I'm trying to fit a bottlecap to the decorative bottle shown in the photo below. The owner lost the cap but doesn't want to discard such a lovely bottle. I have a 3D printer, so I said I would design and print a new bottlecap. As part of the fitting process, I tried to create a bottlecap with threads that 'cut through' the cap material so that I could visually see how the bottlecap 'innie' threads match up with the bottlecap 'outie' threads. Imagine my surprise when, after generating the model I wanted, the rendering process completely obliterated the threads, the cuts, and everything else, resulting in a solid cylinder of material.
Here are some some screenshots showing the problem:
F5 preview of 'normal' thread geometry
Render operation for 'normal' geometry
F5 preview of 'cut through' thread geometry
Render operation for 'cut through' geometry
And here is the code that produced the above geometries: