in enabling a comprehensive investigation into the dynamic processes
linked to convection; and critical tools for accurately modeling the emissions
produced during shock breakouts in Type II-P Supernovae.
