I have been tinkering with making a real time mirror and I have tried a few different methods with lighting and achieving the mirror itself.
I have landed on Lightmass with RT standalone reflections, this is giving me best results for looks and fps.
My current issues is I want the lights to be able to turn on and off in the bathroom, so I have movable lights in the bathroom. I am using a spotlight with cast shadows for the main light. I am also using a point light without cast shadows for a fill light.
However, the point light is still showing cast shadows in the reflection. You can see with the cube and the guy.
Here is my post process ray trace settings
I hope it is just a check box somewhere that I am not aware of, and not a limitation to this method.