Specular Maps Query

[cw8]

Working on this atm, something I made for Simcity 4's BAT back in 2004. I want to create the specular map for it but the Wiki isn't exactly clear on the instructions. Pure 100% white for windows. I've tried it but it looks weird and the whole building becomes reflective. What colour do I use to make parts I want to be dull and non-reflective? I assume it's black or do I simply not put any colour and leave it blank? I assume the lighter the colour, the more reflective stuff gets?
Also, how does illumination maps work?

 

[OlaHaldor]

If it works anything like opacity maps does, it's either fully reflective, or not reflective at all. Anything in between may give weird results. I honestly haven't given it much thought and always made windows pure white to make them reflective.


Reflective = pure white
Dull = pure black