Issue description
I have noticed that every block that is cutout block is not allowing light to go threw and generates dark shadow if they are placed in 2x2 pattern or other example if we use custom glass block it will allow to see threw but if we use our block to cover any light source in room it will not allow any light to pass threw just like normal blocks but and yes setting up blocks opacity does not help :L
In such case, use transparent blocks instead, this is how cutout blocks behave.