Just use the “mesh shadow” component from the other day, but change the plane and direction.
Actually, the MeshSection method will work better than the shadow because it’s faster here and it’ll skip duplicate silhouettes.
See here:
Meshcrosssection.gh (44.4 KB)
BUT, if you only want the OUTER region, then unify it with RUnion:
Meshcrosssection-outer-region.gh (48.3 KB)
Note:
Similar to your other post, the important thing is to query your rhino objects, which includes the blocks but also other objects; most can be ignored and you’d still grab the mesh section, but the data might be a little dirty, that’s why I still took curves out (see TextMatch component).