I found out light doesn’t go through glasses in both internal renderer and cycles,
I rummaged some information and finally figured out that I have to turn off shadow options to make light penetrate transparent things.
I tested it myelf. With both iternal renderer and cycles, light doesn’t penetrate glasses if I use shadow option.
…So I have to use at least two lights to make ‘sunlight shines through my window’?
One is penetrating light from outside, one is an indoor light creating shadows?