  Augmented Reality (AR) provides a safe and low-cost option for hazardous
safety training that allows for the visualization of aspects that may be
invisible, such as radiation. Effectively visually communicating such threats
in the environment around the user is not straightforward. This work describes
visually encoding radiation using the spatial awareness mesh of an AR Head
Mounted Display. We leverage the AR device's GPUs to develop a real time
solution that accumulates multiple dynamic sources and uses stencils to prevent
an environment being over saturated with a visualization, as well as supporting
the encoding of direction explicitly in the visualization. We perform a user
study (25 participants) of different visualizations and obtain user feedback.
Results show that there are complex interactions and while no visual
representation was statistically superior or inferior, user opinions vary
widely. We also discuss the evaluation approaches and provide recommendations.
