On 8/9/2025 10:14 PM, Bob Carlson wrote: > I am thinking of that cross section in terms of [x, 0, z]. OK.  That would require that polygon() allow you to specify points in 3-space, which it currently does not allow.  Right? (And then there would be questions about getting the points to be coplanar, which is easy to do precisely if you're axis-aligned, but less easy if not.) Sounds like fodder for OEP7: Mixed Dimension Geometry Support <https://github.com/openscad/openscad/wiki/OEP7:-Mixed-Dimension-Geometry-Support>, if anybody ever takes that on. It does *not* sound like you care about the case where you've created something using the 2D primitives (and so it lies in the Z=0 plane) and you've then moved the 2D object out of the Z=0 plane and extruded it.  Right?