[Nel] about cluster systems

[Francois DUSSAUGE]

hi,

I tried to make your cluster viewer sample work. It works since I have only one 
IG, but when I try to use a hierarchy of cluster systems (ie more than one IG, 
like in your example with a landscape and a house "street.ig"), it doesn't work 
: all the shapes in the IG son are apparent from the father. Even if I put all 
the flags as you say in the readme file, it crashes. 
I followed your documentation "cluster system v2", but maybe I must do anything 
else in order to use a hierarchy of cluster systems?

thanks