January 30, 2012, 10:56:55 pm
Mirror effects require planar reflection that are not currently supported by Lumion.
There's a number of topics on this including response from Morten and Remko, please search the forum.
There's various workarounds and one or two users have some examples in the forum.
You can also use fake mirror reflections, not anywhere perfect but may get you by, depending on scene requirements.