Virtual reality (VR) environments are increasingly being addressed by
Human-Computer Interaction researchers and practitioners, due to the recent and
rapid development of affordable hardware targeted to the mass market. In that
respect, implicit interactions are the go-to paradigm for conceiving VR
applications, particularly in simulation and gaming. However, to the best of
our knowledge, there is still a significant gap in literature regarding models
and practical guidelines to assist designers and software developers when
building interactive applications in this domain. As a way to provide a common
ground for designing interactive applications in VR environments, this paper
presents a formal conceptualization of implicit interaction mechanisms. To do
so, we propose a set of formal models and we show a working example
implementing such interaction mechanisms in an interactive visual novel, i.e.,
a video game comprising a compelling narrative extended by the interaction
within an immersive environment, which in this case corresponds to a VR world.
As a way to gauge user acceptance of the produced video game, we conducted a
controlled user study measuring perceived immersion and player experience with
a particular focus in the implementation of the proposed implicit interaction
mechanisms. The obtained results are highly promising, highlighting the
understandability and flexibility of the proposed mechanisms.