  In the field of distributed computing by robot swarms, the research
comprehends manifold models where robots operate in the Euclidean plane through
a sequence of look-compute-move cycles. Models under study differ for (i) the
possibility of storing constant-size information, (ii) the possibility of
communicating constant-size information, and (iii) the synchronization mode. By
varying features (i,ii), we obtain the noted four base models: OBLOT (silent
and oblivious robots), FSTA (silent and finite-state robots), FCOM (oblivious
and finite-communication robots), and LUMI (finite-state and
finite-communication robots). Combining each base model with the three main
synchronization modes (fully synchronous, semi-synchronous, and asynchronous),
we obtain the well-known 12 models. Extensive research has studied their
computational power, proving the hierarchical relations between different
models. However, only transparent robots have been considered. In this work, we
study the taxonomy of the 12 models considering collision-intolerant opaque
robots. We present six witness problems that prove the majority of the
computational relations between the 12 models. In particular, the last witness
problem depicts a peculiar issue occurring in the case of obstructed visibility
and asynchrony.
