Ember use MediaInfo to read the embedded MKV headers.
You can check the Meta Data if Ember has recognized the 3d mode:
MKV provides most or all known 3d modes, but not all mkv's has set this informations. You have to set it manually in Embers Meta Data Editor or (better) with an MKV editor, ff the 3d informations are missing.
Kodi needs the "3d" and "sbs" or tab "flag" to recognize a file as 3d media. As always, Kodi try to read the header information directly from file while playback and write that info to the Kodi database.
The Renamer module in Ember can only set the "3D" flag after a simple check: If MultiViewCount greater then 1 => write 3D, else => write empty string.
If will add new $ tag for short version of "StereoMode" to convert "buttom_top" to "tab" and "left_right" to "sab". Half or not half whill be ignored, i have no idea how we can get this information from mkv.
There are many
other 3d modes, but i have also no idea what Kodi needs as flag to recognize them.