Quote - Since I'll be working on the light exporter today, timing here is perfect.

We could go two ways. Or both.

1) Name the lights like this: GroupName:LightName. For example:
 

Foyer:Spot1, Foyer:Spot2, Foyer:Spot3

Hall:Bulb

Living Room:Lamp1, LivingRoom:Lamp2

This would give you three groups to play with.

2. I make lists of lights in the export configuration file and provide a drag-and-drop GUI to create light groups regardless of name.

1+2) Groups are automatically created from the naming convention, but then can be joined/split through the export config tool.

Be aware that option 2 is a lot more work. It's more parameters to parse and more stuff in the GUI. Also, figuring out how to save that grouping info in the scene is tough.

Options...wow all I have been doing is going into the test.lxs and just naming the group after the light...

Quote -

start light "Light 1"

AttributeBegin
LightGroup "Light 1"
LightSource "spot"
"color L" [0.997 0.983 0.996 ]
"float gain" [921.600]
"point from" [-1.28401041 1.34252071 1.48603559 ]
"point to" [1.00000000 1.00000000 30.00000000 ]
"float coneangle" [70.000]
"float conedeltaangle" [70.000]
AttributeEnd

 
Which works fine for me (some may want a little more control over naming) so whatever is easiest to code for you in a convention you like is what I'll take

As for materials, the exporter (Baggins) posted is the one I used most recently and it choked on a scene (I expected it to, it was really big) but a one figure + backdrop came out just fine including the materials (backdrop was blown out, I'll play with it again to see if it was material or lighting).