Started with walls...
x3d standalone PoC and Shiny-Integration

x3dom-poc.xhtml is a standalone PoC implementation that works fine.
xhtml is required by the xdom to make Timers, Interpolators, etc.
advanced stuff working.
Had a first go at integrating x3dom-poc.html into zrr.shiny.dev project,
without success. x3d content does not get rendered. Besides, I have not
found out how to make shiny create xhtml instead of just html output, i.e.
the advanced stuff would not work anyway...