Efficient Clipping plane method in conduit


I need to write a routine that allows my users to grab a bunch of geometry, and waterline it as the mouse moves over the geometry in a z direction. I tried intersect, but if the geometry is not bolleaned it gives strange results and the overhead on 3-400 bits of geometry is high, super sluggish.

clipping plane does what i need, and its very fast, so id like to grab existing geometry, set it to transparent (the easy part) then copy it to conduit, and apply a clipping plane in the conduit, marry clipping plane of the existing geometry, so that the exposed (perhaps bright yellow) conduit clipped geometry shadows the main geometry and effectively provides a fast “waterline”.

Im stumped on how to pull this off, or if its even the best way?

output desired is something along these lines from the b9 creator software.

any thoughts?