Voronoi Stadium space frame Design


I’m a student and for Design Studio I want to create an organic voronoi space frame around an existing stadium.
I’ve managed to use voronoi for a basic cube, but when I try it on my
desired shape around the stadium, which is a closed solid polygon, the voronoi structure isn’t created inside the absolute boundary, but more like inside an overall boundary (see pictures)
Any help on how to achieve this? Also, is it possible to assign inner boundaries where you DON’t want any structure?

Thanks a lot in advance!!!
Stay healthy,

boundaryVolumeforStadiumShell.3dm (509.8 KB)
shell test.gh (5.2 KB)