Clipping a mesh against a plane

I can’t find one but is there a method anywhere to create a geometry for a mesh clipped against a plane?

Basically I want to create a mesh from a height map and then clip it at an arbitrary height. I have been able to remove the triangles which are on the floor of the plane, but without proper clipping, that creates in fill triangles, its going to be too blocky.

Is there something I can use or is it time for me to get out the 3d programming for dummies and try to remember my vector maths :?

Sorry, nothing in jME currently to handle this for you.

by the way, is there any easy solution to clip for example box b from sphere s?

I supose there is no, but that would be very usefull… at least to me.