3d voronoi and brep intersections ?

Hi All,

I'm having a struggle with something that I feel should be really simple...but I just can't get it!

I'm intersecting a brep with some voronoi cells, but what I'm after (and can't seem to get) is just the lines left from the voronoi that intersects directly with the surface of the brep (i.e. just the visible green lines shown on the brebs surface here). so what I am left with is a skin/surface with the voronoi cell pattern imprinted on it...hope this makes sense?

Any help would be amazing! 

Many thanks!