  Reconfigurable Intelligent Surfaces (RIS) constitute a promising technology
that could fulfill the extreme performance and capacity needs of the upcoming
6G wireless networks, by offering software-defined control over wireless
propagation phenomena. Despite the existence of many theoretical models
describing various aspects of RIS from the signal processing perspective (e.g.,
channel fading models), there is no open platform to simulate and study their
actual physical-layer behavior, especially in the multi-RIS case. In this
paper, we develop an open simulation platform, aimed at modeling the
physical-layer electromagnetic coupling and propagation between RIS pairs. We
present the platform by initially designing a basic unit cell, and then
proceeding to progressively model and simulate multiple and larger RISs. The
platform can be used for producing verifiable stochastic models for wireless
communication in multi-RIS deployments, such as vehicle-to-everything (V2X)
communications in autonomous vehicles and cybersecurity schemes, while its code
is freely available to the public.
