Does HFSS visualize the field in real-time or a user needs to set the geometry/parameters then precalculate the field and only then be able to explore the visualization?

Say, if I wanted to see immediate effects of changing an incidence angle, could I just "scroll" the incidence parameter?

HFSS does a typical FEM matrix solve then displays the results. It is often used for very complex or large problems, so as far as I know it isn’t set up for instant display of results. That would be a neat feature for small problems.