I'm just trying to undaerstand it by reading some articles and sample codes, and trying to get what they can get.
e.g. there is a nice example using 6 lightmaps and combining their shadows.

edit1:
but I'm a bit got stuck, as it does not work as I expected... and in the original depth shader it is commented out... need some further research, but I don't understand the distance calculations in shade-c...