  We present Deimos, a grammar for specifying dynamic embodied immersive
visualisation morphs and transitions. A morph is a collection of animated
transitions that are dynamically applied to immersive visualisations at runtime
and is conceptually modelled as a state machine. It is comprised of state,
transition, and signal specifications. States in a morph are used to generate
animation keyframes, with transitions connecting two states together. A
transition is controlled by signals, which are composable data streams that can
be used to enable embodied interaction techniques. Morphs allow immersive
representations of data to transform and change shape through user interaction,
facilitating the embodied cognition process. We demonstrate the expressivity of
Deimos in an example gallery and evaluate its usability in an expert user study
of six immersive analytics researchers. Participants found the grammar to be
powerful and expressive, and showed interest in drawing upon Deimos' concepts
and ideas in their own research.
