Hi guys I have been trying to generate floor slabs from a topo by extracting the list of points etc but not sure why my ‘List’ is showing Empty on the Geometry Intersect node.

Any help?

I don’t know either, but might I suggest another approach?

You have a Polysurface representing the Topo. Extract the Perimeter Curves using Surface.PerimeterCurves and pull those curves onto the XY Plane using Curve.PullOntoPlane. I assume this will give you the same result you are looking for.