Currently I am not aware of levels that make use of such doors (except the prison/Guidebot doors but they are more "destroyable walls")... you are talking about some custom levels, right? As it may be: I will consider such cases anyways - if a texture has transparent parts, the light will go through.
The greatest pleasure in life is to do what people say you cannot do.
Uhm... Honey, there's a head in the toilet!
Uhm... Honey, there's a head in the toilet!